Other Comprehensive Income (Loss) and Shareholders' (Deficit) Equity - Changes in Shareholders' Deficit (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2015			$ (3,590)
Balance at year-end 2015, shares			256.3
Net income	$ 247	$ 240	$ 466	$ 447
Other comprehensive income	4	$ 2	23	$ (18)
Cash dividends ($0.55 per share)			(140)
Employee stock plan			$ 4
Employee stock plan, shares			1.8
Purchase of treasury stock			$ (225)
Purchase of treasury stock, shares			(3.7)
Balance at June 30, 2016	$ (3,462)		$ (3,462)
Balance at June 30, 2016, shares	254.4		254.4
Cash dividends, per share (in USD per share)			$ 0.55
Additional Paid-in- Capital
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2015			$ 2,821
Employee stock plan			(34)
Balance at June 30, 2016	$ 2,787		2,787
Retained Earnings
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2015			4,878
Net income			466
Cash dividends ($0.55 per share)			(140)
Employee stock plan			(19)
Balance at June 30, 2016	5,185		5,185
Treasury Stock, at Cost
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2015			(11,098)
Employee stock plan			57
Purchase of treasury stock			(225)
Balance at June 30, 2016	(11,266)		(11,266)
Accumulated Other Comprehensive Loss
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2015			(196)
Other comprehensive income			23
Balance at June 30, 2016	(173)		(173)
Class A Common Stock
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2015			5
Balance at June 30, 2016	$ 5		$ 5