Long-Term Debt - Interest Expense and Capitalized Interest (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Interest expense	$ 40,024	$ 33,064	$ 44,484
Interest income	(2,068)	(4,786)	(1,167)
Capitalized interest	(11,042)	(10,419)	(10,419)
Net interest expense	$ 26,914	$ 17,859	32,898
Energy Resource Technology GOM, Inc [Member]
Debt Instrument [Line Items]
Interest expense			$ 2,800