Inventories, net and Notes Payable - Floor Plan, net - Floor Plan Outstanding (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Floor Plan Payable
Less: borrowings, net	$ (40,885)	$ (40,885)
Floor Plan Facility
Floor Plan Payable
Total commitment	1,379,750	1,379,750
Less: borrowings, net	(846,424)	(848,027)
Less: flooring line aggregate interest reduction account	173,853	87,016
Additional borrowing capacity	359,473	444,707
Less: accounts payable for sold inventory	(32,934)	(27,892)
Less: purchase commitments	10,133	8,006
Unencumbered borrowing capacity	316,406	408,809
Line of Credit | Floor Plan Facility
Floor Plan Payable
Total commitment	57,000	60,000
Less: borrowings, net	(40,885)	(40,885)
Additional borrowing capacity	16,115	19,115
Letters of credit | Floor Plan Facility
Floor Plan Payable
Total commitment	15,000	15,000
Less: outstanding letters of credit	(11,175)	(11,175)
Additional letters of credit capacity	$ 3,825	$ 3,825