Share-Based Compensation - Components of Share Based Compensation Awards (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax compensation expense	$ 1,773	$ 1,492	$ 1,315
Income tax benefit	(547)	(451)	(392)
Total share-based compensation expense, net of income taxes	1,226	1,041	923
Stock and ESPP Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax compensation expense	253	284	237
Income tax benefit	(16)	(23)	(21)
Total share-based compensation expense, net of income taxes	237	261	216
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax compensation expense	1,520	1,208	1,078
Income tax benefit	(531)	(428)	(371)
Total share-based compensation expense, net of income taxes	$ 989	$ 780	$ 707