Vehicle Service Agreement Liability - Reconciliation of the Changes in the Vehicle Service Agreement (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Movement in Standard Product Warranty Accrual [Roll Forward]
Recognition of service fees on vehicle service agreements	$ (4,200)
Vehicle service agreement fees
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at January 1, net	43,734	$ 40,794
Vehicle service agreement liability acquired during the year related to the purchase of Geminus	10,792	0
Gross service fees for vehicle service agreements sold	6,055	5,169
Recognition of service fees on vehicle service agreements	(5,367)	(4,773)
Liability for claims authorized on vehicle service agreements	1,887	1,372
Payments of claims authorized on vehicle service agreements	(970)	(1,544)
Re-estimation of deferred service fees	(148)	(96)
Balance at March 31, net	$ 55,983	$ 40,922