Interim Financial Data (Unaudited) - Schedule of Effect on Previously Reported Quarterly Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interim Reporting [Line Items]
Net income	$ 12,629	$ 7,787	$ 23,725	$ 23,706	$ 8,086	$ 3,744	$ 18,715	$ 17,553	$ 67,847	$ 48,098	$ 41,521
Basic net income per share	$ 0.43	$ 0.27	$ 0.81	$ 0.80	$ 0.26	$ 0.12	$ 0.59	$ 0.55	$ 2.31	$ 1.53	$ 1.28
Diluted net income per share	$ 0.43	$ 0.26	$ 0.80	$ 0.79	$ 0.26	$ 0.12	$ 0.58	$ 0.55	$ 2.29	$ 1.52	$ 1.27
Diluted weighted average common shares outstanding	29,543,842	29,516,718	29,477,870	29,910,292	30,966,682	31,537,010	32,142,939	32,094,828	29,612,669	31,682,509	32,751,074
As Reported [Member]
Interim Reporting [Line Items]
Net income		$ 6,898	$ 23,279	$ 23,402
Basic net income per share		$ 0.24	$ 0.80	$ 0.79
Diluted net income per share		$ 0.23	$ 0.79	$ 0.78
Diluted weighted average common shares outstanding		29,457,653	29,423,845	29,860,730