Statement of Consolidated Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
NET INCOME	$ 1,035	$ 356	$ 1,752	$ 1,153
Commodity cash flow hedge activity, net of tax:
Reclassification of (gain) loss on settled derivative instruments	8	(58)	14	(92)
Change in fair value of derivative instruments	7	111	(1)	112
Commodity cash flow hedge activity, net of tax	15	53	13	20
COMPREHENSIVE INCOME	1,050	409	1,765	1,173
Preferred stock dividends	19	19	38	38
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON STOCK	$ 1,031	$ 390	$ 1,727	$ 1,135