v3.26.1
Amounts Outstanding Including Foreign Finance Affiliates (Detail) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Accounts, Notes, Loans and Financing Receivable, Unclassified [Abstract]    
Loans due from PACCAR/ foreign affiliates $ 10,934.3 $ 11,058.1
Accounts Payable and Accrued Liabilities [Abstract]    
Due to PACCAR and affiliates 39.1 21.5 [1]
Related Party [Member]    
Accounts, Notes, Loans and Financing Receivable, Unclassified [Abstract]    
Due from PACCAR and affiliates 1,722.4 1,854.7
Accounts Payable and Accrued Liabilities [Abstract]    
Due to PACCAR and affiliates 39.1 21.5
Related Party [Member] | Affiliated Entity [Member]    
Accounts, Notes, Loans and Financing Receivable, Unclassified [Abstract]    
Loans due from PACCAR/ foreign affiliates 1,051.6 1,129.6
Accounts Payable and Accrued Liabilities [Abstract]    
Tax-related payable due to PACCAR 8.6 6.0
Related Party [Member] | Foreign Finance Affiliates    
Accounts, Notes, Loans and Financing Receivable, Unclassified [Abstract]    
Loans due from PACCAR/ foreign affiliates 646.0 702.0
Related Party [Member] | Other Affiliates [Member]    
Accounts, Notes, Loans and Financing Receivable, Unclassified [Abstract]    
Receivables 24.8 23.1
Accounts Payable and Accrued Liabilities [Abstract]    
Payables $ 30.5 $ 15.5
[1] The December 31, 2025 balance sheet has been derived from audited financial statements.