Equity Components [Axis] Common Stock [Member] Paid-in Additional Capital [Member] Accumulated Deficit [Member] Accumulated Other Comprehensive Loss [Member] Award Date [Axis] 2020 [Member] 2021 [Member] Product and Service [Axis] Time and Bareboat Charter Revenues [Member] Voyage Charter Revenues [Member] Contracts of Affreightment Revenues [Member] Antidilutive Securities [Axis] Class A Restricted Stock Units [Member] Class A Stock Options Outstanding [Member] Legal Entity [Axis] Alaska Tanker Company, LLC [Member] Class of Stock [Axis] Class A Common Stock [Member] Award Type [Axis] Restricted Stock Units (RSUs) [Member] Items Not Yet Recognized as a Component of Net Periodic Benefit Cost (Pension and Other Postretirement Plans) [Member] Time Charter Revenue [Member] Fair Value Hierarchy and NAV [Axis] Level 1 [Member] Debt Instrument [Axis] Unsecured Senior Notes [Member] Level 2 [Member] Term Loan Agreement, Due 2023 [Member] Term Loan Agreements, Due 2024 [Member] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Employees, Including Senior Officers [Member] Certain Senior Officers [Member] Scenario [Axis] Decrease Depending on Applicable Measures and Targets [Member] Banc of America Leasing & Capital, LLC [Member] Class A Warrants [Member] Short-term Time Charter Contracts [Member] Alaska Tankers Term Loan Agreement, Due 2025 [Member] OSG 204 LLC Term Loan Agreement, Due 2025 [Member] Term Loan Agreement, Due 2026 [Member] Subject to Increase RSU Award [Member] Variable Rate [Axis] LIBOR Plus [Member] Document And Entity Information Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Current Reporting Status Entity Interactive Data Current Entity Filer Category Entity Small Business Flag Entity Emerging Growth Company Entity Shell Company Entity Common Stock, Shares Outstanding Document Fiscal Period Focus Document Fiscal Year Focus Statement of Financial Position [Abstract] ASSETS Current Assets: Cash and cash equivalents Restricted cash Voyage receivables, including unbilled of $6,586 and $5,611, net of reserve for doubtful accounts Income tax receivable Other receivables Inventories, prepaid expenses and other current assets Total Current Assets Vessels and other property, less accumulated depreciation Deferred drydock expenditures, net Total Vessels, Other Property and Deferred Drydock Restricted cash - non current Investments in and advances to affiliated companies Intangible assets, less accumulated amortization Operating lease right-of-use assets Other assets Total Assets LIABILITIES AND EQUITY Current Liabilities: Accounts payable, accrued expenses and other current liabilities Current portion of operating lease liabilities Current portion of finance lease liabilities Current installments of long-term debt Total Current Liabilities Reserve for uncertain tax positions Noncurrent operating lease liabilities Noncurrent finance lease liabilities Long-term debt Deferred income taxes, net Other liabilities Total Liabilities Equity: Common stock - Class A ($0.01 par value; 166,666,666 shares authorized; 85,845,920 and 85,713,610 shares issued and outstanding) Paid-in additional capital Accumulated deficit Stockholders Equity Subtotal Accumulated other comprehensive loss Total Equity Total Liabilities and Equity Unbilled contracts receivable Class A common stock, par value Class A common stock, shares authorized Class A common stock, shares issued Class A common stock, shares outstanding Income Statement [Abstract] Shipping Revenues: Time and bareboat charter revenues Voyage charter revenues Total Shipping revenues Operating Expenses: Voyage expenses Vessel expenses Charter hire expenses Depreciation and amortization General and administrative Loss on disposal of vessels and other property, including impairments, net Total operating expenses Income from vessel operations Gain on termination of pre-existing arrangement Operating income Other income, net Income before interest expense and income taxes Interest expense Income before income taxes Income tax expense Net income Weighted Average Number of Common Shares Outstanding: Basic - Class A Diluted - Class A Per Share Amounts: Basic and diluted net income - Class A Net income Other comprehensive income, net of tax: Defined benefit pension and other postretirement benefit plans: Net change in unrecognized prior service costs Net change in unrecognized actuarial losses Other comprehensive income Comprehensive income Statement of Cash Flows [Abstract] Cash Flows from Operating Activities: Items included in net income not affecting cash flows: Gain on termination of pre-existing arrangement Amortization of debt discount and other deferred financing costs Compensation relating to restricted stock awards and stock option grants Deferred income tax benefit Interest on finance lease liabilities Non-cash operating lease expense Other - net Distributed earnings of affiliated companies Payments for drydocking Operating lease liabilities Changes in operating assets and