Investments in Unconsolidated Affiliates - Condensed Statements Of Income (Details) (Medusa Spar LLC Investment [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Medusa Spar LLC Investment [Member]
ASSETS
Cash and cash equivalents	$ 2,904	$ 217	$ 949
Other current assets	5,302	3,189	4,116
Property and Equipment, net	91,073	100,551	110,028
Total Assets	99,279	103,957	115,093
LIABILITIES AND MEMBERS’ EQUITY
Current Liabilities	18	18	17
Members’ Equity	99,261	103,939	115,076
Total Liabilities and Members’ Equity	99,279	103,957	115,093
Condensed Statements of Operations
Revenue	17,536	13,816	16,143
Depreciation	(9,478)	(9,478)	(9,478)
General and administrative	(72)	(71)	(70)
Net Income	$ 7,986	$ 4,267	$ 6,595