Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2011

Fair Value Measurements

Assets and liabilities measured at fair value on a recurring basis

(in millions)		Total			Level 1		Level 2			Level 3
Commodity derivatives liability, net
	June 30, 2011	$	(102.4	)	$	—	$	(102.4	)	$	—
	December 31, 2010	$	(113.6	)	$	—	$	(11.8	)	$	(101.8	)

Changes in Level 3 fair value measurements

			Three months ended June 30,					Six months ended June 30,
(in millions)			2011		2010			2011			2010
Fair value liability, beginning of period			$	—	$	(34.5	)	$	(101.8	)	$	(26.0	)
	Transfers out of Level 3(1)			—		—			101.8			—
		Realized and unrealized gain included in earnings		—		41.2			—			41.9
	Settlements			—		(10.7	)		—			(19.9	)
Fair value liability, end of period			$	—	$	(4.0	)	$	—		$	(4.0	)
Total unrealized gain included in earnings related to financial assets and liabilities still on the Condensed Balance Sheet at June 30, 2011 and 2010			$	—	$	30.5		$	—		$	22.0

(1)

During the first quarter of 2011, the inputs used to value oil collars, natural gas collars and natural gas basis swaps were directly or indirectly observable, and these instruments were transferred to level 2.

Schedule of fair values and carrying amounts of debt instruments

	June 30, 2011				December 31, 2010
(in millions)	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
Line of credit	$	13	$	13	$	5	$	5
Senior secured revolving credit facility		395		395		170		170
8.25% Senior subordinated notes due 2016		200		208		200		210
10.25% Senior notes due 2014		440		513		439		518
6.75% Senior notes due 2020		300		300		300		303
	$	1,348	$	1,429	$	1,114	$	1,206