Borrowings and Credit Arrangements - Additional Information (Detail) In Millions, unless otherwise specified	12 Months Ended				12 Months Ended		1 Months Ended			12 Months Ended		12 Months Ended					12 Months Ended						1 Months Ended	12 Months Ended
	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2013 Syndicated revolving loan facility USD ($)	Dec. 31, 2013 Parent Company Medium-term Notes USD ($)	Dec. 31, 2013 PACCAR's European finance subsidiary Medium-term Notes EUR (€)	Apr. 30, 2011 PACCAR Mexico Medium-term Notes MXN	Dec. 31, 2013 PACCAR Mexico Medium-term Notes MXN	Apr. 30, 2011 PACCAR Mexico Commercial Papers MXN	Dec. 31, 2013 PACCAR Financial Corp. (PFC) Medium-term Notes USD ($)	Nov. 30, 2012 PACCAR Financial Corp. (PFC) Medium-term Notes	Dec. 31, 2013 Truck, Parts and Other USD ($)	Dec. 31, 2012 Truck, Parts and Other USD ($)	Dec. 31, 2011 Truck, Parts and Other USD ($)	Dec. 31, 2013 Truck, Parts and Other Notes 6.90 Percent Due 2014 USD ($)	Dec. 31, 2012 Truck, Parts and Other Notes 6.90 Percent Due 2014 USD ($)	Dec. 31, 2013 Financial Services USD ($)	Dec. 31, 2012 Financial Services USD ($)	Dec. 31, 2013 Financial Services Medium-term Notes	Dec. 31, 2012 Financial Services Medium-term Notes	Dec. 31, 2013 Financial Services Commercial Papers USD ($)	Dec. 31, 2012 Financial Services Commercial Papers USD ($)	Apr. 30, 2011 Maximum PACCAR Mexico Commercial Papers	Dec. 31, 2013 Matures in June 2014 Syndicated revolving loan facility USD ($)	Dec. 31, 2013 Matures in June 2017 Syndicated revolving loan facility USD ($)	Dec. 31, 2013 Matures in June 2018 Syndicated revolving loan facility USD ($)
Debt Disclosure [Line Items]
Notes payable, Non-current															$ 150.0	$ 150.0
Interest rate															6.90%	6.90%	1.70%	1.80%	5.00%	5.50%	1.20%	1.10%
Maturity month and year															2014-02	2014-02
Commercial paper and term notes																	5,765.3	4,167.4			8,032.1	7,492.4
Fair value hedges and unamortized discounts, net																	1.5	6.3
Interest paid on borrowings	149.3	149.9	192.1
Capitalized interest												10.3	10.3	10.3
Debt outstanding					500.0					3,850.0							8,272.7				2,267.8
Registration expiration					Fourth quarter of 2014		2016			Fourth quarter of 2015
Registration expiration period											3 years
Debt, unused borrowing capacity						418.5		7,380.0
Debt, borrowing capacity						1,500.0	10,000.0
Debt, renewal period						second quarter of 2013
Commercial paper expiration period																							1 year
Maximum limit of borrowing capacity									5,000.0
Line of credit, maximum capacity	3,707.9			3,000.0																				1,000.0	1,000.0	1,000.0
Line of credit, unused borrowing capacity	$ 3,465.8
Line of credit, maturity date																								2014-06	2017-06	2018-06