Borrowings and Credit Arrangements - Additional Information (Detail) $ in Millions, $ in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2016 MXN ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Feb. 28, 2022 USD ($)	Dec. 31, 2021 EUR (€)	Dec. 31, 2021 MXN ($)	Dec. 31, 2021 AUD ($)	Dec. 31, 2021 CAD ($)
Debt Disclosure [Line Items]
Interest paid on borrowings		$ 104.8	$ 164.5	$ 203.8
Line of credit, maximum capacity		3,597.0
Line of credit, unused borrowing capacity		3,319.1
Syndicated loan facility
Debt Disclosure [Line Items]
Line of credit, maximum capacity		3,000.0
Line of credit, outstanding amount		0.0
Expires in June 2019 | Syndicated loan facility
Debt Disclosure [Line Items]
Line of credit, maximum capacity		$ 1,000.0
Line of credit, expiry date		2022-06
Expires in June 2022 | Syndicated loan facility
Debt Disclosure [Line Items]
Line of credit, maximum capacity		$ 1,000.0
Line of credit, expiry date		2024-06
Expires in June 2023 | Syndicated loan facility
Debt Disclosure [Line Items]
Line of credit, maximum capacity		$ 1,000.0
Line of credit, expiry date		2026-06
PACCAR's U.S. finance subsidiary | Medium-term Notes
Debt Disclosure [Line Items]
Debt outstanding		$ 5,500.0
Registration expiration		2024-11
PACCAR's U.S. finance subsidiary | Subsequent Event | Medium-term Notes
Debt Disclosure [Line Items]
Debt outstanding					$ 300.0
PACCAR's European finance subsidiary | Medium-term Notes
Debt Disclosure [Line Items]
Debt, unused borrowing capacity | €						€ 1,600,000,000.0
Debt, borrowing capacity | €						€ 2,500,000,000.0
Debt, expiration		2022-07
Debt, renewal period		This program renews annually and expires in July 2022.
PACCAR's Mexico finance subsidiary | Commercial Paper
Debt Disclosure [Line Items]
Maximum limit of borrowing capacity	$ 5,000,000,000.0
PACCAR's Mexico finance subsidiary | Commercial Paper | Maximum
Debt Disclosure [Line Items]
Commercial paper expiration period	1 year
PACCAR's Mexico finance subsidiary | Medium-term Notes
Debt Disclosure [Line Items]
Registration expiration		2026-08
Debt, unused borrowing capacity							$ 9,540,100,000
PACCAR's Mexico finance subsidiary | Medium-term Notes | Commercial Paper
Debt Disclosure [Line Items]
Debt, borrowing capacity	$ 10,000,000,000.0
PACCAR's Australian subsidiary | Medium-term Notes
Debt Disclosure [Line Items]
Debt outstanding								$ 700.0
PACCAR Canadian subsidiary | Medium-term Notes
Debt Disclosure [Line Items]
Debt outstanding									$ 150.0
Financial Services
Debt Disclosure [Line Items]
Commercial paper and term notes borrowings		$ 10,153.9	10,622.4
Fair value hedges and unamortized discounts, net		$ (21.6)	$ (12.7)