CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Millions, unless otherwise specified	Total	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	ACCUMULATED OTHER COMPREHENSIVE LOSS	RETAINED EARNINGS
Balance at beginning of period at Dec. 31, 2013		$ 584	$ 17,343	$ (802)	$ 66
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		1	6
Repurchase of common stock		(10)	(298)
Shares withheld to satisfy tax withholdings			(9)
Net income	203				203
Dividends declared			(184)		(125)
Share-based compensation and other, net			16
Other comprehensive income	7			7
Balance at end of period at Mar. 31, 2014	16,798	575	16,874	(795)	144
Balance at beginning of period at Dec. 31, 2014	15,023	569	16,324	(2,017)	147
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		2	6
Repurchase of common stock		(5)	(168)
Shares withheld to satisfy tax withholdings			(15)
Net income	192				192
Dividends declared			(105)		(198)
Share-based compensation and other, net			17
Other comprehensive income	16			16
Balance at end of period at Mar. 31, 2015	$ 14,765	$ 566	$ 16,059	$ (2,001)	$ 141