Schedule of Balance Sheet Information Related to Leases (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
OPERATING LEASES
Total right-of-use assets	$ 39.9	$ 36.9
Total lease liabilities	40.3	37.7
FINANCE LEASES
Total right-of-use assets	1.0	1.1
Total lease liabilities	1.0	1.2
Truck, Parts and Other
OPERATING LEASES
Accounts payable, accrued expenses and other	$ 11.4	$ 13.0
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndOtherAccruedLiabilitiesCurrent	us-gaap:AccountsPayableAndOtherAccruedLiabilitiesCurrent
Other liabilities	$ 20.3	$ 19.5
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
FINANCE LEASES
Accounts payable, accrued expenses and other	$ 0.5	$ 0.7
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndOtherAccruedLiabilitiesCurrent	us-gaap:AccountsPayableAndOtherAccruedLiabilitiesCurrent
Other liabilities	$ 0.5	$ 0.5
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Truck, Parts and Other | Other Noncurrent Assets
OPERATING LEASES
Total right-of-use assets	$ 30.9	$ 31.7
FINANCE LEASES
Total right-of-use assets	1.0	1.1
Financial Services | Other Assets
OPERATING LEASES
Total right-of-use assets	9.0	5.2
Financial Services | Accounts Payable, Accrued Expense and Other
OPERATING LEASES
Total lease liabilities	2.0	1.5
Financial Services | Deferred Taxes and Other Liabilities
OPERATING LEASES
Total lease liabilities	$ 6.6	$ 3.7