Quarterly report pursuant to Section 13 or 15(d)

Long-Term Debt - 2016 Credit Facilities (Details)

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Long-Term Debt - 2016 Credit Facilities (Details) - USD ($)
9 Months Ended
Nov. 30, 2016
Sep. 30, 2020
Dec. 31, 2019
TwoThousandSixteenRevolvingCreditFacilityMember      
Line of Credit Facility [Line Items]      
2016 Revolving Credit Facility   $ 0 $ 0
Revolving Credit Facility | TwoThousandSixteenRevolvingCreditFacilityMember      
Line of Credit Facility [Line Items]      
Line of Credit Facility, Increase (Decrease), Net $ 25,000,000.0    
Current borrowing capacity   245,000,000.0  
Maximum borrowing capacity   295,000,000.0  
Borrowing base   202,100,000  
2016 Revolving Credit Facility   0  
Letters of credit outstanding amount   13,000,000.0  
Borrowing availability amount   189,100,000  
Revolving Credit Facility | 2016 New Vehicle Floor Plan Facility and 2016 Used Vehicle Floor Plan Facility      
Line of Credit Facility [Line Items]      
Current borrowing capacity   966,000,000.0  
Maximum borrowing capacity   $ 1,216,000,000  
Maximum aggregate commitments allocated to commitments under the 2016 Used Vehicle Floor Plan Facility   40.00%  
Revolving Credit Facility | Two Thousand Sixteen Vehicle Floor Plan Facility [Member]      
Line of Credit Facility [Line Items]      
Line of Credit Facility, Increase (Decrease), Net $ 215,000,000.0