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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 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	$ 392	$ 70	$ 1,171	$ 536
Other comprehensive income	107	4	448	27
Dividends ($0.96 per share)			(362)
Employee stock plan			$ (2)
Employee stock plan (in shares)			2.1
Purchase of treasury stock			$ (2,100)
Purchase of treasury stock (in shares)			(21.8)
Balance at end of period	$ 4,512		$ 4,512
Balance at end of period (in shares)	366.4		366.4
Cash dividends (in USD per share)			$ 0.96
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			(64)
Balance at end of period	5,744		5,744
Retained Earnings
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period			6,501
Net income			1,171
Dividends ($0.96 per share)			(362)
Balance at end of period	7,310		7,310
Treasury Stock, at Cost
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period			(6,460)
Employee stock plan			62
Purchase of treasury stock			(2,100)
Balance at end of period	(8,498)		(8,498)
Accumulated Other Comprehensive Loss
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period			(497)	(196)
Other comprehensive income			448
Balance at end of period	$ (49)	$ (169)	$ (49)	$ (169)