Investments in Unconsolidated Affiliates - Investments by Investee (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 42,619	$ 49,607
Medusa Spar LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	42,540	49,480
Other [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 79	$ 127