Stock-Based Incentive Plan - Compensation Expense Related to Stock Incentive Plans Recognized (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock-based compensation expense:
Total Expense	$ 1,474	$ 1,188	$ 1,016
Tax benefit on nonqualified stock option expense and restricted stock awards	339	244	162
Stock Options [Member]
Stock-based compensation expense:
Total Expense	528	463	517
Restricted Stock Awards [Member]
Stock-based compensation expense:
Total Expense	893	679	461
Employee Stock Purchase Plan [Member]
Stock-based compensation expense:
Total Expense	$ 53	$ 46	$ 38