Debt Disclosure [Abstract] Debt Debt Disclosure [Text Block] Document And Entity Information [Abstract] Document and entity information. Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Public Float Entity Public Float Other Liabilities Disclosure [Abstract] Composition of Other Liabilities, Net Other Liabilities [Table Text Block] Segment Reporting [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Share-Based Compensation Related To Formation Transaction [Member] Share-Based Compensation Related To Formation Transaction [Member] Share-Based Compensation Related To Formation Transaction [Member] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Business Acquisition [Line Items] Business Acquisition [Line Items] Net income (loss) attributable to common shareholders Net Income (Loss) Attributable to Parent Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Corporate and other Other General and Administrative Expense Third-party real estate services Management Fee Expense Share-based compensation related to Formation Transaction Allocated Share-based Compensation Expense Allocated Share-based Compensation Expense - Formation Transaction Allocated Share-based Compensation Expense - Formation Transaction Allocated Share-based Compensation Expense - Formation Transaction Transaction and other costs Business Combination, Acquisition Related Costs Interest expense Interest Expense Income tax expense (benefit) Income Tax Expense (Benefit) Third-party real estate services, including reimbursements Management Fees Revenue Other income Other Income Income (loss) from unconsolidated real estate ventures, net Income (Loss) from Equity Method Investments Interest and other income, net Investment Income, Net Gains (Losses) on Sales of Investment Real Estate Gains (Losses) on Sales of Investment Real Estate Net loss attributable to redeemable noncontrolling interests Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Net loss attributable to noncontrolling interests Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest Consolidated NOI Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Equity Method Investments and Joint Ventures [Abstract] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Canadian Pension Plan Investment Board (CPPIB) Canadian Pension Plan Investment Board [Member] Canadian Pension Plan Investment Board [Member] Landmark Landmark [Member] Landmark [Member] CBREI Venture CBREI Venture [Member] CBREI Venture [Member] Berkshire Group [Member] Berkshire Group [Member] Berkshire Group [Member] Brandywine Brandywine [Member] Brandywine [Member] MRP Realty [Member] MRP Realty [Member] MRP Realty [Member] CIM/PacLife [Member] CIM/PacLife [Member] CIM/PacLife JP Morgan JP Morgan [Member] JP Morgan [Member] Other Other Investment [Member] Other Investment [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Ownership Interest Equity Method Investment, Ownership Percentage Total investments in unconsolidated real estate ventures Real Estate Investments, Unconsolidated Real Estate and Other Joint Ventures, Excluding Advances Real Estate Investments, Unconsolidated Real Estate and Other Joint Ventures, Excluding Advances Advances to unconsolidated real estate ventures Real Estate Investments, Unconsolidated Real Estate and Other Joint Ventures, Advances Real Estate Investments, Unconsolidated Real Estate and Other Joint Ventures, Advances Total investments in and advances to unconsolidated real estate ventures Real Estate Investments, Unconsolidated Real Estate and Other Joint Ventures Fair Value Disclosures [Abstract] Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of Financial Instruments and Liabilities as Reflected on Balance Sheet Fair Value, by Balance Sheet Grouping [Table Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] LTIP and Time-Based LTIPs Long-Term Incentive Partnership Units And Time-Based Long-Term Incentive Partnership Units [Member] Long-Term Incentive Partnership Units And Time-Based Long-Term Incentive Partnership Units [Member] Time-Based LTIP Units Time-Based Long-Term Incentive Partnership Units [Member] Time-Based Long-Term Incentive Partnership Units [Member] Vesting [Axis] Vesting [Axis] Vesting [Domain] Vesting [Domain] Vesting Period One Share-based Compensation Award, Tranche One [Member] Vesting Period Two Share-based Compensation Award, Tranche Two [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract] Equity grants (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Fair value of awards on grant date Deferred Compensation Arrangement with Individual, Fair Value of Shares Issued Percentage of vesting rights for each tranche Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Number of installments Share-Based Compensation Arrangement By Share-Based Payment Award, Award Vesting Rights, Number Of Installments Share-Based Compensation Arrangement By Share-Based Payment Award, Award Vesting