Investments in Unconsolidated Affiliates - Investments by Investee (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 46,639	$ 49,607	$ 49,607
Medusa Spar LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	46,507		49,480
Other [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 132		$ 127