Debt - 9.5% Senior Notes due 2018 (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 30, 2014	Sep. 30, 2014	Oct. 19, 2010	Feb. 25, 2011
Debt Instrument [Line Items]
Maximum Amount of Aggregate Principal Redeemed With Net Proceeds Raised in One or More Equity Offerings		35.00%
Comulsory Purchase Price Under Change of Control		101.00%
Compulsory Purchase Price Under Sale of Assets Under Certain Circumstances		100.00%
Minimum Aggregate Principal Amount Required for Trustees or Other Holders to Declare Principal and Accrued Interest Immediately Due	25.00%
Gain (Loss) on Extinguishment of Debt, Deferred Financing Costs	$ 11,900,000
Unamortized Discount	0	19,700,000
Gain (Loss) on Extinguishment of Debt, Unamortized Premium (Discount)	16,900,000
Repayments of Long-term Debt	1,264,086,000	4,800,000	216,037,000
Loss on extinguishment of debt	64,859,000	58,000	5,554,000
Gain (Loss) on Extinguishment of Debt, Make-Whole Premium	36,100,000
Other Assets
Debt Instrument [Line Items]
Deferred Finance Costs, Net		14,000,000
Senior Notes, due Oct 2018, fixed rate 9.5%
Debt Instrument [Line Items]
Debt Instrument, Face Amount						825,000,000
Senior note interest rate		9.50%				9.50%
Percent of Consolidated Net Income Used to Calculated Restricted Payments, Annual Mininum						50.00%
Deferred Finance Costs, Net						28,200,000
Amortization of Financing Costs	2,200,000	2,700,000	2,600,000
Gain (Loss) on Extinguishment of Debt, Deferred Financing Costs			2,300,000
Unamortized Discount						29,600,000
Amortization of Debt Discount (Premium)	2,800,000	3,500,000	3,400,000
Gain (Loss) on Extinguishment of Debt, Unamortized Premium (Discount)			2,700,000
Repayments of Long-term Debt				761,000,000
Gain (Loss) on Extinguishment of Debt, Make-Whole Premium				36,100,000
Amended Senior Secured Revolving Credit Facility
Debt Instrument [Line Items]
Deferred Finance Costs, Net							800,000
Unamortized Discount							7,400,000
Repayments of Long-term Debt					463,600,000
Loss on extinguishment of debt					0
Debt Redemption, After December 2013 and Before October 30, 2014
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage						100.00%
Debt Redemption Premium	36,100,000
Revolving Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Restrictive Covenant, General Restricted Payment Allowance						35,000,000
Percent of Excess Cash Flow Required For Mandatory Prepayment, Annual Mininum						50.00%
Revolving Credit Facility | Maximum
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital						5.75
Revolving Credit Facility | First Trigger
Debt Instrument [Line Items]
Percent of Excess Cash Flow Required For Mandatory Prepayment, Annual Mininum						75.00%
Revolving Credit Facility | First Trigger | Maximum
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital						5.75
Revolving Credit Facility | First Trigger | Minimum
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital						5.25
Revolving Credit Facility | Second Trigger
Debt Instrument [Line Items]
Percent of Excess Cash Flow Required For Mandatory Prepayment, Annual Mininum						100.00%
Revolving Credit Facility | Second Trigger | Minimum
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital						5.25