Stock-Based Incentive Plan - Status of Options Granted Under Long-Term Incentive Plan (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Shares Under Option
Shares Under Option, Outstanding, Beginning balance | shares	512,735
Shares Under Option, Granted | shares	190,778
Shares Under Option, Expired | shares	(6,356)
Shares Under Option, Forfeited | shares	(40,002)
Shares Under Option, Exercised | shares	(59,750)
Share Under Option, Outstanding, Ending balance | shares	597,405
Shares Under Options, Exercisable at December 31 | shares	253,175
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	24.61
Weighted Average Exercise Price Per Share, Forfeited | $ / shares	26.29
Weighted Average Exercise Price Per Share, Exercised | $ / shares	18.92
Weighted Average Exercise Price Per Share, Outstanding, Ending balance | $ / shares	23.98
Weighted Average Exercise Price Per Share, Exercisable at December 31, 2018 | $ / shares	$ 20.36
Weighted Average Remaining Contractual Life, Outstanding at December 31, 2018	7 years 2 months 12 days
Weighted Average Remaining Contractual Life, Exercisable at December 31, 2018	5 years 6 months
Aggregate Intrinsic Value, Outstanding at December 31, 2018 | $	$ 820
Aggregate Intrinsic Value, Exercisable at December 31, 2018 | $	$ 670