Sales and Revenues - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Entity Wide Information Revenue From External Customer [Line Items]
Term used to calculate historical weighted average return rate			5 years
Estimated value of trucks to be returned	$ 558,800,000		$ 558,800,000		$ 473,000,000.0
Estimated sales returned liabilities			588,700,000		503,400,000
Payment to acquire commitment value			1,117,600,000
Payment to acquire commitment related to lease value			384,100,000
Estimated value of returned goods	63,800,000		63,800,000		56,300,000
Sales returns liabilities in estimated returns			145,300,000		126,300,000
Financial Services
Entity Wide Information Revenue From External Customer [Line Items]
Total operating lease income	198,800,000	$ 194,400,000	593,300,000	$ 599,300,000
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	26,300,000	$ 43,700,000	76,600,000	$ 133,500,000
Deferred revenue	103,800,000		103,800,000
Deferred revenue recognize, in 2020	18,800,000		18,800,000
Deferred revenue recognize, in 2021	48,800,000		48,800,000
Deferred revenue recognize, in 2022	21,400,000		21,400,000
Deferred revenue recognize, in 2023	9,600,000		9,600,000
Deferred revenue recognize, in 2024	5,000,000.0		5,000,000.0
Deferred revenue recognize, thereafter	$ 200,000		$ 200,000
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