Summary of Significant Accounting Policies - Contracts in Transit, Accounts Receivable and Current Expected Credit Losses (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
"Shipping, Handling and Transportation Costs [Abstract]"
Number of days for retail installment sales contracts funded after the initial approval of the retail installment sales contract by third party lender	10 days
Accounts receivable due in excess of one year	$ 8,400		$ 8,600
Allowance for doubtful accounts - contracts in transit	200		$ 0
Allowance for doubtful accounts
Balance, beginning of period	3,537	$ 4,398
Charged to bad debt expense	531	379
Deductions	(611)	(131)
Balance, end of period	$ 3,457	$ 4,646