Selected Balance Sheet Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2003
Schedule of Equity Method Investments [Line Items]
Deferred income taxes	$ 61,589,000	$ 22,604,000
Equity Method Investment, Significant Property, Plant and Equipment Owned by Equity Method Investee	75.00%
Equity Method Investments	37,462,000	42,619,000
Equity Method Investment, Percentage of Cumulative Undistributed Earnings	50.00%
Medusa Spar LLC Investment [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of equity method investment	50.00%
Equity Method Investment, Aggregate Cost				43,700,000
Equity Method Investment, Significant Property, Plant and Equipment Owned by Equity Method Investee	75.00%
Equity Method Investments	37,376,000	42,540,000
Retained Earnings, Undistributed Earnings from Equity Method Investees	(4,300,000)	900,000
Equity Method Investment, Dividends or Distributions	$ 5,300,000	$ 8,700,000	$ 6,300,000