Fair Value Measurement (Details 3) (USD $)			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Senior secured revolving credit facility	Dec. 31, 2011 Senior secured revolving credit facility	Dec. 31, 2012 8.25% Senior subordinated notes due 2016	Dec. 31, 2012 10.25% Senior notes due 2014	Dec. 31, 2011 10.25% Senior notes due 2014	May 27, 2009 10.25% Senior notes due 2014	Dec. 31, 2012 6.75% Senior notes due 2020	Dec. 31, 2012 Senior Notes 6.375% Due 2022	Dec. 31, 2012 Carrying Amount	Dec. 31, 2011 Carrying Amount	Dec. 31, 2012 Carrying Amount Senior secured revolving credit facility	Dec. 31, 2011 Carrying Amount Senior secured revolving credit facility		Dec. 31, 2011 Carrying Amount 8.25% Senior subordinated notes due 2016	Dec. 31, 2012 Carrying Amount 10.25% Senior notes due 2014		Dec. 31, 2011 Carrying Amount 10.25% Senior notes due 2014		Dec. 31, 2012 Carrying Amount 6.75% Senior notes due 2020	Dec. 31, 2011 Carrying Amount 6.75% Senior notes due 2020	Dec. 31, 2012 Carrying Amount Senior Notes 6.375% Due 2022	Dec. 31, 2012 Estimated Fair Value	Dec. 31, 2011 Estimated Fair Value	Dec. 31, 2012 Estimated Fair Value Senior secured revolving credit facility		Dec. 31, 2011 Estimated Fair Value Senior secured revolving credit facility		Dec. 31, 2011 Estimated Fair Value 8.25% Senior subordinated notes due 2016	Dec. 31, 2012 Estimated Fair Value 10.25% Senior notes due 2014	Dec. 31, 2011 Estimated Fair Value 10.25% Senior notes due 2014	Dec. 31, 2012 Estimated Fair Value 6.75% Senior notes due 2020	Dec. 31, 2011 Estimated Fair Value 6.75% Senior notes due 2020	Dec. 31, 2012 Estimated Fair Value Senior Notes 6.375% Due 2022	Dec. 31, 2012 Cash and Cash Equivalents Carrying Amount	Dec. 31, 2012 Cash and Cash Equivalents Estimated Fair Value	Dec. 31, 2012 Fair Value, Inputs, Level 2	Dec. 31, 2012 Fair Value, Inputs, Level 2 Estimated Fair Value Senior secured revolving credit facility		Dec. 31, 2012 Fair Value, Inputs, Level 1	Dec. 31, 2012 Fair Value, Inputs, Level 1 Estimated Fair Value 10.25% Senior notes due 2014		Dec. 31, 2012 Fair Value, Inputs, Level 1 Estimated Fair Value 6.75% Senior notes due 2020	Dec. 31, 2012 Fair Value, Inputs, Level 1 Estimated Fair Value Senior Notes 6.375% Due 2022	Dec. 31, 2012 Fair Value, Inputs, Level 1 Cash and Cash Equivalents Estimated Fair Value
Fair value and carrying value of debt instruments
Interest Rate Generally Fixed, Number of Days			30 days	30 days
Cash and Cash Equivalents, Fair Value Disclosure																																				$ 0	$ 0									$ 0
Debt Instrument, Fair Value Disclosure											1,668,000,000	1,387,000,000	563,000,000	532,000,000	[1]	200,000,000	205,000,000	[2]	355,000,000	[3]	300,000,000	300,000,000	600,000,000	1,742,000,000	1,445,000,000	563,000,000	[1]	532,000,000	[1]	209,000,000	229,000,000	402,000,000	323,000,000	302,000,000	627,000,000			563,000,000	563,000,000	[1]	1,179,000,000	229,000,000	[3]	323,000,000	627,000,000
Senior secured revolving credit facility	562,900,000	531,500,000
Interest rate on debt instrument (as a percent)					8.25%	10.25%			6.75%	6.375%
Unamortized discount						$ 2,340,000	$ 6,564,000	$ 21,000,000

[1] (1)The Company's credit facility can be repaid at any time without penalty. Interest is generally fixed for 30-day increments at the prime rate or LIBOR plus a stipulated margin for the amount utilized and at a stipulated percentage as a commitment fee for the portion not utilized. The carrying amount of the credit facility approximated fair value due to the short-term maturities of the borrowings and because the borrowings bear interest at variable market rates.

[2] (2)Carrying amount does not include unamortized discount of $2.3 million.

[3] (2)Carrying amount does not include unamortized discount of $6.6 million.