Investments in Unconsolidated Affiliates - Investments by Investee (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 49,607	$ 51,820	$ 58,736
Medusa Spar LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	49,480	51,820	57,388
Other [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 127	$ 0	$ 1,348