Earnings per Share - Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share Basic And Diluted [Abstract]
Numerator for basic and diluted earnings per share-income available to common shareholders	$ 5,080	$ 4,830	$ 10,806	$ 10,228
Denominator for basic earnings per share-weighted-average shares outstanding	16,243	16,696	16,250	16,742
Effect of dilutive securities-employee stock options and awards	86	51	86	54
Denominator for diluted earnings per share-adjusted weighted-average shares outstanding	16,329	16,747	16,336	16,796
Basic earnings per share	$ 0.31	$ 0.29	$ 0.67	$ 0.61
Diluted earnings per share	$ 0.31	$ 0.29	$ 0.66	$ 0.61
Average anti-dilutive options and awards excluded from computation of diluted earnings per share	521	668	502	661