Commitments and Contingencies - Additional Information (Detail) - USD ($)		204 Months Ended
	Jan. 06, 2017	Dec. 31, 2016	Aug. 31, 2023
Commitments and Contingencies Disclosure [Line Items]
Remedial investigation and feasibility study		$ 110,000,000
Performance Guarantee
Commitments and Contingencies Disclosure [Line Items]
Letter of credit facility outstanding amount			$ 4,900,000
Portland Harbor Superfund Site
Commitments and Contingencies Disclosure [Line Items]
Estimated undiscounted cost	$ 1,700,000,000
Period for remedial action	13 years
Period for monitoring	30 years
Portland Harbor Superfund Site | Minimum
Commitments and Contingencies Disclosure [Line Items]
Accuracy of cost estimate	(30.00%)
Portland Harbor Superfund Site | Maximum
Commitments and Contingencies Disclosure [Line Items]
Accuracy of cost estimate	50.00%