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Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		5 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Related Party Transactions
Receivable from related party	$ 184		$ 184	$ 184		$ 349
USAA
Related Party Transactions
Receivable from related party	200		200	200		300
Due to related party	6,000		6,000	6,000		$ 5,300
USAA \| Sales and marketing
Related Party Transactions
Costs under related party agreements	5,700	$ 5,300		11,200	$ 9,800
Accu-Trade
Related Party Transactions
Due to related party	$ 400		$ 400	$ 400
Ownership percent	20.00%		20.00%	20.00%
Accu-Trade \| Contra-revenue
Related Party Transactions
Costs under related party agreements	$ 300		$ 500
Accu-Trade \| Cost of revenue
Related Party Transactions
Costs under related party agreements	$ 300		$ 400