Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 6,617	$ 5,489	$ 17,628	$ 15,293
Less: earnings allocated to participating securities	48	49	125	134
Net income allocated to common shareholders	$ 6,569	$ 5,440	$ 17,503	$ 15,159
Weighted average number of common shares outstanding - basic	35,512	27,550	32,223	26,998
Share-based plans	224	92	131	67
Weighted average number of common shares - diluted	35,736	27,642	32,354	27,065
Basic earnings per share	$ 0.18	$ 0.20	$ 0.54	$ 0.56
Diluted earnings per share	$ 0.18	$ 0.20	$ 0.54	$ 0.56