Summary of Required Compliance Ratios in Connection with Terms of Credit Agreement (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Covenant, Tangible net worth	$ 125,000
Tangible net worth	$ 150,247	$ 167,181
Total leverage	44.00%	42.30%
Secured leverage	8.80%	9.10%
Unencumbered leverage	40.60%	38.50%
Fixed charge coverage	4.50%	4.00%
Maximum
Debt Instrument [Line Items]
Covenant, Total leverage	60.00%
Covenant, Secured leverage	30.00%
Covenant, Unencumbered leverage	60.00%
Minimum
Debt Instrument [Line Items]
Covenant, Fixed charge coverage	1.50%