Stock-Based Incentive Plan - Compensation Expense Related to Stock Incentive Plans Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Stock-based compensation expense:
Total Expense	$ 846	$ 467
Tax benefit on nonqualified stock option expense, restricted stock awards and disqualifying dispositions of incentive stock options	507	151
Stock Options [Member]
Stock-based compensation expense:
Total Expense	221	151
Restricted Stock Awards [Member]
Stock-based compensation expense:
Total Expense	610	300
Employee Stock Purchase Plan [Member]
Stock-based compensation expense:
Total Expense	$ 15	$ 16