Equity Investments (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Equity investments in unconsolidated affiliates	$ 173,440,000		$ 175,656,000
Capitalized interest	1,400,000		1,400,000
Equity in earnings of investments	407,000	5,650,000
Payments of distributions to affiliates	5,943,000	480,000
Deepwater Gateway, L.L.C. [Member]
Equity method investment, ownership percentage	50.00%
Equity investments in unconsolidated affiliates	95,100,000		96,000,000
Payments of distributions to affiliates	2,200,000
Independence Hub, LLC [Member]
Equity method investment, ownership percentage	20.00%
Equity investments in unconsolidated affiliates	78,300,000		79,700,000
Capitalized interest	4,800,000		4,900,000
Payments of distributions to affiliates	4,200,000
Clough Helix JV [Member]
Equity in earnings of investments	(3,800,000)
Exit Fee	$ 3,000,000