Stock Based Compensation - Stock Based Compensation Stock Option Activity (Detail) - Employee Stock Option - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of options, outstanding, beginning balance (in shares)	1,210,141
Number of options, granted (in shares)	0
Number of options, exercised (in shares)	(398,239)
Number of options, forfeited (in shares)	0
Number of options, outstanding, ending balance (in shares)	811,902	1,210,141
Number of options, vested and exercisable at December 31, 2016 (in shares)	811,902
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-average exercise price, outstanding, beginning balance (in dollars per share)	$ 16.31
Weighted-average exercise price, granted (in dollars per share)	0.00
Weighted-average exercise price, exercised (in dollars per share)	16.32
Weighted-average exercise price, forfeited (in dollars per share)	0.00
Weighted-average exercise price, outstanding, ending balance (in dollars per share)	16.31	$ 16.31
Weighted average exercise price, vested and exercisable at December 31, 2016 (in dollars per share)	$ 16.31
Aggregate intrinsic value, outstanding, ending balance	$ 27,718	$ 34,638
Weighted-average remaining contractual life, outstanding, ending balance (in years)	2 years 11 months 16 days	3 years 6 months
Aggregate intrinsic value, vested and exercisable at December 31, 2016	$ 27,718
Weighted-average remaining contractual life, vested and exercisable at December 31, 2016 (in years)	2 years 11 months 16 days