Stock-Based Incentive Plan - Status of Options Granted Under Long-Term Incentive Plan (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares
Shares Under Option
Shares Under Option, Outstanding, Beginning balance | shares	597,405
Shares Under Option, Expired | shares	(7,756)
Shares Under Option, Forfeited | shares	(6,500)
Shares Under Option, Exercised | shares	(30,500)
Share Under Option, Outstanding, Ending balance | shares	552,649
Shares Under Options, Exercisable at March 31, 2019 | shares	384,220
Weighted Average Exercise Price Per Share [Abstract]
Weighted Average Exercise Price Per Share, Outstanding, Beginning balance | $ / shares	$ 23.98
Weighted Average Exercise Price Per Share, Expired | $ / shares	22.99
Weighted Average Exercise Price Per Share, Forfeited | $ / shares	25.53
Weighted Average Exercise Price Per Share, Exercised | $ / shares	17.06
Weighted Average Exercise Price Per Share, Outstanding, Ending balance | $ / shares	24.36
Weighted Average Exercise Price Per Share, Exercisable at March 31, 2019 | $ / shares	$ 22.65
Weighted Average Remaining Contractual Life, Outstanding at March 31, 2019	7 years 2 months 12 days
Weighted Average Remaining Contractual Life, Exercisable at March 31, 2019	6 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding at March 31, 2019 | $	$ 1,321
Aggregate Intrinsic Value, Exercisable at March 31, 2019 | $	$ 1,312