Share-Based Compensation - Schedule of Restricted Stock Units to be Settled in Cash (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning balance of Outstanding, Stock Units to be Settled in Cash	1,842,455	2,288,915
Stock Units to be Settled in Cash, Granted	1,036,720	981,136	2,938,283
Stock Units to be Settled in Cash, Vested	(444,499)	(755,656)
Stock Units to be Settled in Cash, Forfeited	(696,060)	(671,940)	(649,368)
Ending balance of Outstanding, Stock Units to be Settled in Cash	1,738,616	1,842,455	2,288,915