Other Comprehensive (Loss) Income 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, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2014			$ (2,200)
Balance at year-end 2014, shares			279.9
Net income	$ 240	$ 192	$ 447	$ 364
Other comprehensive income	2	$ 2	(18)	$ 5
Cash dividends ($0.45 per share)			(124)
Employee stock plan issuance			$ 7
Employee stock plan issuance, shares			2.0
Purchase of treasury stock			$ (1,145)
Purchase of treasury stock, shares			(14.6)
Balance at June 30, 2015	$ (3,033)		$ (3,033)
Balance at June 30, 2015, shares	267.3		267.3
Cash dividends, per share (in USD per share)			$ 0.45
Additional Paid-in- Capital
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2014			$ 2,802
Employee stock plan issuance			(21)
Balance at June 30, 2015	$ 2,781		2,781
Retained Earnings
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2014			4,286
Net income			447
Cash dividends ($0.45 per share)			(124)
Employee stock plan issuance			(36)
Purchase of treasury stock			0
Balance at June 30, 2015	4,573		4,573
Treasury Stock, at Cost
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2014			(9,223)
Employee stock plan issuance			64
Purchase of treasury stock			(1,145)
Balance at June 30, 2015	(10,304)		(10,304)
Accumulated Other Comprehensive Loss
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2014			(70)
Other comprehensive income			(18)
Balance at June 30, 2015	(88)		(88)
Class A Common Stock
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at year-end 2014			5
Balance at June 30, 2015	$ 5		$ 5