Segments Information - Other Interest Expense, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segments Information
Other interest expense, net	$ 16,794	$ 11,012	$ 45,740	$ 30,973
Operating Segments
Segments Information
Other interest expense, net	1,362	1,424	4,183	4,380
Corporate, Non-Segment
Segments Information
Other interest expense, net	15,432	9,588	41,557	26,593
Consumer Services and Plans | Operating Segments
Segments Information
Other interest expense, net	1	1	(1)	5
Dealership | Operating Segments
Segments Information
Other interest expense, net	1,183	876	3,626	2,916
Retail | Operating Segments
Segments Information
Other interest expense, net	$ 178	$ 547	$ 558	$ 1,459