Long-Term Debt (Convertible Senior Notes Due 2025 and Other) (Details) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 28, 2013	Dec. 31, 2012	Mar. 31, 2012	Mar. 31, 2005
Debt Instrument [Line Items]
Long-term debt, carrying value	$ 572,292,000	$ 592,668,000
Amortization of deferred financing costs	4,870,000	5,187,000	9,086,000
Loss on early extinguishment of debt		12,100,000	17,127,000
Repayment of Helix Term Notes	15,000,000	374,681,000	12,569,000
Amortization of debt discount	5,596,000	5,172,000	9,729,000
Deferred financing costs	3,586,000	10,954,000	7,580,000
Convertible Senior Notes 2025 [Member]
Debt Instrument [Line Items]
Long-term debt, carrying value							300,000,000
Debt instrument interest rate							3.25%
Debt instrument issued percentage							100.00%
Effective interest rate							6.60%
Debt instrument, repurchase amount						142,200,000
Repayments of debt						145,100,000
Interest paid						1,100,000
Payment of debt extinguishment costs						1,800,000
Amortization of deferred financing costs						300,000
Loss on early extinguishment of debt						5,600,000
Repayment of Helix Term Notes				3,500,000	154,300,000
Amortization of debt discount						$ 3,500,000