Stock-Based Compensation - Annual Activity Of Stock Options (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of Options, Balance at beginning of year	848
Number of Options - Granted	0
Number of Options - Exercised	(20)
Number of Options - Forfeited/expired	(1)
Number of Options, Balance at end of year	827	848
Weighted Average Exercise Price, Balance at beginning of year	$ 2.92
Weighted Average Exercise Price - Granted	0.00
Weighted Average Exercise Price - Exercised	5.28
Weighted Average Exercise Price - Forfeited/expired	0.79
Weighted Average Exercise Price, Balance at end of year	$ 2.87	$ 2.92
Aggregate Intrinsic Value - Beginning of Year	$ 54
Aggregate Intrinsic Value - Granted
Aggregate Intrinsic Value - Exercised	$ 1	$ 6	$ 23
Aggregate Intrinsic Value - End of Year	$ 28	$ 54
Weighted Average Remaining Contractual Term	3 years 4 months	4 years 4 months