Segment Information (Reconciliation Of Segment Profits To Income (Loss) Before Income Taxes) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Segment Information [Abstract]
Segment profits	$ 78,436	$ 119,298
Depreciation, depletion and amortization	(89,582)	(67,930)
Write-down of oil and natural gas properties	(275,864)	0
Accretion of discount on asset retirement obligations	(947)	(857)
General and administrative	(21,505)	(23,423)
Other operating items	(1,625)	(2,457)
Interest expense	(16,764)	(14,816)
Gain on derivative financial instruments	53,865	3,421
Other income	243	160
Equity income (loss)	(7,906)	8,545
Income (loss) before income taxes	$ (281,649)	$ 21,941