Stock-Based Compensation Plans - Summary of Stock Options Issued Pursuant to Stock Incentive Plans (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of Shares
Outstanding, Beginning Balance	5,799,076	5,282,693	7,408,821
Granted	2,284,500	2,055,514	27,132
Exercised	(792,841)	(1,144,273)	(2,036,558)
Forfeited	(446,845)	(394,265)	(116,702)
Expired	(52,515)	(593)
Outstanding, Ending Balance	6,791,375	5,799,076	5,282,693
Number of Shares Exercisable, Ending Balance	3,650,356
Weighted-Average Exercise Price
Beginning Balance	$ 14.37	$ 12.06	$ 11.02
Granted	17.92	19.12	20.13
Exercised	11.69	10.62	8.08
Forfeited	18.69	19.06	17.80
Expired	20.44	20.51
Ending Balance	15.54	$ 14.37	$ 12.06
Weighted-Average Exercise Price Exercisable, Ending Balance	$ 13.15
Weighted-Average Remaining Contractual Term (Years)
Weighted Average Remaining Contractual Term (Years), Outstanding as of end of period	6 years 8 months 5 days
Weighted-Average Remaining Contractual Term (Years), Exercisable as of end of period	4 years 10 months 13 days
Aggregate Intrinsic Value of In-the-Money Options
Aggregate Intrinsic Value of In-the-Money Options, Outstanding as of end of period	$ 20,777,320
Aggregate Intrinsic Value of In-the-Money Options, Exercisable as of end of period	$ 20,245,847