Rights, Number Of Installments Compensation expense recognition period (in years) Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Expected volatility rate Fair Value Assumptions, Expected Volatility Rate Risk-free interest rate Fair Value Assumptions, Risk Free Interest Rate Expected life (in years) Fair Value Assumptions, Expected Term Weighted Average Grant-Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Earnings Per Share [Abstract] Earnings (Loss) Per Common Share Earnings Per Share [Text Block] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Legacy JBG Funds [Member] Legacy JBG Funds [Member] Legacy JBG Funds [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Marriott Wardman Park Hotel [Member] Marriott Wardman Park Hotel [Member] Marriott Wardman Park Hotel [Member] 1900 N Street 1900 N Street [Member] 1900 N Street [Member] Investments in Joint Ventures Investments in Joint Ventures Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Excludes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership. Long-term Purchase Commitment, Amount Long-term Purchase Commitment, Amount Payments to Acquire Interest in Joint Venture Payments to Acquire Interest in Joint Venture Equity Method Investment, Ownership Percentage After Funding Of Contributions Equity Method Investment, Ownership Percentage After Funding Of Contributions Equity Method Investment, Ownership Percentage After Funding Of Contributions Statement of Financial Position [Abstract] Preferred shares, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred shares, shares authorized Preferred Stock, Shares Authorized Preferred shares, shares issued Preferred Stock, Shares Issued Preferred shares, shares outstanding Preferred Stock, Shares Outstanding Common shares, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common shares, shares authorized Common Stock, Shares Authorized Common shares, shares issued Common Stock, Shares, Issued Common shares, shares outstanding Common Stock, Shares, Outstanding Noncontrolling Interest [Abstract] Noncontrolling Interest [Table] Noncontrolling Interest [Table] JBG Smith, LP JBG Smith, LP [Member] JBG Smith, LP [Member] Consolidated Real Estate Venture Consolidated Real Estate Venture [Member] Consolidated Real Estate Venture [Member] Noncontrolling Interest [Line Items] Noncontrolling Interest [Line Items] Temporary Equity Increase (Decrease) in Temporary Equity [Roll Forward] Beginning Balance Redeemable Noncontrolling Interest, Equity, Carrying Amount Net loss attributable to redeemable noncontrolling interests Temporary Equity, Net Income Other comprehensive income Temporary Equity, Other Comprehensive Income (Loss) Temporary Equity, Other Comprehensive Income (Loss) Share-based compensation expense Temporary Equity, Share-based Compensation Temporary Equity, Share-based Compensation Temporary Equity, Accretion to Redemption Value Temporary Equity, Carrying Amount, Period Increase (Decrease) Ending Balance Organization, Consolidation and Presentation of Financial Statements [Abstract] Variable Interest Entities Variable Interest Entity Disclosure [Text Block] Accounting Policies [Abstract] Schedule of Recent Accounting Pronouncements Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] OP Units Common Limited Partnership Units [Member] Common Limited Partnership Units [Member] Formation Awards Formation Awards [Member] Formation Awards [Member] LTIP and OP Units (1) Performance-Based LTIP Units Performance Shares [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive securities excluded from computation of earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract] Summary of Other Assets, net Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table Text Block] Interest Expense [Abstract] Interest Income and Interest Expense Disclosure [Text Block] Interest Income and Interest Expense Disclosure [Text Block] Share-Based Payments and Employee Benefits Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Line of Credit Facility [Table] Line of Credit Facility [Table] Line of credit Line of Credit [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving credit facility Revolving Credit Facility [Member] Tranche A-1 Term Loan Tranche A-1 Term Loan Credit Facility [Member] Tranche A-1 Term Loan Credit Facility [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Interest Rate (1) Debt Instrument, Interest Rate, Stated Percentage Long-term debt, gross Long-term Debt, Gross Unamortized deferred financing costs, net Debt Issuance Costs, Net Debt, net Long-term Debt Letters of credit Letters of Credit Outstanding, Amount Debt Issuance Costs, Line of Credit Arrangements, Net Debt Issuance Costs, Line of Credit Arrangements, Net Statement of Cash Flows [Abstract] Capitalized interest Interest Paid, Capitalized Interest Costs Capitalized Interest Costs Capitalized - Mortgages Payable Deferred Interest Interest Costs Capitalized - Mortgages Payable Deferred Interest Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] OP Units OP Units [Member] OP Units [Member] Common shares and OP Units issued in consideration Business Acquisition, Equity Interest Issued or Issuable, Number of Shares Ownership interest by parent Noncontrolling Interest, Ownership Percentage by Parent Ownership interest by parent, threshold for capital contributions to cease Noncontrolling Interest, Capital Contribution Threshold, Ownership Percentage by Parent Noncontrolling Interest, Capital Contribution Threshold, Ownership Percentage by Parent Redemption period Redeemable Noncontrolling Interest, Redemption Period Redeemable Noncontrolling Interest, Redemption Period Investments in and Advances to Unconsolidated Real Estate Ventures Equity Method Investments and Joint Ventures Disclosure [Text Block] Commitments and Contingencies Disclosure [Abstract] Deferred leasing costs Deferred Costs, Leasing, Gross Accumulated amortization Deferred Costs, Leasing, Accumulated Amortization Deferred leasing costs, net Deferred Costs, Leasing, Net Prepaid expenses Prepaid Expense Identified intangible assets, net Intangible Assets, Net (Excluding Goodwill) Deferred financing costs on revolving credit facility, net Deposits Deposit Assets Derivative Instruments in Hedges, Assets, at Fair Value Derivative Instruments in Hedges, Assets, at Fair Value Other Other Assets, Miscellaneous Total other assets, net Other Assets OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities [Abstract] Net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Adjustments to reconcile net income (loss) to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Share-based compensation expense Share-based Compensation Depreciation and amortization, including amortization of debt issuance costs Depreciation, Depletion and Amortization Deferred rent Straight Line Rent (Income) loss from unconsolidated real estate ventures, net Amortization of above- and below-market lease intangibles, net Amortization Of Acquired Below-Market Lease, Net Of Acquired Above-Market Lease Amortization Of Acquired Below-Market Lease, Net Of Acquired Above-Market Lease Amortization of lease incentives Amortization of Lease Incentives Return on capital from unconsolidated real estate ventures Proceeds from Equity Method Investment, Distribution Gain on sale of real estate Unrealized gain on interest rate swaps and caps Unrealized Gain (Loss) on Derivatives Bad debt expense Provision for Doubtful Accounts Other non-cash items Other Noncash Income (Expense) Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Tenant and other receivables Increase (Decrease) in Accounts and Notes Receivable Other assets, net Increase (Decrease) in Other Operating Assets Accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Other liabilities, net Increase (Decrease) in Other Operating Liabilities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities INVESTING ACTIVITIES: Net Cash Provided by (Used in) Investing Activities [Abstract] Development costs, construction in progress and real estate additions Payments to Acquire and Develop Real Estate Proceeds from sale of real estate Proceeds from Sale of Real Estate Held-for-investment Acquisition of interests in unconsolidated real estate ventures, net of cash acquired Payments to Acquire Equity Method Investments Distributions of capital from unconsolidated real estate ventures Proceeds from Equity Method Investment, Distribution, Return of Capital Investments in and advances to unconsolidated real estate ventures Payments to Acquire Real Estate and Real Estate Joint Ventures Other investments Payments to Acquire Other Investments Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities [Abstract] Contributions from former parent, net Proceeds from Contributions from Affiliates Payments for (Proceeds from) Other Real Estate Partnerships Payments for (Proceeds from) Other Real Estate Partnerships Proceeds from borrowings from former parent Proceeds from Related Party Debt Capital lease payments Repayments of Long-term Capital Lease Obligations Borrowings under mortgages payable Proceeds from Notes Payable Borrowings under unsecured term loan Proceeds from Issuance of Unsecured Debt Repayments of mortgages payable Repayments of Notes Payable Debt issuance costs Payments of Debt Issuance Costs Dividends paid to common shareholders Payments of Ordinary Dividends, Common Stock Distributions to redeemable noncontrolling interests Payments of Ordinary Dividends, Noncontrolling Interest Distributions to noncontrolling interests Payments to Noncontrolling Interests Net cash (used in) provided by financing activities Net Cash Provided by (Used in) Financing Activities Net (decrease) increase in cash and cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash and cash equivalents and restricted cash as of beginning of the