Stock Options and Other Equity-Based Incentive Instruments - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Number of Shares, beginning balance	446,400
Options granted, Number of Shares	0
Options exercised, Number of Shares	0
Options forfeited, Number of Shares	0
Options outstanding, Number of Shares, ending balance	446,400
Options outstanding, Weighted Average Exercise Price, beginning balance	$ 16.84
Options granted, Weighted Average Exercise Price	0
Options exercised, Weighted Average Exercise Price	0
Options forfeited, Weighted Average Exercise Price	0
Options outstanding, Weighted Average Exercise Price, ending balance	$ 16.84
Options Outstanding, Value on Date of Grant	$ 0	$ 0
Options granted, Weighted Average Fair Value	$ 0
Minimum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Option Price per Share, beginning balance	12.63
Options granted, Option Price per Share	0
Options exercised, Option Price per Share	0
Options forfeited, Option Price per Share	0
Options outstanding, Option Price per Share, ending balance	12.63
Maximum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Option Price per Share, beginning balance	23.21
Options granted, Option Price per Share	0
Options exercised, Option Price per Share	0
Options forfeited, Option Price per Share	0
Options outstanding, Option Price per Share, ending balance	$ 23.21