BASIS OF PRESENTATION AND DESCRIPTION OF BUSINESS	12 Months Ended
Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	BASIS OF PRESENTATION AND DESCRIPTION OF BUSINESS The consolidated financial statements include the accounts of Overseas Shipholding Group, Inc., a Delaware corporation incorporated in 1969, and its wholly owned subsidiaries (the “Company” or “OSG”, or “we” or “us” or “our”). All significant intercompany balances and transactions have been eliminated in consolidation. Investments in 50% or less owned affiliated companies, in which the Company exercises significant influence, are accounted for by the equity method. Dollar amounts, except per share amounts, are in thousands. Certain prior period amounts have been reclassified in the Consolidated Statements of Cash Flows to conform to the current period presentation. The reclassifications in the Consolidated Statements of Cash Flows had no impact on net cash provided by operating activities and net cash provided by/(used in) investing and financing activities. The Company owns and operates a fleet of oceangoing vessels engaged primarily in the transportation of crude oil and refined petroleum products in the U.S. Flag trade through its wholly owned subsidiary, OSG Bulk Ships, Inc. (“OBS”), a New York corporation. On November 30, 2016 (the “Distribution Date”), OSG completed the separation of its business into two independent publicly-traded companies through the spin-off of its then wholly-owned subsidiary International Seaways, Inc. (“INSW”). The spin-off separated OSG and INSW into two distinct businesses with separate management. OSG retained the U.S. Flag business and relocated its headquarters to Tampa, Florida. The spin-off transaction was in the form of a pro rata distribution of INSW’s common stock to our stockholders and warrant holders of record as of 5:00 p.m., New York time on November 18, 2016 (the “Record Date”). On the Distribution Date, each holder of OSG common stock received 0.3333 shares of INSW’s common stock for every share of OSG common stock held on the Record Date. Each holder of OSG warrants received 0.3333 shares of INSW’s common stock for every one share of OSG common stock they would have received if they exercised their warrants immediately prior to the Distribution (or 0.063327 INSW shares per warrant). The spin-off was completed pursuant to a Separation and Distribution Agreement and several other agreements with INSW related to the spin-off. These agreements governed the relationship between and INSW and OSG following the spin-off and provided for the allocation of various assets, liabilities, rights and obligations. These agreements also included a Transition Services Agreement and an Employee Matters Agreement, which expired during 2017, covering arrangements for transition services to be provided by OSG to INSW and by INSW to OSG. See Note 5, "Discontinued Operations, " for additional information. In accordance with Accounting Standards Update (“ASU”) 2014-8, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, the assets and liabilities and results of operations of INSW are reported as discontinued operations, net of taxes, for all periods presented. Accordingly, all references made to financial data in this Annual Report on Form 10-K are to the Company’s continuing operations unless specifically noted. See Note 5, “Discontinued Operations,” for additional information. As further discussed in Note 14, “Capital Stock and Stock Compensation,” the Company’s board of directors (the “Board”) approved a stock dividend of Class A common stock, whereby on December 17, 2015, all stockholders of record of the Company’s Class A and B common stock as of December 3, 2015 (the “record date”), received a dividend of one-tenth of one share of Class A common stock for each share of Class A common stock and Class B common stock held by them as of the record date. In addition, as discussed further in Note 14, effective May 27, 2016, all Class B common shares and Class B warrants automatically converted into one Class A common share and one Class A warrant, respectively, and on June 2, 2016 the Board approved an amendment (the "Reverse Split Amendment") to the Company's Amended and Restated Certificate of Incorporation. The Reverse Split Amendment effected a one (1) for six (6) reverse stock split and corresponding reduction of the number of authorized shares of common stock, par value $0.01 per share (the "Reverse Split"). The Reverse Split Amendment became effective on June 13, 2016. In accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) ASC 260, Earnings Per Share, the Company adjusted the computations of basic and diluted earnings per share retroactively for all periods presented to reflect that change in its capital structure. Accordingly, amounts previously reported in 2015 with respect to earnings per share, outstanding Class A shares, Class A restricted stock units, restricted shares and stock options have been restated where appropriate. See Note 4, “Earnings per Common Share,” for additional information.

