Inventories and Floor Plan Payables - Floor Plan Payable (Details) $ in Thousands		6 Months Ended	12 Months Ended
	May 12, 2020	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 01, 2020	May 11, 2020
Floor Plan Facility
Floor Plan Payable
Period for temporary reduction in consolidated current ratio	4 months
Number of days into 2021 the notice can be given	7 days
Maximum borrowing capacity		$ 1,379,750	$ 1,379,750
Quarterly reduction in maximum borrowing capacity		3,000
FLAIR offset account amount		130,200	133,600
FLAIR Maximum Percentage	30.00%			20.00%	20.00%
Letters of credit | Floor Plan Facility
Floor Plan Payable
Maximum borrowing capacity		15,000
Line of Credit | Floor Plan Facility
Floor Plan Payable
Maximum borrowing capacity		$ 42,000	$ 48,000
Line of Credit | Notes Payable to Banks | Floor Plan Facility, floor plan notes | London Interbank Offered Rate (LIBO)
Floor Plan Payable
Variable rate spread (as a percent)		2.05%	2.05%
Variable rate basis (as a percent)		0.09	0.15
Line of Credit | Notes Payable to Banks | Floor Plan Facility, floor plan notes | London Interbank Offered Rate (LIBO) | Minimum
Floor Plan Payable
Variable rate spread (as a percent)		2.05%
Line of Credit | Notes Payable to Banks | Floor Plan Facility, floor plan notes | London Interbank Offered Rate (LIBO) | Maximum
Floor Plan Payable
Variable rate spread (as a percent)		2.50%
Line of Credit | Notes Payable to Banks | Floor Plan Facility, floor plan notes | Base Rate | Minimum
Floor Plan Payable
Variable rate spread (as a percent)			0.55%
Line of Credit | Notes Payable to Banks | Floor Plan Facility, floor plan notes | Base Rate | Maximum
Floor Plan Payable
Variable rate spread (as a percent)			1.00%