European Commission Settlement - Additional Information (Detail) - Truck, Parts and Other € in Millions, $ in Millions			3 Months Ended		6 Months Ended		9 Months Ended
	Jul. 19, 2016 USD ($)	Jul. 19, 2016 EUR (€)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2016 EUR (€)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Loss Contingencies [Line Items]
European Commission charge			$ 0.0	$ 0.0	$ 833.0	€ 752.7	$ 833.0	$ 0.0
Litigation settlement amount	$ 833.0	€ 752.7