period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash and cash equivalents and restricted cash as of end of the period CASH AND CASH EQUIVALENTS AND RESTRICTED CASH AS OF END OF THE PERIOD: Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted cash Restricted Cash Cash and cash equivalents and restricted cash SUPPLEMENTAL DISCLOSURE OF CASH FLOW AND NON-CASH INFORMATION: Supplemental Cash Flow Information [Abstract] Cash paid for interest (net of capitalized interest of $4,516 and $455 in 2018 and 2017) Interest Paid, Net Accrued capital expenditures included in accounts payable and accrued expenses Capital Expenditures Incurred but Not yet Paid Write-off of fully depreciated assets Write-Off Of Fully Depreciated Assets, Including Asset Impairment Write-Off Of Fully Depreciated Assets, Including Asset Impairment Deferred interest on mortgages payable (of which $941 is included in capitalized interest) Interest Payable Cash payments for income taxes Income Taxes Paid Net loss attributable to redeemable noncontrolling interests Net loss attributable to noncontrolling interests NET INCOME (LOSS) ATTRIBUTABLE TO COMMON SHAREHOLDERS Weighted average number of shares outstanding - basic and diluted ( in shares) Weighted Average Number of Shares Outstanding, Basic and Diluted Earnings (loss) per common share: Earnings Per Share, Diluted [Abstract] Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating Segments Operating Segments [Member] Elimination of Intersegment Activity Consolidation, Eliminations [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Office Office Segment [Member] Office Segment [Member] Multifamily Multifamily segment [Member] Multifamily segment [Member] Other Other Segments [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Property rentals Operating Leases, Income Statement, Lease Revenue Tenant reimbursements Tenant Reimbursements Total rental revenue Revenue, Net Property operating Cost of Other Property Operating Expense Real estate taxes Real Estate Tax Expense Total rental expense Operating Leases, Rent Expense Consolidated NOI Other Equity Awards Other Equity Awards [Member] Other Equity Awards [Member] Share-based compensation expense - other Share-Based Compensation, Other [Member] Share-Based Compensation, Other [Member] Share-based compensation related to Formation Transaction Less amount capitalized Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount Share-based compensation expense Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost Total unrecognized compensation expense Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options Conversion of OP Units Conversion Of Common Limited Partnership Units [Member] Conversion Of Common Limited Partnership Units [Member] Third-Party Real Estate Services Segment Third-Party Real Estate Services Segment [Member] Third-Party Real Estate Services Segment [Member] Number of reportable segments Number of Reportable Segments Number of operating segments Number of Operating Segments Other assets, net ASSETS Assets [Abstract] Real estate, at cost: Real Estate Investment Property, at Cost [Abstract] Land and improvements Land and Land Improvements Buildings and improvements Investment Building and Building Improvements Construction in progress, including land Development in Process Real estate, at cost Real Estate Investment Property, at Cost Less accumulated depreciation Real Estate Investment Property, Accumulated Depreciation Real estate, net Real Estate Investment Property, Net Cash and cash equivalents Restricted cash Tenant and other receivables, net Accounts and Notes Receivable, Net Deferred rent receivable, net Deferred Rent Receivables, Net Investments in and advances to unconsolidated real estate ventures Assets Held-for-sale, Not Part of Disposal Group Assets Held-for-sale, Not Part of Disposal Group TOTAL ASSETS Assets LIABILITIES, REDEEMABLE NONCONTROLLING INTERESTS AND EQUITY Liabilities and Equity [Abstract] Liabilities: Liabilities [Abstract] Mortgages payable, net Secured Debt Revolving credit facility Long-term Line of Credit Unsecured term loan, net Unsecured Debt Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities Other liabilities, net Other Liabilities Liabilities held for sale Liabilities held for sale Liabilities held for sale Total liabilities Liabilities Commitments and Contingencies Commitments and Contingencies Redeemable noncontrolling interests Shareholders' equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Preferred shares, $0.01 par value - 200,000 shares authorized, none issued Preferred Stock, Value, Issued Common shares, $0.01 par value - 500,000 shares authorized and 117,955 shares issued and outstanding as of March 31, 2018 and December 31, 2017 Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Accumulated deficit Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Shareholders' equity / Former parent equity