Other Comprehensive (Loss) Income and Shareholders' Equity - Changes in Shareholders' Equity (Deficit) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period			$ 5,357
Balance at beginning of period (in shares)			386.1
Net income	$ 414	$ 247	$ 779	$ 466
Other comprehensive income	156	4	341	23
Dividends ($0.63 per share)			(240)
Employee stock plan			$ (36)
Employee stock plan (in shares)			1.9
Purchase of treasury stock			$ (1,300)
Purchase of treasury stock (in shares)			(14.0)
Balance at end of period	$ 4,901		$ 4,901
Balance at end of period (in shares)	374.0		374.0
Cash dividends (in USD per share)			$ 0.63
Class A Common Stock
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period			$ 5
Balance at end of period	$ 5		5
Additional Paid-in- Capital
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period			5,808
Employee stock plan			(96)
Balance at end of period	5,712		5,712
Retained Earnings
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period			6,501
Net income			779
Dividends ($0.63 per share)			(240)
Balance at end of period	7,040		7,040
Treasury Stock, at Cost
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period			(6,460)
Employee stock plan			60
Purchase of treasury stock			(1,300)
Balance at end of period	(7,700)		(7,700)
Accumulated Other Comprehensive Loss
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period			(497)	(196)
Other comprehensive income			341
Balance at end of period	$ (156)	$ (173)	$ (156)	$ (173)