v3.26.1
Carrying Amount and Fair Value for Fixed-Rate Loans and Debt (Detail) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Assets:    
Due from PACCAR and affiliates $ 1,722.4 $ 1,854.7 [1]
Carrying Amount    
Assets:    
Fixed rate loans 6,494.8 6,536.0
Liabilities:    
Fixed rate debt 7,742.1 7,699.4
Carrying Amount | Related Party    
Assets:    
Due from PACCAR and affiliates 956.6 1,034.6
Carrying Amount | Foreign Finance Affiliates    
Assets:    
Due from PACCAR and affiliates 646.0 702.0
Fair Value    
Assets:    
Fixed rate loans 6,560.4 6,726.7
Liabilities:    
Fixed rate debt 7,749.1 7,803.6
Fair Value | Related Party    
Assets:    
Due from PACCAR and affiliates 960.1 1,052.4
Fair Value | Foreign Finance Affiliates    
Assets:    
Due from PACCAR and affiliates $ 648.5 $ 713.7
[1] The December 31, 2025 balance sheet has been derived from audited financial statements.