Fair Value Measurement (Tables)

6 Months Ended

Jun. 30, 2013

Fair Value Disclosures [Abstract]

Assets (liabilities) measured at fair value on a recurring basis

(in millions)	Total		Level 1		Level 2		Level 3
Commodity derivative asset, net
June 30, 2013	$	53.2	$	—	$	53.2	$	—
December 31, 2012	$	23.2	$	—	$	23.2	$	—

Schedule of fair values and carrying amounts of debt instruments

June 30, 2013	Carrying Amount		Estimated Fair Value
(in millions)			Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	9	$	9	$	—	$	—	$	9
Senior secured revolving credit facility(1)	646		—		646		—		646
10.25% Senior notes due 2014(2)	205		221		—		—		221
6.75% Senior notes due 2020	300		311		—		—		311
6.375% Senior notes due 2022	600		599		—		—		599
	$	1,760	$	1,140	$	646	$	—	$	1,786

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(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 $1.6 million.

December 31, 2012	Carrying Amount		Estimated Fair Value
(in millions)			Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	—	$	—	$	—	$	—	$	—
Senior secured revolving credit facility(1)	563		—		563		—		563
10.25% Senior notes due 2014(2)	205		229		—		—		229
6.75% Senior notes due 2020	300		323		—		—		323
6.375% Senior notes due 2022	600		627		—		—		627
	$	1,668	$	1,179	$	563	$	—	$	1,742

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(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 $2.3 million.