liabilities, net Net cash provided by operating activities Cash Flows from Investing Activities: Acquisition, net of cash acquired Expenditures for vessels and vessel improvements Expenditures for other property Net cash used in investing activities Cash Flows from Financing Activities: Payments on debt Tax withholding on share-based awards Issuance of debt, net of issuance and deferred financing costs Payments on principal portion of finance lease liabilities Net cash provided by/(used in) financing activities Net increase/(decrease) in cash, cash equivalents and restricted cash Cash, cash equivalents and restricted cash at beginning of period Cash, cash equivalents and restricted cash at end of period Statement [Table] Statement [Line Items] Beginning balance Other comprehensive income Forfeitures, cancellations, issuance and vesting of restricted stock awards, net Compensation related to Class A options granted and restricted stock awards Ending balance Statement of Stockholders' Equity [Abstract] Class A warrants outstanding Organization, Consolidation and Presentation of Financial Statements [Abstract] Basis of Presentation Accounting Policies [Abstract] Recently Adopted and Issued Accounting Standards Revenue from Contract with Customer [Abstract] Revenue Recognition Earnings Per Share [Abstract] Earnings per Common Share Fair Value Disclosures [Abstract] Fair Value Measurements and Fair Value Disclosures Income Tax Disclosure [Abstract] Taxes Investments, All Other Investments [Abstract] Investment in Alaska Tanker Company, LLC Share-based Payment Arrangement [Abstract] Capital Stock and Stock Compensation Equity [Abstract] Accumulated Other Comprehensive Loss Leases [Abstract] Leases Property, Plant and Equipment [Abstract] Vessels Debt Disclosure [Abstract] Debt Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Recently Adopted Accounting Standards Recently Issued Accounting Standards Schedule of Disaggregation of Revenue Schedule of Earnings Per Share Schedule of Hierarchy Categorized on Fair Value Accumulated Other Comprehensive Loss Schedule of Components of Accumulated Other Comprehensive Loss Schedule of Changes in Balances of Component of Accumulated Other Comprehensive Loss Period for voyage completion Number of products participating in U.S Maritime Security Program Deferred Revenue Contract balances from contracts with customers Revenue remaining performance obligations Total shipping revenues Warrant exercise price Antidilutive securities excluded from computation of earnings per share, amount Dilutive equity awards outstanding Weighted average common shares outstanding: Class A common stock - basic Weighted average common shares outstanding: Class A common stock - diluted Cash Total assets Term loan agreements, fair value Liabilities Restricted cash, fair value disclosure Restricted cash Income tax provisions Change in the state tax rate Operating loss carryforwards, expiration date Investment interest rate Contract term ending date Payment to purchase of oil carrier vessels Acquisition by borrowing Acquired term loan Purchase of vessels term description Business combination consideration, amount Title of Individual [Axis] Shares repurchased during period Stock repurchased during period, per share amount Common stock shares issued Number of warrants exercised Share based payment options grants in period gross Share based payment options granted, per share Items not yet recognized as a component of net periodic benefit cost (pension and other postretirement benefit plans) Current period change, excluding amounts reclassified from accumulated other comprehensive income Amounts reclassified from accumulated other comprehensive income Total change in accumulated other comprehensive income Statistical Measurement [Axis] Long-Lived Tangible Asset [Axis] Income Statement Location [Axis] Operating right-of-use assets Operating right-of-use liabilities Future minimum commitments, remainder of 2020 Future minimum commitments, 2021 Future minimum commitments, 2022 Future minimum commitments, 2023 Lease income Straight-line adjustments Debt instrument, face amount Payments of loan Debt, weighted average interest rate Construction loan Debt instrument description Annual principal payment loan for 2020 Annual principal payment loan for 2021 Annual principal payment loan for 2022 Annual principal payment loan for 2023 Annual principal payment loan for 2024 Annual principal payment loan for thereafter Debt instrument, interest rate, stated percentage Debt instrument, term Debt instrument, due Number Of Products Participating In U.S Maritime Security Program (MSP) Revenue From Contract With Customer, Performance Obligation Period Stock repurchased during period, per share amount. AMO and MEBA Pension Plan [Member] AMO Pension Plan [Member] ATBs [Member] Adjustments Due to ASC 606 [Member] Alaska Tanker Company, LLC [Member] ABR [Member] Articulated Tug Barge [Member] Banc of America Leasing & Capital, LLC [Member] Benefit