CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Millions, except Share data, unless otherwise specified	Total	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME	RETAINED EARNINGS
Balance at Dec. 31, 2011		$ 619	$ 18,901	$ (1,012)	$ 2,319
Balance (in shares) at Dec. 31, 2011		619,000,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		2	33
Issuance of common stock through dividend reinvestment, incentive and benefit plans (in shares)		2,000,000
Shares withheld to satisfy tax withholdings			(11)
Share-based compensation and other, net			27
Other comprehensive income	12			12
Net income	200				200
Dividends declared					(452)
Balance at Mar. 31, 2012	20,638	621	18,950	(1,000)	2,067
Balance (in shares) at Mar. 31, 2012		621,000,000
Balance at Dec. 31, 2012	19,289	626	19,079	(1,701)	1,285
Balance (in shares) at Dec. 31, 2012	625,658,000	626,000,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		1	12
Issuance of common stock through dividend reinvestment, incentive and benefit plans (in shares)		1,000,000
Repurchase of common stock	(386)	(11)	(407)
Repurchase of common stock (in shares)	(11,100,000)	(11,000,000)
Shares withheld to satisfy tax withholdings			(11)
Share-based compensation and other, net			18
Other comprehensive income	6			6
Net income	298				298
Dividends declared					(339)
Balance at Mar. 31, 2013	$ 18,856	$ 616	$ 18,691	$ (1,695)	$ 1,244
Balance (in shares) at Mar. 31, 2013	615,564,000	616,000,000