Earnings per Share - 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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share, Basic and Diluted [Abstract]
Numerator for basic and diluted earnings per share—income available to common shareholders	$ 6,235	$ 6,039	$ 17,041	$ 16,267
Denominator for basic earnings per share—weighted-average shares outstanding	16,226	16,658	16,241	16,714
Effect of dilutive securities—employee stock options and awards	88	84	90	61
Denominator for diluted earnings per share—adjusted weighted-average shares outstanding	16,314	16,742	16,331	16,775
Basic earnings per share	$ 0.38	$ 0.36	$ 1.05	$ 0.97
Diluted earnings per share	$ 0.38	$ 0.36	$ 1.04	$ 0.97
Average anti-dilutive options and awards excluded from computation of diluted earnings per share	503	470	499	567