Stock-Based Incentive Plan - Status of Options Granted Under Long-Term Incentive Plan (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
Shares Under Option
Shares Under Option, Outstanding, Beginning balance | shares	504,908
Shares Under Option, Granted | shares	191,297
Shares Under Option, Expired | shares	(65,500)
Shares Under Option, Forfeited | shares	0
Shares Under Option, Exercised | shares	(47,704)
Share Under Option, Outstanding, Ending balance | shares	583,001
Shares Under Options, Exercisable at March 31, 2017 | shares	210,691
Weighted Average Exercise Price Per Share [Abstract]
Weighted Average Exercise Price Per Share, Outstanding, Beginning balance | $ / shares	$ 19.06
Weighted Average Exercise Price Per Share, Granted | $ / shares	28.15
Weighted Average Exercise Price Per Share, Expired | $ / shares	22.98
Weighted Average Exercise Price Per Share, Forfeited | $ / shares	0.00
Weighted Average Exercise Price Per Share, Exercised | $ / shares	18.04
Weighted Average Exercise Price Per Share, Outstanding, Ending balance | $ / shares	21.66
Weighted Average Exercise Price Per Share, Exercisable at March 31, 2017 | $ / shares	$ 17.96
Weighted Average Remaining Contractual Life, Outstanding at March 31, 2017	7 years 10 months 24 days
Weighted Average Remaining Contractual Life, Exercisable at March 31, 2017	6 years
Aggregate Intrinsic Value, Outstanding at March 31, 2017 | $	$ 2,898
Aggregate Intrinsic Value, Exercisable at March 31, 2017 | $	$ 1,672