Subsequent Events (Details) (USD $)	3 Months Ended		3 Months Ended	0 Months Ended
	Mar. 31, 2012 Senior secured revolving credit facility	Apr. 13, 2012 Senior secured revolving credit facility Credit Agreement Amendment	Mar. 31, 2012 8.25% Senior subordinated notes due 2016	Apr. 09, 2012 8.25% Senior subordinated notes due 2016 Repurchases of Notes	Apr. 03, 2012 Unsecured Debt 10.25% Senior notes due 2014 Repurchases of Notes	Apr. 09, 2012 Unsecured Debt 8.25% Senior subordinated notes due 2016 Repurchases of Notes
Subsequent Event [Line Items]
Credit facility maximum borrowing base	$ 1,287,500,000	$ 1,400,000,000
Lender commitments	1,200,000,000
Extinguishment of Debt, Amount					150,000,000	200,000,000
Aggregate purchase price of notes repurchased					181,500,000
Redemption of subordinated debt			200,000,000	215,500,000
Gains (losses) on extinguishment of debt					(30,700,000)	(10,600,000)
Gains (losses) on extinguishment of debt attributable to premium on extinguishment					(26,200,000)	(8,300,000)
Write-off of net discount and debt issuance costs					4,500,000
Aggregate principal amount outstanding after repurchase					205,300,000
Write off of deferred debt issuance cost						$ 2,300,000