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, 2015		$ 544	$ 15,178	$ (1,934)	$ 272
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		3	5
Shares withheld to satisfy tax withholdings			(15)
Share-based compensation and other, net			59
Dividends declared			(106)		(777)
Other comprehensive income	$ 79			79
Net income	584				584
Balance at end of period at Sep. 30, 2016	13,892	547	15,121	(1,855)	79
Balance at beginning of period at Jun. 30, 2016				(1,881)
Increase (Decrease) in Stockholders' Equity
Other comprehensive income	26
Net income	152
Balance at end of period at Sep. 30, 2016	13,892	547	15,121	(1,855)	79
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	5
Shares withheld to satisfy tax withholdings			(16)
Share-based compensation and other, net			59
Dividends declared			(648)		(240)
Other comprehensive income	123			123
Net income	272				272
Balance at end of period at Sep. 30, 2017	12,960	550	14,370	(1,994)	34
Balance at beginning of period at Jun. 30, 2017				(2,050)
Increase (Decrease) in Stockholders' Equity
Other comprehensive income	56
Net income	92
Balance at end of period at Sep. 30, 2017	$ 12,960	$ 550	$ 14,370	$ (1,994)	34
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