Debt (Receivable-Backed Notes Payable) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Receivable-backed notes payable - recourse	$ 74,599	$ 88,569
Receivable backed notes payable - non-recourse	325,206	334,246
Total receivable-backed debt	399,805	422,815
Principal Balance of Pledged/Secured Receivables	476,470	494,604
Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable-backed notes payable - recourse	74,599	88,569
Principal Balance of Pledged/Secured Receivables	92,247	109,277
Non-Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs	(4,438)	(5,125)
Receivable backed notes payable - non-recourse	325,206	334,246
Principal Balance of Pledged/Secured Receivables	384,223	385,327
Liberty Bank Facility [Member] | Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable-backed notes payable - recourse	$ 21,663	$ 25,860
Interest Rate	4.00%	4.75%
Principal Balance of Pledged/Secured Receivables	$ 26,630	$ 31,681
NBA Receivables Facility [Member] | Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable-backed notes payable - recourse	$ 26,484	$ 32,405
Interest Rate	3.50%	4.55%
Principal Balance of Pledged/Secured Receivables	$ 32,870	$ 39,787
Pacific Western Facility [Member] | Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable-backed notes payable - recourse	$ 26,452	$ 30,304
Interest Rate	3.06%	4.68%
Principal Balance of Pledged/Secured Receivables	$ 32,747	$ 37,809
KeyBank/DZ Purchase Facility [Member] | Non-Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable backed notes payable - non-recourse	$ 65,159	$ 31,708
Interest Rate	2.50%	3.99%
Principal Balance of Pledged/Secured Receivables	$ 81,522	$ 39,448
Quorum Purchase Facility [Member] | Non-Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable backed notes payable - non-recourse	36,759	44,525
Principal Balance of Pledged/Secured Receivables	42,836	49,981
2012 Term Securitization [Member] | Non-Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable backed notes payable - non-recourse	$ 6,093	$ 8,638
Interest Rate	2.94%	2.94%
Principal Balance of Pledged/Secured Receivables	$ 7,167	$ 9,878
2013 Term Securitization [Member] | Non-Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable backed notes payable - non-recourse	$ 14,811	$ 18,219
Interest Rate	3.20%	3.20%
Principal Balance of Pledged/Secured Receivables	$ 16,581	$ 19,995
2015 Term Securitization [Member] | Non-Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable backed notes payable - non-recourse	$ 26,426	$ 31,188
Interest Rate	3.02%	3.02%
Principal Balance of Pledged/Secured Receivables	$ 28,707	$ 33,765
2016 Term Securitization [Member] | Non-Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable backed notes payable - non-recourse	$ 40,897	$ 48,529
Interest Rate	3.35%	3.35%
Principal Balance of Pledged/Secured Receivables	$ 46,375	$ 54,067
2017 Term Securitization [Member] | Non-Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable backed notes payable - non-recourse	$ 57,641	$ 65,333
Interest Rate	3.12%	3.12%
Principal Balance of Pledged/Secured Receivables	$ 66,280	$ 74,219
2018 Term Securitization [Member] | Non-Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Receivable backed notes payable - non-recourse	$ 81,858	$ 91,231
Interest Rate	4.02%	4.02%
Principal Balance of Pledged/Secured Receivables	$ 94,755	$ 103,974
Minimum [Member] | Quorum Purchase Facility [Member] | Non-Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Interest Rate	4.75%	4.75%
Maximum [Member] | Quorum Purchase Facility [Member] | Non-Recourse Receivable Backed Notes Payable [Member]
Debt Instrument [Line Items]
Interest Rate	5.50%	5.50%