Stockholders' Equity Attributable to Parent Noncontrolling interests in consolidated subsidiaries Stockholders' Equity Attributable to Noncontrolling Interest Total equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest TOTAL LIABILITIES, REDEEMABLE NONCONTROLLING INTERESTS AND EQUITY Liabilities and Equity Summary of Share-Based Compensation Expense Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Fair Value Measurements Fair Value Disclosures [Text Block] Business Acquisition, Pro Forma Information [Table Text Block] Business Acquisition, Pro Forma Information [Table Text Block] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Mortgages payable Mortgages [Member] Tranche A-2 Term Loan Tranche A-2 Term Loan Credit Facility [Member] Tranche A-2 Term Loan Credit Facility [Member] Net carrying value of real estate collateralizing the mortgages payable Debt Instrument, Collateral Amount Repayment of mortgages payable Repayments of Secured Debt Derivative, notional amount Derivative, Notional Amount Credit facility, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Borrowings under revolving credit facility Proceeds from Lines of Credit Number of debt extension options Debt Instrument, Number Of Term Extension Options Debt Instrument, Number Of Term Extension Options Debt extension option period (in months) Debt Instrument, Extension Option, Term Debt Instrument, Extension Option, Term Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Segment Information Segment Reporting Disclosure [Text Block] Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] LTIP Units [Member] LTIP Units [Member] LTIP Units [Member] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Reston, Virginia Reston, Virginia [Member] Reston, Virginia [Member] Summit I & II Land [Member] Summit I & II Land [Member] Summit I & II Land [Member] Bowen Building, Washington DC [Member] Bowen Building, Washington DC [Member] Bowen Building, Washington DC [Member] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Office Assets Office Equipment [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Common Stock, Dividends, Per Share, Declared Common Stock, Dividends, Per Share, Declared Carrying value of office asset Property, Plant and Equipment, Net Gross sales price Proceeds from Sale of Property Held-for-sale Repayments of Secured Debt Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Not Primary Beneficiary Variable Interest Entity, Not Primary Beneficiary [Member] Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Assets Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets Liabilities Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities Number of Real Estate Properties Number of Real Estate Properties Basis of Accounting [Text Block] Basis of Accounting [Text Block] Business Combinations Policy [Policy Text Block] Business Combinations Policy [Policy Text Block] Reclassification, Policy [Policy Text Block] Reclassification, Policy [Policy Text Block] Variable rate, weighted average interest rate Equity Method Investment, Long Term Debt, Percentage Bearing Variable Interest, Percentage Rate Equity Method Investment, Long Term Debt, Percentage Bearing Variable Interest, Percentage Rate Variable rate Equity Method Investment, Long Term Debt, Bearing Variable, Amount Equity Method Investment, Long Term Debt, Bearing Variable, Amount Fixed rate, weighted average interest rate Equity Method Investment, Long Term Debt, Percentage Bearing Fixed Interest, Percentage Rate Equity Method Investment, Long Term Debt, Percentage Bearing Fixed Interest, Percentage Rate Fixed rate Equity Method Investment, Long Term Debt, Bearing Fixed, Amount Equity Method Investment, Long Term Debt, Bearing Fixed, Amount Unconsolidated real estate ventures - mortgages payable Equity Method Investment, Long Term Debt Equity Method Investment, Long Term Debt Unamortized deferred financing costs Equity Method Investment, Unamortized Deferred Financing Costs Equity Method Investment, Unamortized Deferred Financing Costs Unconsolidated real estate ventures - mortgages payable, net Equity Method Investment, Long Term Debt, Net Equity Method Investment, Long Term Debt, Net Segment information Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Other Liabilities [Table] Schedule of Other Liabilities [Table] Schedule of Other Liabilities [Table] Landmark [Member] 1101 17th Street [Member] 1101 17th Street [Member] Schedule of Other Liabilities [Line Items] Schedule of Other Liabilities [Line Items] [Line Items] for Schedule of Other Liabilities [Table] Lease intangible liabilities Below Market Lease, Gross Accumulated amortization Below Market Lease, Accumulated Amortization Lease intangible liabilities, net Below Market Lease, Net Prepaid rent Advance Rent Lease assumption liabilities and accrued tenant incentives Lease Assumptions Liabilities And Accrued Tenant Incentives Lease Assumptions Liabilities And