Stock Based Compensation - Stock Based Compensation Stock Option Activity (Detail) - Employee Stock Option - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of Options, Outstanding, beginning balance (in shares)	1,433,179	1,956,515	2,454,634
Number of Options, Granted (in shares)	0	9,794	14,301
Number of Options, Exercised (in shares)	(216,980)	(440,380)	(485,141)
Number of Options, Forfeited (in shares)	(6,058)	(92,750)	(27,279)
Number of Options, Outstanding, ending balance (in shares)	1,210,141	1,433,179	1,956,515
Number of Options, Vested and exercisable at December 31, 2015 (in shares)	1,135,278
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)	$ 16.23	$ 16.25	$ 15.30
Weighted-Average Exercise Price, Granted (in dollars per share)	0.00	27.62	26.76
Weighted-Average Exercise Price, Exercised (in dollars per share)	15.55	14.67	11.32
Weighted-Average Exercise Price, Forfeited (in dollars per share)	24.77	25.20	24.13
Weighted-Average Exercise Price, Outstanding, ending balance (in dollars per share)	16.31	$ 16.23	$ 16.25
Weighted Average Exercise Price, Vested and exercisable at December 31, 2015 (in dollars per share)	$ 15.75
Aggregate Intrinsic Value, Outstanding, ending balance at December 31, 2015	$ 34,638
Weighted-Average Remaining Contractual Life (Years), Outstanding at December 31, 2015 (in years)	3 years 6 months
Aggregate Intrinsic Value, Vested and exercisable at December 31, 2015	$ 33,130
Weighted-Average Remaining Contractual Life (Years), Vested and exercisable at December 31, 2015 (in years)	3 years 3 months 29 days