Equity Investments (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated affiliates	$ 161,200,000		$ 161,200,000		$ 167,599,000
Equity in earnings of investments	857,000	1,392,000	2,150,000	7,547,000
Deepwater Gateway, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	50.00%		50.00%
Equity investments in unconsolidated affiliates	87,500,000		87,500,000		91,400,000
Capitalized interest	1,300,000		1,300,000		1,300,000
Independence Hub, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	20.00%		20.00%
Equity investments in unconsolidated affiliates	73,700,000		73,700,000		76,200,000
Capitalized interest	$ 4,300,000		$ 4,300,000		$ 4,600,000