Equity Investments (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Equity investments in unconsolidated affiliates	$ 186,423,000		$ 186,423,000		$ 187,031,000
Equity in earnings of investments	4,906,000	6,221,000	16,443,000	12,932,000
Payments of distributions to affiliates			3,437,000	9,876,000
Deepwater Gateway, L.L.C. [Member]
Equity method investment, ownership percentage	50.00%		50.00%
Equity investments in unconsolidated affiliates	96,800,000		96,800,000		99,800,000
Capitalized interest	1,400,000		1,400,000		1,500,000
Equity in earnings of investments	600,000	1,300,000	2,700,000	3,600,000
Payments of distributions to affiliates	2,200,000		5,700,000
Independence Hub, LLC [Member]
Equity method investment, ownership percentage	20.00%		20.00%
Equity investments in unconsolidated affiliates	80,200,000		80,200,000		82,400,000
Capitalized interest	5,000,000		5,000,000		5,200,000
Equity in earnings of investments	4,000,000	4,200,000	12,300,000	14,100,000
Payments of distributions to affiliates	4,600,000		14,200,000
Clough Helix JV [Member]
Equity method investment, ownership percentage	50.00%		50.00%
Equity investments in unconsolidated affiliates	9,400,000		9,400,000		4,900,000
Equity in earnings of investments	$ 300,000	$ 700,000	$ 1,400,000	$ (5,000,000)