Incentive Compensation Plan - Unvested Target Award (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding, beginning of the year, Shares	137,500	117,000	247,668
Granted, Shares	78,000	84,500	26,000
Vested, Shares	(41,000)	(54,000)	(151,668)
Forfeited, Shares	(3,000)	(10,000)	(5,000)
Outstanding, end of the year, Shares	171,500	137,500	117,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding, beginning of the year, Shares	496,603	525,045	426,596
Granted, Shares	134,929	130,995	276,442
Vested, Shares	(188,700)	(149,480)	(171,637)
Forfeited, Shares	0	(9,957)	(6,356)
Outstanding, end of the year, Shares	442,832	496,603	525,045