Earnings Per Share - Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Basic net income per share:
Net income available to common shareholders	$ 10,257	$ 4,805	$ 23,211	$ 21,799
Weighted average common shares outstanding	47,473	46,904	47,104	46,829
Basic net income per share	$ 0.22	$ 0.10	$ 0.49	$ 0.47
Dilutive net income per share:
Net income available to common shareholders	$ 10,257	$ 4,805	$ 23,211	$ 21,799
Weighted average common shares outstanding	47,473	46,904	47,104	46,829
Dilutive stock options and non-vested restricted stock	1,028	1,280	1,057	1,475
Weighted average common shares outstanding for purposes of computing diluted net income per share	48,501	48,184	48,161	48,304
Dilutive net income per share	$ 0.21	$ 0.10	$ 0.48	$ 0.45