Equity Investments - Narrative (Details) ft in Thousands	1 Months Ended				12 Months Ended
	Feb. 29, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Dec. 31, 2004 USD ($)	Dec. 31, 2015 USD ($) ft	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated affiliates		$ 26,200,000			$ 26,200,000	$ 149,623,000
Loss from equity method investments					124,345,000	(879,000)	$ (2,965,000)
Amount loss exceeded carrying amount of investment		$ 8,308,000			$ 8,308,000	0
Consideration transferred for business sold			$ 1,500,000,000
Deepwater Gateway, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest		50.00%			50.00%
Equity investments in unconsolidated affiliates		$ 26,200,000			$ 26,200,000	80,900,000
Capitalized interest		1,200,000			1,200,000	1,200,000
Loss from equity method investments					49,400,000
Impairment charge		96,700,000
Estimated fair value		70,800,000			70,800,000
Asset retirement obligation		$ 20,800,000			$ 20,800,000
Deepwater Gateway, LLC [Member] | Subsequent Event [Member]
Schedule of Equity Method Investments [Line Items]
Cash distributions	$ 1,200,000
Sale of ownership interest for cash	$ 25,000,000
Independence Hub, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest		20.00%			20.00%
Equity investments in unconsolidated affiliates						68,800,000
Capitalized interest		$ 3,600,000			$ 3,600,000	$ 3,900,000
Loss from equity method investments					$ 74,900,000
Participation fee				$ 1,000,000
Water depth (in feet) | ft					8
Amount loss exceeded carrying amount of investment		8,300,000			$ 8,300,000
Impairment charge		343,300,000
Estimated fair value		0			0
Asset retirement obligation		42,100,000			42,100,000
Asset retirement obligation, net of remaining working capital		$ 8,300,000			$ 8,300,000