Related Party Transactions - Wholesale Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Related Party Transaction [Line Items]
Net sales and operating revenues, from related parties	$ 3,480	$ 1,544	$ 9,061	$ 3,760
Wholesale vehicle sales
Related Party Transaction [Line Items]
Net sales and operating revenues, from related parties	552	130	1,349	259
Wholesale vehicle sales | DriveTime Automotive Group, Inc.
Related Party Transaction [Line Items]
Net sales and operating revenues, from related parties		$ 1		$ 1
Wholesale vehicle sales | DriveTime Automotive Group, Inc. | Related Party
Related Party Transaction [Line Items]
Net sales and operating revenues, from related parties	$ 15		$ 37