BASIS OF PRESENTATION AND DESCRIPTION OF BUSINESS

The consolidated financial statements include the accounts of Overseas Shipholding Group, Inc., a Delaware corporation incorporated in 1969, and its wholly owned subsidiaries (the “Company” or “OSG”, or “we” or “us” or “our”). All significant intercompany balances and transactions have been eliminated in consolidation. Investments in 50% or less owned affiliated companies, in which the Company exercises significant influence, are accounted for by the equity method. Dollar amounts, except per share amounts, are in thousands. Certain prior period amounts have been reclassified in the Consolidated Statements of Cash Flows to conform to the current period presentation. The reclassifications in the Consolidated Statements of Cash Flows had no impact on net cash provided by operating activities and net cash provided by/(used in) investing and financing activities.

The Company owns and operates a fleet of oceangoing vessels engaged primarily in the transportation of crude oil and refined petroleum products in the U.S. Flag trade through its wholly owned subsidiary, OSG Bulk Ships, Inc. (“OBS”), a New York corporation.

On November 30, 2016 (the “Distribution Date”), OSG completed the separation of its business into two independent publicly-traded companies through the spin-off of its then wholly-owned subsidiary International Seaways, Inc. (“INSW”). The spin-off separated OSG and INSW into two distinct businesses with separate management. OSG retained the U.S. Flag business and relocated its headquarters to Tampa, Florida.

The spin-off transaction was in the form of a pro rata distribution of INSW’s common stock to our stockholders and warrant holders of record as of 5:00 p.m., New York time on November 18, 2016 (the “Record Date”). On the Distribution Date, each holder of OSG common stock received 0.3333 shares of INSW’s common stock for every share of OSG common stock held on the Record Date. Each holder of OSG warrants received 0.3333 shares of INSW’s common stock for every one share of OSG common stock they would have received if they exercised their warrants immediately prior to the Distribution (or 0.063327 INSW shares per warrant).

The spin-off was completed pursuant to a Separation and Distribution Agreement and several other agreements with INSW related to the spin-off. These agreements governed the relationship between and INSW and OSG following the spin-off and provided for the allocation of various assets, liabilities, rights and obligations. These agreements also included a Transition Services Agreement and an Employee Matters Agreement, which expired during 2017, covering arrangements for transition services to be provided by OSG to INSW and by INSW to OSG. See Note 5, "Discontinued Operations, " for additional information.

In accordance with Accounting Standards Update (“ASU”) 2014-8, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, the assets and liabilities and results of operations of INSW are reported as discontinued operations, net of taxes, for all periods presented. Accordingly, all references made to financial data in this Annual Report on Form 10-K are to the Company’s continuing operations unless specifically noted. See Note 5, “Discontinued Operations,” for additional information.

As further discussed in Note 14, “Capital Stock and Stock Compensation,” the Company’s board of directors (the “Board”) approved a stock dividend of Class A common stock, whereby on December 17, 2015, all stockholders of record of the Company’s Class A and B common stock as of December 3, 2015 (the “record date”), received a dividend of one-tenth of one share of Class A common stock for each share of Class A common stock and Class B common stock held by them as of the record date. In addition, as discussed further in Note 14, effective May 27, 2016, all Class B common shares and Class B warrants automatically converted into one Class A common share and one Class A warrant, respectively, and on June 2, 2016 the Board approved an amendment (the "Reverse Split Amendment") to the Company's Amended and Restated Certificate of Incorporation. The Reverse Split Amendment effected a one (1) for six (6) reverse stock split and corresponding reduction of the number of authorized shares of common stock, par value $0.01 per share (the "Reverse Split"). The Reverse Split Amendment became effective on June 13, 2016. In accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) ASC 260, Earnings Per Share, the Company adjusted the computations of basic and diluted earnings per share retroactively for all periods presented to reflect that change in its capital structure. Accordingly, amounts previously reported in 2015 with respect to earnings per share, outstanding Class A shares, Class A restricted stock units, restricted shares and stock options have been restated where appropriate. See Note 4, “Earnings per Common Share,” for additional information.