Accrued Tenant Incentives Capital lease obligation Capital Lease Obligations Security deposits Security Deposit Liability Ground lease deferred rent payable Deferred Rent Credit Net deferred tax liability Deferred Income Tax Liabilities, Net Dividends payable Dividends Payable Obligation due to unconsolidated real estate venture partner Obligation due to unconsolidated real estate venture partner Obligation due to unconsolidated real estate venture partner Other Other Sundry Liabilities Total other liabilities, net Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Fair value of awards on grant date (in dollars per unit) Deferred Compensation Arrangement with Individual, Fair Value of Shares Issued, Per Unit Deferred Compensation Arrangement with Individual, Fair Value of Shares Issued, Per Unit Dividend yield rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Redeemable Noncontrolling Interests Redeemable Noncontrolling Interest [Table Text Block] Other Assets, Net Other Assets Disclosure [Text Block] Composition of Investments Equity Method Investments [Table Text Block] Redeemable Noncontrolling Interests Temporary Equity Disclosure [Text Block] Temporary Equity Disclosure [Text Block] Other Liabilities, Net Other Liabilities Disclosure [Text Block] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Real estate, at cost Real Estate Held-for-sale Real Estate Held-for-sale Total assets (1) Use of Estimates, Policy [Policy Text Block] Use of Estimates, Policy [Policy Text Block] New Accounting Pronouncements, Policy [Policy Text Block] New Accounting Pronouncements, Policy [Policy Text Block] Subsequent Events Subsequent Events [Text Block] Schedule of Real Estate Properties [Table] Schedule of Real Estate Properties [Table] Real Estate Property Ownership [Axis] Real Estate Property Ownership [Axis] Real Estate Properties [Domain] Real Estate Properties [Domain] Consolidated Properties Consolidated Properties [Member] Unconsolidated Properties Unconsolidated Properties [Member] Real Estate Properties [Line Items] Real Estate Properties [Line Items] General liability insurance limit General Liability Insurance Coverage Limit, Per Occurrence General Liability Insurance Coverage Limit, Per Occurrence Property and rental value insurance coverage limit Property and Rental Value Insurance Coverage Limit Property and Rental Value Insurance Coverage Limit Terrorist acts insurance coverage limit Terrorist Acts Insurance Coverage Limit, Per Occurrence Terrorist Acts Insurance Coverage Limit, Per Occurrence Purchase obligation Purchase Obligation Commitment amortization period Commitment Amortization Period Commitment Amortization Period Principal payment guarantees Guarantor Obligations, Maximum Exposure, Undiscounted Additional capital funding committed amount Other Commitment Organization and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Unsecured term loan Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Carrying Amount Reported Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Financial liabilities: Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Financial liabilities Debt Instrument, Fair Value Disclosure Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Capitalization of internal leasing costs Deferred Costs, Internal Leasing, Net Deferred Costs, Internal Leasing, Net Contractual Obligation Ground lease contractual obligation Ground lease contractual obligation Statement of Comprehensive Income [Abstract] NET INCOME (LOSS) Other Comprehensive Income (Loss), Net of Tax [Abstract] Other Comprehensive Income (Loss), Net of Tax [Abstract] Change in fair value of derivative financial instruments Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Reclassification of net loss on derivative financial instruments from accumulated other comprehensive income into interest expense Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax Other comprehensive income Other Comprehensive Income (Loss), Net of Tax COMPREHENSIVE INCOME Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Other comprehensive income attributable to redeemable noncontrolling interests Comprehensive Income (Loss), Net Of Tax, Attributable To Redeemable Noncontrolling Interest Comprehensive Income (Loss), Net Of Tax, Attributable To Redeemable Noncontrolling Interest Comprehensive loss attributable to noncontrolling interests Comprehensive Income (Loss), Net Of Tax, Attributable To Nonredeemable Noncontrolling Interest Comprehensive Income (Loss), Net Of Tax, Attributable To Nonredeemable Noncontrolling Interest COMPREHENSIVE INCOME ATTRIBUTABLE TO JBG SMITH PROPERTIES Comprehensive Income (Loss), Net of Tax, Attributable to Parent Statement [Table] Statement [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Statement [Line Items] Statement [Line Items] Interest expense Interest Expense, Debt, Excluding Amortization Amortization of deferred financing costs