Sales and Revenues - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Entity Wide Information Revenue From External Customer [Line Items]
Term used to calculate historical weighted average return rate			7 years
Estimated value of trucks to be returned	$ 672,900,000		$ 672,900,000		$ 627,900,000
Estimated sales returned liabilities			702,600,000		664,100,000
Payment to acquire commitment value			1,194,500,000
Payment to acquire commitment related to lease value			267,000,000.0
Estimated value of returned goods	74,200,000		74,200,000		62,200,000
Sales returns liabilities in estimated returns	173,800,000		173,800,000		142,000,000.0
Financial Services
Entity Wide Information Revenue From External Customer [Line Items]
Total operating lease income	206,400,000	$ 198,800,000	627,900,000	$ 593,300,000
Financing receivable, recorded investment, 90 days past due and still accruing	0		0		$ 0
Trucks | Truck Sales
Entity Wide Information Revenue From External Customer [Line Items]
Total operating lease income	24,900,000	$ 26,300,000	75,200,000	$ 76,600,000
Deferred revenue	81,400,000		81,400,000
Deferred revenue recognize, in 2021	11,100,000		11,100,000
Deferred revenue recognize, in 2022	30,900,000		30,900,000
Deferred revenue recognize, in 2023	17,800,000		17,800,000
Deferred revenue recognize, in 2024	12,900,000		12,900,000
Deferred revenue recognize, in 2025	$ 8,700,000		$ 8,700,000
Minimum
Entity Wide Information Revenue From External Customer [Line Items]
Lease and guarantee periods (in years)			3 years
Minimum | Financial Services
Entity Wide Information Revenue From External Customer [Line Items]
Finance leases, lease term			3 years
Operating lease term	3 years		3 years
Maximum
Entity Wide Information Revenue From External Customer [Line Items]
Lease and guarantee periods (in years)			5 years
Warranty period			5 years
Maximum | Financial Services
Entity Wide Information Revenue From External Customer [Line Items]
Finance leases, lease term			5 years
Operating lease term	5 years		5 years