Related Party Transactions - Aircraft Time Sharing Agreement (Details) - Related Party - Aircraft Time Sharing Agreement - Air Transportation Equipment $ in Millions		3 Months Ended		9 Months Ended
	Oct. 22, 2015 aircraft	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2017 aircraft
DriveTime Automotive Group, Inc.
Related Party Transaction [Line Items]
Contractual agreement term	12 months
Contractual agreement, perpetual automatic renewal	12 months
Number of allowable days prior to contract termination with written notice	30 days
Verde Investments, Inc.
Related Party Transaction [Line Items]
Expenses from transactions with related party (less than) | $		$ 1	$ 1	$ 1	$ 1
Verde Investments, Inc. | DriveTime Automotive Group, Inc.
Related Party Transaction [Line Items]
Number of aircrafts | aircraft	2					2