Earnings Per Share - Computation of Basic and Diluted Earnings per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerators:
Net income	$ 12,074	$ 7,762	$ 21,641	$ 18,910
Denominators:
Basic weighted average common shares outstanding	33,417,079	32,812,155	33,327,169	32,668,620
Dilutive effect of share based awards	790,894	861,514	803,303	883,284
Diluted weighted average common shares outstanding	34,207,973	33,673,669	34,130,472	33,551,904
Earnings per share:
Basic	$ 0.36	$ 0.24	$ 0.65	$ 0.58
Diluted	$ 0.35	$ 0.23	$ 0.63	$ 0.56
Weighted average common shares considered anti- dilutive in computing diluted earnings per share	62,084	179,450	116,922	192,669