Summary of Required Compliance Ratios in Connection with Terms of Credit Agreement (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Covenant, Tangible net worth	$ 125,000
Tangible net worth	$ 141,419	$ 147,263
Total leverage	45.60%	44.80%
Secured leverage	8.10%	8.60%
Unencumbered leverage	47.20%	41.40%
Fixed charge coverage	4.80%	4.70%
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%