Income Taxes Income Taxes (Tables)

12 Months Ended

Dec. 31, 2011

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

	Year Ended December 31,
	2011			2010		2009
Current:
Federal	$	4,115		$	363	$	3,148
State	2,936			1,870		782
	7,051			2,233		3,930
Deferred:
Federal	(125,261		)	47,709		20,885
State	(24,018		)	4,026		(4,151		)
	(149,279		)	51,735		16,734
Total	$	(142,228	)	$	53,968	$	20,664

Schedule of Deferred Tax Assets and Liabilities

(in thousands)	Year Ended December 31,
	2011			2010
Deferred income tax assets:
Federal benefit of state income taxes	$	(2,479	)	$	6,862
Credit carryforwards	28,783			28,808
Equity and deferred compensation	12,620			11,229
Derivatives	8,669			26,838
Net operating loss	412			14,545
Other, net	29			1,293
	48,034			89,575
Deferred income tax liabilities:
Depreciation and depletion	(219,705		)	(386,440		)
	(219,705		)	(386,440		)
Net deferred income tax liabilities	$	(171,671	)	$	(296,865	)

Schedule of Effective Income Tax Rate Reconciliation

	Year Ended December 31,
	2011		2010		2009
Income tax computed at statutory federal rate	35	%	35	%	35	%
State income taxes, net of federal benefit	3		4		4
Deferred state rate impact	—		(1	)	(5	)
Net impact to uncertain income tax positions	1		—		(2	)
Other	(1	)	2		(2	)
Effective income tax rate	38	%	40	%	30	%

Summary of Income Tax Contingencies

(in millions)	Year Ended December 31,
	2011			2010			2009
Unrecognized income tax benefits at January 1	$	5.2		$	6.1		$	12.0
Decreases for positions taken in current year	—			—			(0.1		)
Decreases for positions taken in a prior year	—			(0.8		)	(1.3		)
Decreases for settlements with taxing authorities	(2.3		)	—			(3.6		)
Decreases for lapses in the applicable statute of limitations	—			(0.1		)	(0.9		)
Unrecognized income tax benefits at December 31	$	2.9		$	5.2		$	6.1

Summary of Income Tax Examinations

Jurisdiction:	Tax Years Subject to Exam:
Federal	2007 - 2010
California	2007 - 2010
Colorado	2007 - 2010
Texas	2007 - 2010
Utah	2008 - 2010