Commitments and Contingencies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2021 USD ($) Bus_Depot	Dec. 31, 2020 USD ($)
Commitments and Contingencies [Line Items]
Number of bus depot sites received final regulatory closure	3
Number of former bus depot sites	6
Number of bus depot sites continuing monitoring and reporting activities associated with environmental cleanup efforts	3
Number of bus depot sites compliance with environmental cleanup efforts	6
Divestiture [Member]
Commitments and Contingencies [Line Items]
Pension withdrawal liability | $	$ 900,000	$ 900,000
Monthly installment payment for pension withdrawal liability | $	$ 8,100
Term of payment	20 years
Term ending year	2032