Stock Based Compensation - Stock Based Compensation Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of Options, Granted (in shares)	0	0
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of Options, Outstanding, at December 31, 2016 (in shares)	811,902
Number of Options, Granted (in shares)	0
Number of Options, Exercised (in shares)	(7,970)
Number of Options, Forfeited (in shares)	0
Number of Options, Outstanding, at March 31, 2017 (in shares)	803,932		811,902
Number of Options, Vested and exercisable at March 31, 2017 (in shares)	803,932
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-Average Exercise Price, Outstanding, at December 31, 2016 (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)	23.99
Weighted-Average Exercise Price, Forfeited (in dollars per share)	0.00
Weighted-Average Exercise Price, Outstanding, at March 31, 2017 (in dollars per share)	16.23		$ 16.31
Weighted Average Exercise Price, Vested and exercisable at March 31, 2017 (in dollars per share)	$ 16.23
Aggregate Intrinsic Value, Outstanding	$ 25,031		$ 27,718
Weighted-Average Remaining Contractual Life (in years)	2 years 8 months 12 days		2 years 11 months 15 days
Aggregate Intrinsic Value, Vested and exercisable at March 31, 2017	$ 25,031
Weighted-Average Remaining Contractual Life, Vested and exercisable at March 31, 2017 (in years)	2 years 8 months 12 days