Stock Options and Other Equity-Based Incentive Instruments - Stock Option Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Number of Shares, beginning balance (in shares)	343,000
Options granted, Number of Shares (in shares)	0
Options exercised, Number of Shares (in shares)	(182,500)	(100,400)
Options forfeited, Number of Shares (in shares)	0	(3,000)
Options outstanding, Number of Shares, ending balance (in shares)	160,500	343,000
Options outstanding, Weighted Average Exercise Price, beginning balance (in dollars per share)	$ 16.67
Options granted, Weighted Average Exercise Price (in dollars per share)	0
Options exercised, Weighted Average Exercise Price (in dollars per share)	16.00	$ 16.97
Options forfeited, Weighted Average Exercise Price (in dollars per share)	0	23.21
Options outstanding, Weighted Average Exercise Price, ending balance (in dollars per share)	17.60	16.67
Minimum
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 exercised, Option Price per Share	12.63
Options outstanding, Option Price per Share, ending balance	12.63	12.63
Maximum
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 exercised, Option Price per Share	19.46
Options outstanding, Option Price per Share, ending balance	$ 23.21	$ 23.21