v3.26.1
Carrying Amount and Fair Value for Fixed-Rate Loans and Debt (Detail) - USD ($)
$ in Millions
Mar. 31, 2026
Dec. 31, 2025
Assets:    
Due from PACCAR and affiliates $ 1,756.8 $ 1,854.7 [1]
Carrying Amount    
Assets:    
Fixed rate loans 6,391.2 6,536.0
Liabilities:    
Fixed rate debt 7,597.6 7,699.4
Carrying Amount | Related Party    
Assets:    
Due from PACCAR and affiliates 989.6 1,034.6
Carrying Amount | Foreign Finance Affiliates    
Assets:    
Due from PACCAR and affiliates 651.0 702.0
Fair Value    
Assets:    
Fixed rate loans 6,486.4 6,726.7
Liabilities:    
Fixed rate debt 7,648.5 7,803.6
Fair Value | Related Party    
Assets:    
Due from PACCAR and affiliates 999.6 1,052.4
Fair Value | Foreign Finance Affiliates    
Assets:    
Due from PACCAR and affiliates $ 657.4 $ 713.7
[1] The December 31, 2025 balance sheet has been derived from audited financial statements.