Stock-Based Incentive Plan - Compensation Expense Related to Stock Incentive Plans Recognized (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock-based compensation expense:
Total Expense	$ 2,151	$ 1,474	$ 1,188
Tax benefit on nonqualified stock option expense, restricted stock awards and disqualifying dispositions of incentive stock options	836	339	244
Stock Options [Member]
Stock-based compensation expense:
Total Expense	577	528	463
Restricted Stock Awards [Member]
Stock-based compensation expense:
Total Expense	1,507	893	679
Employee Stock Purchase Plan [Member]
Stock-based compensation expense:
Total Expense	$ 67	$ 53	$ 46