Amortization of Debt Discount (Premium) Capitalized interest Interest Expense Income Statement [Abstract] REVENUE Revenues [Abstract] Total revenue Revenues EXPENSES Costs and Expenses [Abstract] General and administrative: General and Administrative Expense [Abstract] Operating Expenses Operating Expenses OPERATING INCOME Operating Income (Loss) Interest expense INCOME (LOSS) BEFORE INCOME TAX (EXPENSE) BENEFIT Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income tax (expense) benefit NET INCOME (LOSS) EARNINGS (LOSS) PER COMMON SHARE: WEIGHTED AVERAGE NUMBER OF COMMON SHARES OUTSTANDING - basic and diluted (in shares) Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Reclassification Adjustment Restatement Adjustment [Member] JBG Companies JBG Companies [Member] JBG Companies [Member] Equity Interest Type [Axis] Equity Interest Type [Axis] Equity Interest Issued or Issuable, Type [Domain] Equity Interest Issued or Issuable, Type [Domain] Wholly Owned Properties Wholly Owned Properties [Member] Real Estate, Type of Property [Axis] Real Estate, Type of Property [Axis] Real Estate [Domain] Real Estate [Domain] Office Building Office Building [Member] Multifamily Multifamily [Member] Other Property Other Property [Member] Asset under Construction Asset under Construction [Member] Future Development Future Development [Member] Future Development [Member] Number of real estate properties Area of real estate property (in square feet) Area of Real Estate Property Number of building units Number of Units in Real Estate Property Summary of Debt Schedule of Long-term Debt Instruments [Table Text Block] Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Affiliate Affiliated Entity [Member] Trustee Director [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Allocations of centralized corporate costs Allocations Of Centralized Corporate Costs [Member] Allocations Of Centralized Corporate Costs [Member] Financing transactions Financing Transactions [Member] Financing Transactions [Member] Supervise cleaning, engineering and security services Supervisory Services of Properties [Member] Supervisory Services of Properties Separation and Combination transaction Separation And Combination Transaction [Member] Separation And Combination Transaction [Member] Consulting agreement Consulting Agreement [Member] Consulting Agreement [Member] Fees from Legacy JBG Funds Fees from Legacy JBG Funds [Member] Fees from Legacy JBG Funds [Member] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Vornado Vornado Realty Trust [Member] Vornado Realty Trust [Member] BMS BMS [Member] BMS [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Financing of the Universal Buildings Financing Of The Universal Buildings [Member] Financing Of The Universal Buildings [Member] Note agreement for development of Bartlett Note Agreement For Development Of Bartlett [Member] Note Agreement For Development Of Bartlett [Member] Mortgage loan secured by Bowen Building Mortgage loan secured by Bowen Building [Member] Mortgage loan secured by Bowen Building [Member] Vornado's revolving credit facility Name of Property [Axis] Name of Property [Axis] Name of Property [Domain] Name of Property [Domain] Universal Buildings, Washington DC Universal Buildings, Washington DC [Member] Universal Buildings, Washington DC [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Allocated amounts included in general and administrative expense Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party Expenses from related parties Related Party Transaction, Expenses from Transactions with Related Party Revenue from related parties Revenue from Related Parties Debt instrument, face amount Debt Instrument, Face Amount Loan to Vornado Origination of Notes Receivable from Related Parties Mortgage loan interest rate Interest Income on loan receivable from Vornado Interest Income, Related Party Accrued interest on mortgage loan Debt Instrument, Increase, Accrued Interest Interest expense to Vornado Interest Expense, Related Party Transaction services, initial period (in months) Related Party Transaction, Initial Potential Service Period Related Party Transaction, Initial Potential Service Period Proceeds from credit facility Related party transaction amount Related Party Transaction, Amounts of Transaction Related party transaction, monthly amount Related Party Transaction, Monthly Transaction Amount Related Party Transaction, Monthly Transaction Amount Liability incurred in connection with the Combination Business Combination, Consideration Transferred, Liabilities Incurred Real estate service revenue Real Estate Revenue, Net Statement of Stockholders' Equity [Abstract] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Shares Common Stock [Member] Additional Paid-In Capital Additional Paid-in Capital [Member] Accumulated Deficit Retained Earnings [Member] Accumulated Other Comprehensive Income AOCI Including