Schedule I Condensed Financial Information Parent - Accounts, notes, loans and financing receivables (Details) - Parent Company [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net reduction in general and administrative expenses	$ (6,715)	$ (25,159)	$ (28,802)
Osg Bulk Ships Inc [Member]
Net reduction in general and administrative expenses	(6,715)	(17,321)	(11,617)
Osg International Inc [Member]
Net reduction in general and administrative expenses	$ 0	$ (7,838)	$ (17,185)