Fair Value Measurement (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
8.25% Senior subordinated notes due 2016
Fair value and carrying value of debt instruments
Interest rate on debt instrument (as a percent)	8.25%	8.25%
10.25% Senior notes due 2014, net of unamortized discount of $6,564 and $11,035, respectively
Fair value and carrying value of debt instruments
Interest rate on debt instrument (as a percent)	10.25%	10.25%
Unamortized discount	6,564	11,035
6.75% Senior notes due 2020
Fair value and carrying value of debt instruments
Interest rate on debt instrument (as a percent)	6.75%	6.75%
Carrying Amount
Fair value and carrying value of debt instruments
Debt Instrument, Fair Value Disclosure	1,381,000	1,114,000
Carrying Amount | Line of Credit
Fair value and carrying value of debt instruments
Debt Instrument, Fair Value Disclosure	0
Carrying Amount | Senior secured revolving credit facility
Fair value and carrying value of debt instruments
Debt Instrument, Fair Value Disclosure	531,500	170,000
Carrying Amount | 8.25% Senior subordinated notes due 2016
Fair value and carrying value of debt instruments
Debt Instrument, Fair Value Disclosure	200,000	200,000
Carrying Amount | 10.25% Senior notes due 2014, net of unamortized discount of $6,564 and $11,035, respectively
Fair value and carrying value of debt instruments
Debt Instrument, Fair Value Disclosure	348,692	439,000
Carrying Amount | 6.75% Senior notes due 2020
Fair value and carrying value of debt instruments
Debt Instrument, Fair Value Disclosure	300,000	300,000
Estimated Fair Value
Fair value and carrying value of debt instruments
Debt Instrument, Fair Value Disclosure	1,445,000	1,206,000
Estimated Fair Value | Senior secured revolving credit facility
Fair value and carrying value of debt instruments
Debt Instrument, Fair Value Disclosure		170,000
Estimated Fair Value | 8.25% Senior subordinated notes due 2016
Fair value and carrying value of debt instruments
Debt Instrument, Fair Value Disclosure	209,000	210,000
Estimated Fair Value | 10.25% Senior notes due 2014, net of unamortized discount of $6,564 and $11,035, respectively
Fair value and carrying value of debt instruments
Debt Instrument, Fair Value Disclosure	402,000	518,000
Estimated Fair Value | 6.75% Senior notes due 2020
Fair value and carrying value of debt instruments
Debt Instrument, Fair Value Disclosure	302,000	303,000