Portion Attributable to Noncontrolling Interest [Member] Former Parent Equity Former Parent Equity [Member] Former Parent Equity [Member] Noncontrolling Interests Noncontrolling Interest [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance at beginning of period Balance at beginning of period (in shares) Net loss attributable to common shareholders Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest Deferred compensation shares and options, net Stock Issued During Period, Value, Employee Benefit Plan Contributions from former parent, net Stockholders' Equity Note, Spinoff Transaction Distributions to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Redeemable noncontrolling interest redemption value adjustment and other comprehensive income allocation Noncontrolling Interest, Change in Redemption Value Other comprehensive income Other Balance at end of period (in shares) Balance at end of period Transactions with Vornado and Related Parties Related Party Transactions Disclosure [Text Block] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Assets, Net Other Assets [Member] Other Liabilities, Net Other Liabilities [Member] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest rate swap and caps Interest Rate Swap [Member] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Recurring Fair Value, Measurements, Recurring [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Classified as assets in Other assets, net Derivative Asset Classified as liabilities in Other liabilities, net Derivative Liability Schedule of Earnings (Loss) Per Share, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Antidilutive Securities Excluded from Computation of Earnings (Loss) Per Share Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Business Combinations [Abstract] Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Total revenue Business Acquisition, Pro Forma Revenue Net loss attributable to common shareholders Business Acquisition, Pro Forma Net Income (Loss) Business Acquisition, Pro Forma Earnings Per Share, Diluted Business Acquisition, Pro Forma Earnings Per Share, Diluted Business Acquisition, Pro Forma Earnings Per Share, Basic Business Acquisition, Pro Forma Earnings Per Share, Basic Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual Net unrealized gain on derivative designated as cash flow hedge Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Loss expected to be reclassified into interest expense within the next 12 months Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months Net unrealized gain on derivative not designated as cash flow hedge Combined balance sheet information: Equity Method Investment, Summarized Financial Information, Liabilities and Equity [Abstract] Real estate, net Equity Method Investment, Summarized Financial Information, Assets, Real Estate Investment Property, Net Equity Method Investment, Summarized Financial Information, Assets, Real Estate Investment Property, Net Other assets, net Equity Method Investment, Summarized Financial Information, Assets, Other Equity Method Investment, Summarized Financial Information, Assets, Other Total assets Equity Method Investment, Summarized Financial Information, Assets Mortgages payable, net Equity Method Investment, Summarized Financial Information, Liabilities, Secured Debt Equity Method Investment, Summarized Financial Information, Liabilities, Secured Debt Other liabilities, net Equity Method Investment, Summarized Financial Information, Liabilities, Other Equity Method Investment, Summarized Financial Information, Liabilities, Other Total liabilities Equity Method Investment, Summarized Financial Information, Liabilities Total equity Equity Method Investment, Summarized Financial Information, Equity Excluding Noncontrolling Interests Total liabilities and equity Equity Method Investment, Summarized Financial Information, Liabilities and Equity Combined income statement information: Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) [Abstract] Total revenue Equity Method Investment, Summarized Financial Information, Revenue Operating income Equity Method Investment, Summarized Financial Information, Operating Income (Loss) Equity Method Investment, Summarized Financial Information, Operating Income (Loss) Net income (loss) Equity Method Investment, Summarized Financial Information, Net Income (Loss) Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Debt Instrument [Line Items] Debt Instrument [Line Items] Variable interest rate Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate Fixed interest rate Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate Variable rate amount Long-term Debt, Percentage Bearing Variable Interest, Amount Fixed rate amount Long-term Debt, Percentage Bearing Fixed Interest, Amount Debt, gross Unamortized deferred financing costs and premium/discount, net Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Debt, net