Revenue From Contracts with Customers - Schedule of Deferred Assets Related to Revenue From Contracts with Customers (Rollforward) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Table of Deferred Assets Related to Revenue From Contracts with Customers [Roll Forward]
Deferred acquisition costs, beginning balance	$ 170,063
Deferred acquisition costs, ending balance	170,727
Customer Contracts
Table of Deferred Assets Related to Revenue From Contracts with Customers [Roll Forward]
Deferred acquisition costs, beginning balance	13,463
Additions	5,741
Amortizations	6,875
Deferred acquisition costs, ending balance	12,329
Customer Contracts | Warranty coverage revenue
Table of Deferred Assets Related to Revenue From Contracts with Customers [Roll Forward]
Deferred acquisition costs, beginning balance	1,274
Additions	79
Amortizations	267
Deferred acquisition costs, ending balance	1,086
Customer Contracts | Car club revenue
Table of Deferred Assets Related to Revenue From Contracts with Customers [Roll Forward]
Deferred acquisition costs, beginning balance	12,189
Additions	5,662
Amortizations	6,608
Deferred acquisition costs, ending balance	$ 11,243