Obligations [Member] Board of Directors [Member] Certain Senior Officers [Member] Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line. Class A Restricted Stock Units [Member] Class A Stock Options Outstanding [Member] Class A Warrant [Member] Class A Warrants [Member] Contracts of Affreightment [Member] Contracts of Affreightment Revenues [Member] Customer One [Member] Customer Three [Member] Customer Two [Member] Decrease Depending on Applicable Measures and Targets [Member] Deferred drydock expenditures, net. Depreciation [Member] Disposals [Member] Disposals [Member] Election 1 Notes [Member] Election 2 Notes [Member] Employees, Including Senior Officers [Member] Expected to be Recognized [Member] Expected to be recognized During 2020 [Member] Green Zone Status Plan [Member] Gunderson Marine LLC [Member] Incentive Plans [Member] Income before interest expense and income taxes. Changes in operating lease liabilities. Intermediate Term Bond Fund [Member] International Growth [Member] International Value [Member] MEBA Pension Plan [Member] Mandatory Prepayment [Member] Maritrans Plan [Member] Monroe Energy LLC [Member] Net Periodic Benefit Cost [Member] Net Periodic Benefit Costs, Seagoing Employees [Member] Net Periodic Benefit Costs, Shore-based Employees [Member] Recently issued accounting standards [Policy Text Block] Non-employee Directors [Member] Non-cash operating lease expense. 8.125% Notes [Member] Notes Payable 1 [Member] Notes Payable 2 [Member] OBS Facilities [Member] OBS Term Loan [Member] OSG Bulk Ships, Inc and OBS Subsidiaries [Member] Office Space [Member] Office Space Rental [Member] Operating loss carryforwards, expiration date. Optional Prepayment [Member] Unrealized Losses on Cash Flow Hedges [Member] Other comprehensive income (loss) including capital adjustments related to spinoff net of tax. Other Income Expense Net [Member] Overseas Gulf Coast and Overseas Sun Coast [Member] Payments for drydocking. Petrobras America Inc [Member] Total vessels and other property. Restricted cash, fair value disclosure. SIU-Tanker Agreement and SIU-Tug Agreement [Member] Sale of Two ATB's [Member] Schedule of Changes in Balances of Component of Accumulated Other Comprehensive Loss [Table Text Block] SeaRiver Maritime Inc [Member] Seafarers Pension Plan [Member] Senior Officers [Member] Shell [Member] Short-term Time Charter Contracts [Member] Small Company - Mid Growth [Member] Small Company - Mid Value [Member] Small Company Mid Value Prefeered Stock [Member] Stock issued during period value restricted stock award issued and vested, net of forfeitures. Stockholders equity subtotal. Subject to Increase RSU Award [Member] Term Loan Agreement 1 [Member] Term Loan Agreement 3 [Member] Term Loan Agreement 2 [Member] Term Loan Credit Agreement [Member] Term Loan One [Member] Term Loan Three [Member] Term Loan Two [Member] Term Loan 2026 [Member] Term Loan 2023 [Member] Three and Two Individual Customers [Member] Time and Bareboat Charter Revenues [Member] Time Charter Revenue [Member] Transfers from construction in progress [Member] Two Barges [Member] 2019 [Member] 2020 [Member] 2021 [Member] U.S. Maritime Security Program [Member] Unsecured Senior Notes [Member] Vessel expenses. Vessels Chartered-In [Member] Vessels, deferred drydock and other property, non-current. Vessels [Member] Voyage Charter Revenues [Member] Voyage expenses. Wintrust Commercial Finance [Member] Yellow Zone Status Plan [Member] Inventories, prepaid expenses and other current assets. Term Loan Agreement, Due 2023 [Member] Term Loan Agreements, Due 2024 [Member] Alaska Tankers Term Loan Agreement, Due 2025 [Member] OSG 204 LLC Term Loan Agreement, Due 2025 [Member] Term Loan Agreement, Due 2026 [Member] Acquisition by borrowing. Income from vessel operations. Gain on termination of pre-existing arrangement. Operating right-of-use liabilities. Contract term ending date. Purchase of vessels term description. Assets, Current VesselsDeferredDrydockAndOtherPropertyNonCurrent Assets Liabilities, Current Liabilities [Default Label] StockholdersEquitySubtotal Stockholders' Equity Attributable to Parent Liabilities and Equity Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Operating Expenses Operating Income (Loss) IncomeBeforeInterestExpenseAndIncomeTaxes Interest Expense Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax Comprehensive Income (Loss), Net of Tax, Attributable to Parent Income (Loss) from Equity Method Investments, Net of Dividends or Distributions PaymentsForDrydocking Net Cash Provided by (Used in) Operating Activities Payments to Acquire Businesses, Net of Cash Acquired Payments to Acquire Other Property, Plant, and Equipment Net Cash Provided by (Used in) Investing Activities Payments of Debt Issuance Costs Payment, Tax Withholding, Share-based Payment Arrangement Finance Lease, Principal Payments Net Cash Provided by (Used in) Financing Activities Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations Restricted Cash