Fair Value Measurement (Details 3) (USD $)		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012 Senior secured revolving credit facility	Jun. 30, 2012 8.25% Senior subordinated notes due 2016	Jun. 30, 2012 10.25% Senior notes due 2014, net of unamortized discount	Dec. 31, 2011 10.25% Senior notes due 2014, net of unamortized discount	Jun. 30, 2012 6.75% Senior notes due 2020	Jun. 30, 2012 6.375% Senior notes due 2022	Mar. 09, 2012 6.375% Senior notes due 2022	Jun. 30, 2012 Level 1	Jun. 30, 2012 Level 2	Jun. 30, 2012 Carrying Amount	Dec. 31, 2011 Carrying Amount	Jun. 30, 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	Jun. 30, 2012 Carrying Amount 10.25% Senior notes due 2014, net of unamortized discount		Dec. 31, 2011 Carrying Amount 10.25% Senior notes due 2014, net of unamortized discount		Jun. 30, 2012 Carrying Amount 6.75% Senior notes due 2020	Dec. 31, 2011 Carrying Amount 6.75% Senior notes due 2020	Jun. 30, 2012 Carrying Amount 6.375% Senior notes due 2022	Jun. 30, 2012 Carrying Amount Cash and cash equivalents	Dec. 31, 2011 Estimated Fair Value	Jun. 30, 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	Jun. 30, 2012 Estimated Fair Value 10.25% Senior notes due 2014, net of unamortized discount		Dec. 31, 2011 Estimated Fair Value 10.25% Senior notes due 2014, net of unamortized discount		Jun. 30, 2012 Estimated Fair Value 6.75% Senior notes due 2020	Dec. 31, 2011 Estimated Fair Value 6.75% Senior notes due 2020	Jun. 30, 2012 Estimated Fair Value 6.375% Senior notes due 2022	Jun. 30, 2012 Estimated Fair Value Cash and cash equivalents	Jun. 30, 2012 Estimated Fair Value Level 1 10.25% Senior notes due 2014, net of unamortized discount		Jun. 30, 2012 Estimated Fair Value Level 1 6.75% Senior notes due 2020	Jun. 30, 2012 Estimated Fair Value Level 1 6.375% Senior notes due 2022	Jun. 30, 2012 Estimated Fair Value Level 1 Cash and cash equivalents
Fair value and carrying value of financial instruments
Cash and Cash Equivalents, Fair Value Disclosure																									$ 0														$ 0					$ 0
Debt Instrument, Fair Value Disclosure	1,564,000,000								1,163,000,000	401,000,000	1,506,000,000	1,387,000,000	401,000,000	[1]	532,000,000	[1]	200,000,000	205,000,000	[2]	355,000,000	[3]	300,000,000	300,000,000	600,000,000		1,445,000,000	401,000,000	[1]	532,000,000	[1]	209,000,000	228,000,000	[2]	402,000,000	[3]	314,000,000	302,000,000	621,000,000		228,000,000	[2]	314,000,000	621,000,000
Interest rate on debt instrument (as a percent)			8.25%	10.25%		6.75%	6.375%	6.375%
Unamortized discount				$ 3,083,000	$ 6,564,000
Interest Rate Generally Fixed (Number of Days)		30 days

[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] Carrying amount does not include unamortized discount of $3.1 million.

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