Segment Information (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Unprecedented personal-injury and other legal matters, net	$ 5	$ 0	$ (6)	$ 0
Assets under vehicle programs	13,022		13,022		$ 9,173
Americas
Segment Reporting Information [Line Items]
Assets under vehicle programs	10,400		10,400		7,200
International
Segment Reporting Information [Line Items]
Assets under vehicle programs	$ 2,600		$ 2,600		$ 2,000