Treasury Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Oct. 17, 2016
Equity, Class of Treasury Stock [Line Items]
Aggregate stock authorized for repurchase program (shares)		$ 300.0
Remaining authorized repurchase amount	$ 129.4
Treasury stock (shares)	64,543,494
2004 Amended and Restated Stock Incentive Plan
Equity, Class of Treasury Stock [Line Items]
Treasury shares issued for restricted stock units that vested during the period	279,840
Average cost of treasury shares that were issued for restricted stock units that vested during the period (usd per share)	$ 3.14
Shares repurchased to satisfy minimum employee withholding tax requirements resulting from the vesting of such restricted stock units (shares)	96,182
Average cost per share of treasury stock acquired to satisfy minimum employee withholding requirements (usd per share)	$ 28.55