Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2013

Fair Value Measurements

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

	Fair Value Measurements at June 30, 2013 Using
Description	Level 1		Level 2		Level 3		Netting and Collateral		(a)	Total Fair Value
Assets:
Commodity derivatives	$	246	$	326	$	—	$	(476	)	$	96
Liabilities:
Commodity derivatives	$	224	$	369	$	—	$	(529	)	$	64

	Fair Value Measurements at December 31, 2012 Using
Description	Level 1		Level 2		Level 3		Netting and Collateral		(a)	Total Fair Value
Assets:
Commodity derivatives	$	107	$	312	$	—	$	(301	)	$	118
Liabilities:
Commodity derivatives	$	99	$	398	$	—	$	(371	)	$	126

(a)   Represents the impact of netting assets, liabilities and collateral when a legal right of offset exists.