Stock Plans and Other Incentives - Option Activity and Other Plan Data (Detail) - $ / shares	1 Months Ended	12 Months Ended
	May 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding at beginning of period, Options		547,500	582,500	627,724
Granted, Options	20,000	0	0	20,000
Exercised, Options		(17,500)	(35,000)	(56,362)
Cancelled through cash settlement, Options		0	0	(8,862)
Forfeited/cancelled/expired, Options		0	0	0
Outstanding at end of period, Options		530,000	547,500	582,500
Options exercisable at end of period, Options		518,000	531,500	562,500
Options exercisable which can be settled in cash, Options		0	0	0
Weighted average fair value of options granted per year (per option)	$ 7.64	$ 0.00	$ 0.00	$ 7.64
Weighted average remaining contractual life at end of period		2 years	3 years	3 years 10 months 24 days
Outstanding at beginning of period, Weighted-Average Exercise Price		$ 9.61	$ 9.52	$ 9.05
Granted, Weighted-Average Exercise Price	$ 18.52	0.00	0.00	18.52
Exercised, Weighted-Average Exercise Price		(8.74)	(8.12)	(8.25)
Cancelled through cash settlement, Weighted-Average Exercise Price		(0.00)	(0.00)	(4.09)
Forfeited/cancelled/expired, Weighted-Average Exercise Price		0	0	0
Outstanding at end of period, Weighted-Average Exercise Price		9.64	9.61	9.52
Options exercisable at end of period, Weighted-Average Exercise Price		9.44	9.35	9.21
Options exercisable which can be settled in cash, Weighted-Average Exercise Price		$ 0	$ 0	$ 0