Finance Receivables - Activity in allowance for credit losses (Details 1) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2021	Mar. 31, 2020
Accounts Notes And Loans Receivable [Line Items]
Provision for credit losses	$ 250	$ 650	$ 3,050	$ 3,300	$ 3,919	$ 4,597	$ 4,000	$ 4,385	$ 7,250	$ 16,901
Finance receivables
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of year				11,162				16,932	11,162	16,932
Provision for credit losses									7,250	16,901
Charge-offs									(17,823)	(29,837)
Recoveries									5,565	7,166
Balance at end of year	6,154				11,162				6,154	11,162
Finance receivables | Indirect
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of year				10,433				16,575	10,433	16,575
Provision for credit losses									7,250	16,096
Charge-offs									(17,141)	(29,174)
Recoveries									5,459	6,936
Balance at end of year	6,001				10,433				6,001	10,433
Finance receivables | Direct
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of year				$ 729				$ 357	729	357
Provision for credit losses										805
Charge-offs									(682)	(663)
Recoveries									106	230
Balance at end of year	$ 153				$ 729				$ 153	$ 729