Equity Investments (Details) ft in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2015 USD ($) equity_investment ft	Dec. 31, 2014 USD ($)
Schedule of Equity Method Investments [Line Items]
Number of equity investments | equity_investment	2
Equity investments in unconsolidated affiliates	$ 145,588	$ 149,623
Deepwater Gateway, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	50.00%
Equity investments in unconsolidated affiliates	$ 78,600	80,900
Capitalized interest	$ 1,200	1,200
Independence Hub, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	20.00%
Equity investments in unconsolidated affiliates	$ 67,000	68,800
Capitalized interest	$ 3,800	$ 3,900
Water depth | ft	8