v3.26.1
Fair Value of Financial Instruments - Schedule of Plan's Assets Subject to Recurring Fair Value Measurements (Details) - EBP 002 - USD ($)
Dec. 31, 2025
Dec. 31, 2024
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value $ 2,975,548,042 $ 2,792,943,297
U.S. Money Market Fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 143,004 563,134
Commingled Trust Funds U.S.    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 878,739,310 806,333,673
Commingled Trust Funds International    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 49,719,740 32,997,272
U.S. Mutual Funds Equity    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 58,118,174 62,723,278
U.S. Mutual Funds Fixed Income    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 31,024,906 30,068,706
U.S. Mutual Funds Asset Allocation    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 629,996,106 528,892,484
PACCAR Inc Common Stock    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 1,327,806,802 1,331,364,750
Fair Value Hierarchy Level 1    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 2,047,088,992 1,953,612,352
Fair Value Hierarchy Level 1 | U.S. Money Market Fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 143,004 563,134
Fair Value Hierarchy Level 1 | U.S. Mutual Funds Equity    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 58,118,174 62,723,278
Fair Value Hierarchy Level 1 | U.S. Mutual Funds Fixed Income    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 31,024,906 30,068,706
Fair Value Hierarchy Level 1 | U.S. Mutual Funds Asset Allocation    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 629,996,106 528,892,484
Fair Value Hierarchy Level 1 | PACCAR Inc Common Stock    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 1,327,806,802 1,331,364,750
Measured at NAV    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 928,459,050 839,330,945
Measured at NAV | Commingled Trust Funds U.S.    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value 878,739,310 806,333,673
Measured at NAV | Commingled Trust Funds International    
EBP, Investment, Fair Value and NAV [Line Items]    
Financial instruments, at fair value $ 49,719,740 $ 32,997,272