CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	ACCUMULATED OTHER COMPREHENSIVE LOSS	RETAINED EARNINGS
Balance at beginning of period at Dec. 31, 2014		$ 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)
Share-based compensation and other, net			17
Other comprehensive income	$ 16			16
Net income	192				192
Dividends declared			105		198
Balance at end of period at Mar. 31, 2015	14,765	566	16,059	(2,001)	141
Balance at beginning of period at Dec. 31, 2015	14,060	544	15,178	(1,934)	272
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		2	2
Repurchase of common stock		0	0
Shares withheld to satisfy tax withholdings			(12)
Share-based compensation and other, net			16
Other comprehensive income	27			27
Net income	236				236
Dividends declared			0		295
Balance at end of period at Mar. 31, 2016	$ 14,036	$ 546	$ 15,184	$ (1,907)	$ 213