Equity Investments (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 ft item	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Number of equity investments	2
Equity investments in unconsolidated affiliates	$ 149,623,000	$ 157,919,000
Water depth	8,000
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	80,900,000	85,800,000
Capitalized interest	1,200,000	1,300,000
Independence Hub, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	20.00%
Equity investments in unconsolidated affiliates	68,800,000	72,100,000
Capitalized interest	$ 3,900,000	$ 4,300,000