CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	ACCUMULATED OTHER COMPREHENSIVE LOSS	(ACCUMULATED DEFICIT) RETAINED EARNINGS
Balance at beginning of period at Dec. 31, 2015		$ 544	$ 15,178	$ (1,934)	$ 272
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		2	3
Shares withheld to satisfy tax withholdings			(14)
Share-based compensation and other, net			38
Dividends declared			0		(589)
Other comprehensive income	$ 53			53
Net income	432				432
Balance at end of period at Jun. 30, 2016	13,985	546	15,205	(1,881)	115
Balance at beginning of period at Mar. 31, 2016				(1,907)
Increase (Decrease) in Stockholders' Equity
Other comprehensive income	26			26
Net income	196
Balance at end of period at Jun. 30, 2016	13,985	546	15,205	(1,881)	115
Increase (Decrease) in Stockholders' Equity
Cumulative effect of adoption of ASU 2016-09, Improvements to Employee Share-Based Payment Accounting | Restatement adjustment | Accounting Standards Update 2016-09					0
Balance at beginning of period at Dec. 31, 2016	13,399	547	14,970	(2,117)	(1)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		3	3
Shares withheld to satisfy tax withholdings			(15)
Share-based compensation and other, net			38
Dividends declared			(359)		(233)
Other comprehensive income	67			67
Net income	180				180
Balance at end of period at Jun. 30, 2017	13,086	550	14,637	(2,050)	(51)
Balance at beginning of period at Mar. 31, 2017				(2,086)
Increase (Decrease) in Stockholders' Equity
Other comprehensive income	36			36
Net income	17
Balance at end of period at Jun. 30, 2017	$ 13,086	$ 550	$ 14,637	$ (2,050)	(51)
Increase (Decrease) in Stockholders' Equity
Cumulative effect of adoption of ASU 2016-09, Improvements to Employee Share-Based Payment Accounting | Restatement adjustment | Accounting Standards Update 2016-09					$ 3