v3.26.1
Amount of Loss (Gain) from Derivative Financial Instruments Recorded in Consolidated Statements of Comprehensive Income (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Interest-Rate Contracts        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) $ 26.9 $ 113.5 $ 73.8 $ 176.9
Interest-Rate Contracts | Financial Services | Location, Statement of Income, Balance [Axis]: pcar:InterestAndOtherBorrowingExpense        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) 26.9 113.5 73.8 176.9
Foreign-exchange contracts        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) (6.9) 34.4 17.7 36.9
Foreign-exchange contracts | Truck, Parts and Other        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) (2.4) 27.6 15.9 24.2
Foreign-exchange contracts | Truck, Parts and Other | Location, Statement of Income, Balance [Axis]: us-gaap:OtherNonoperatingIncomeExpense | Not designated as hedging instruments        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) 3.1 6.5 2.2 7.8
Foreign-exchange contracts | Truck, Parts and Other | Location, Statement of Income, Balance [Axis]: pcar:InterestAndOtherBorrowingExpense | Not designated as hedging instruments        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) (7.6) (0.2) (9.0) (0.1)
Foreign-exchange contracts | Financial Services | Location, Statement of Income, Balance [Axis]: us-gaap:CostOfGoodsAndServicesSold | Not designated as hedging instruments        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) (0.8) 0.3 (0.7) (0.4)
Foreign-exchange contracts | Financial Services | Location, Statement of Income, Balance [Axis]: pcar:InterestAndOtherBorrowingExpense        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) (4.5) 6.8 1.8 12.7
Cash Flow Hedging | Interest-Rate Contracts | Financial Services | Location, Statement of Income, Balance [Axis]: pcar:InterestAndOtherBorrowingExpense        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) 26.9 113.1 73.5 175.5
Cash Flow Hedging | Foreign-exchange contracts | Truck, Parts and Other | Location, Statement of Income, Balance [Axis]: us-gaap:CostOfGoodsAndServicesSold        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) 0.2 (1.3) 1.9 (10.8)
Cash Flow Hedging | Foreign-exchange contracts | Truck, Parts and Other | Location, Statement of Income, Balance [Axis]: us-gaap:OtherNonoperatingIncomeExpense        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) (4.9) 17.8 11.8 30.2
Cash Flow Hedging | Foreign-exchange contracts | Truck, Parts and Other | Location, Statement of Income, Balance [Axis]: us-gaap:Revenues        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) 1.4 6.8 5.8 4.0
Cash Flow Hedging | Foreign-exchange contracts | Financial Services | Location, Statement of Income, Balance [Axis]: pcar:InterestAndOtherBorrowingExpense        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) 3.1 7.0 10.8 12.8
Net Investment Hedging | Foreign-exchange contracts | Truck, Parts and Other | Location, Statement of Income, Balance [Axis]: us-gaap:OtherNonoperatingIncomeExpense        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain) $ (1.4) (2.5) (5.1) (6.6)
Fair Value Hedging | Interest-Rate Contracts | Financial Services | Location, Statement of Income, Balance [Axis]: pcar:InterestAndOtherBorrowingExpense        
Derivative Instruments Gain Loss [Line Items]        
Derivatives designated as hedging instruments loss (gain)   $ 0.4 $ 0.3 $ 1.4