Stock-Based Incentive Plan - Status of Options Granted Under Long-Term Incentive Plan (Detail) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($) $ / shares shares
Shares Under Option
Shares Under Option, Outstanding, Beginning balance | shares	512,735
Shares Under Option, Granted | shares	193,778
Shares Under Option, Expired | shares	0
Shares Under Option, Forfeited | shares	(12,537)
Shares Under Option, Exercised | shares	(36,990)
Share Under Option, Outstanding, Ending balance | shares	656,986
Shares Under Options, Exercisable at June 30, 2018 | shares	279,627
Weighted Average Exercise Price Per Share [Abstract]
Weighted Average Exercise Price Per Share, Outstanding, Beginning balance | $ / shares	$ 21.90
Weighted Average Exercise Price Per Share, Granted | $ / shares	28.50
Weighted Average Exercise Price Per Share, Expired | $ / shares	0.00
Weighted Average Exercise Price Per Share, Forfeited | $ / shares	25.48
Weighted Average Exercise Price Per Share, Exercised | $ / shares	19.21
Weighted Average Exercise Price Per Share, Outstanding, Ending balance | $ / shares	23.93
Weighted Average Exercise Price Per Share, Exercisable at June 30, 2018 | $ / shares	$ 20.26
Weighted Average Remaining Contractual Life, Outstanding at June 30, 2018	7 years 8 months 12 days
Weighted Average Remaining Contractual Life, Exercisable at June 30, 2018	6 years
Aggregate Intrinsic Value, Outstanding at June 30, 2018 | $	$ 2,648
Aggregate Intrinsic Value, Exercisable at June 30, 2018 | $	$ 2,063