Summary of Geographic Segment Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 5,402	$ 9,172	$ 9,124
Assets exclusive of assets under vehicle programs	8,365	9,311	6,370
Assets under vehicle programs	9,173	13,815	12,779
Long-Lived Assets	2,568	2,691	2,653
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	3,758	5,867	5,708
Assets exclusive of assets under vehicle programs	5,262	5,830	3,494
Assets under vehicle programs	6,797	9,824	9,021
Long-Lived Assets	1,421	1,536	1,476
All Other Countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	1,644	3,305	3,416
Assets exclusive of assets under vehicle programs	3,103	3,481	2,876
Assets under vehicle programs	2,376	3,991	3,758
Long-Lived Assets	$ 1,147	$ 1,155	$ 1,177