Product Support Liabilities - Additional Information (Detail) - Truck, Parts and Other	6 Months Ended
	Jun. 30, 2017
Product Warranty Liability [Line Items]
Standard product warranty, description	The Company generally offers one year warranties covering most of its vehicles and related aftermarket parts. For vehicles equipped with engines manufactured by PACCAR, the Company generally offers two year warranties on the engine.
Standard product warranty, term	1 year
Extended product warranty, description	Optional extended warranty and R&M contracts can be purchased for periods which generally range up to five years.
Maximum
Product Warranty Liability [Line Items]
Extended product warranty, term	5 years
Engines manufactured by PACCAR
Product Warranty Liability [Line Items]
Standard product warranty, term	2 years