Senior Notes (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 11, 2014
Debt Instrument [Line Items]
Carrying Value		$ 491,160	$ 489,715
Gains Losses On Extinguishment Of Debt
Loss on debt extinguishment		0	(21,538)	$ 0
Premium on early retirement of debt		0	13,837	0
Write-off of deferred financing costs and original issue discount		0	(7,338)	0
Other		0	364	$ 0
Senior Notes
Debt Instrument [Line Items]
Principal		500,000	500,000
Unamortized discount and debt issuance costs		8,840	10,284
Carrying Value		491,160	489,715
Fair Value		$ 212,500	504,500
Percentage of principal amount at which notes may be required to be repurchased in event of change of control		101.00%
Gains Losses On Extinguishment Of Debt
Loss on debt extinguishment	$ (19,300)
Premium on early retirement of debt	13,800
Write-off of deferred financing costs and original issue discount	(5,100)
Other	$ 400
Debt issuance costs incurred in connection with the issuance of the 2019 Notes and 2024 Notes		$ 12,000
Aggregate future maturities of long-term debt
2019		300,000
2024		200,000
Less unamortized discount		(7,573)
Less unamortized debt issuance costs		(1,267)
2017 notes | Senior Notes
Debt Instrument [Line Items]
Interest rate (as a percent)					8.25%
2019 notes | Senior Notes
Debt Instrument [Line Items]
Principal		300,000	300,000
Unamortized discount and debt issuance costs		4,785	5,741
Carrying Value		295,214	294,259
Fair Value		$ 151,500	$ 315,000
Interest rate (as a percent)		8.50%	8.50%
2024 notes | Senior Notes
Debt Instrument [Line Items]
Principal		$ 200,000	$ 200,000		$ 200,000
Unamortized discount and debt issuance costs		4,055	4,543
Carrying Value		195,945	195,457
Fair Value		$ 61,000	$ 189,500
Interest rate (as a percent)		6.375%	6.375%		6.375%
Issue price as a percent of the face amount					100.00%