Stock-Based Incentive Plan - Compensation Expense Related to Stock Incentive Plans Recognized (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Stock-based compensation expense:
Total Expense	$ 1,740	$ 977
Tax benefit on nonqualified stock option expense, restricted stock awards and disqualifying dispositions of incentive stock options	828	270
Stock Options [Member]
Stock-based compensation expense:
Total Expense	454	338
Restricted Stock Awards [Member]
Stock-based compensation expense:
Total Expense	1,254	606
Employee Stock Purchase Plan [Member]
Stock-based compensation expense:
Total Expense	$ 32	$ 33