Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		86 Months Ended	89 Months Ended
	Mar. 31, 2013 item	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013
Segment Information
Number of geographic operating segments	2
Segment Information
Operating costs and expense	$ 112,452	$ 37,715		$ 1,052,051
Operating income (loss)	(112,452)	(37,715)		(1,052,051)
Other (income) expense	15,635	(1,184)		3,871
Net income (loss)	(128,087)	(36,531)	(927,835)	(1,055,922)
Additions to Property and Equipment, net	29,957	79,233
U.S. Gulf of Mexico
Segment Information
Operating costs and expense	23,105	24,671
Operating income (loss)	(23,105)	(24,671)
Additions to Property and Equipment, net	54,859	22,346
West Africa
Segment Information
Operating costs and expense	89,347	13,044
Operating income (loss)	(89,347)	(13,044)
Additions to Property and Equipment, net	$ (24,902)	$ 56,887