Earnings per Share - Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Earnings Per Share, Basic and Diluted [Abstract]
Net income	$ 6,918	$ 58	$ 5,240	$ 7,289	$ 7,158	$ 7,528	$ 6,466	$ 6,116	$ 19,505	$ 27,268	$ 22,231
Net income allocated to unvested restricted stock									(167)	(204)	(245)
Net income allocated to common shares									$ 19,338	$ 27,064	$ 21,986
Denominator for basic earnings per share—weighted-average shares outstanding	26,300	26,273	19,434	19,402	19,356	19,337	19,501	19,776	22,871	19,491	16,056
Effect of dilutive securities—employee stock options									60	31	23
Denominator for diluted earnings per share—adjusted weighted-average shares outstanding	26,436	26,340	19,469	19,433	19,395	19,368	19,530	19,800	22,931	19,522	16,079
Basic earnings per share	$ 0.27	$ 0.00	$ 0.27	$ 0.37	$ 0.37	$ 0.39	$ 0.33	$ 0.31	$ 0.85	$ 1.39	$ 1.37
Diluted earnings per share	$ 0.27	$ 0.00	$ 0.27	$ 0.37	$ 0.37	$ 0.39	$ 0.33	$ 0.31	$ 0.84	$ 1.39	$ 1.37
Average anti-dilutive options and awards excluded from computation of diluted earnings per share									355	558	559