Note 6 - Fair Values of Assets and Liabilities - Quantitative Information about Level 3 Assets and Liabilities Fair Value Measurements (Details) $ in Thousands	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Loans, interest and fees receivable, at fair value	$ 846,160	$ 417,098
Notes Payable Associated with Structured Financings, Fair Value	2,221	2,919
Valuation Technique, Discounted Cash Flow [Member]
Notes Payable Associated with Structured Financings, Fair Value	2,221	2,919
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Gross Yield [Member]
Loans, interest and fees receivable, at fair value	$ 846,160	$ 417,098
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Gross Yield [Member] | Minimum [Member]
Loans and fees receivable, measurement input	0.229	0.227
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Gross Yield [Member] | Maximum [Member]
Loans and fees receivable, measurement input	0.541	0.565
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Gross Yield [Member] | Weighted Average [Member]
Loans and fees receivable, measurement input	0.403	0.433
Notes payable associated with structured financings, measurement input	0.261	0.237
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Constant Prepayment Rate [Member] | Minimum [Member]
Loans and fees receivable, measurement input	0.051	0.039
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Constant Prepayment Rate [Member] | Maximum [Member]
Loans and fees receivable, measurement input	0.116	0.114
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Constant Prepayment Rate [Member] | Weighted Average [Member]
Loans and fees receivable, measurement input	0.100	0.085
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Prepayment Rate [Member] | Weighted Average [Member]
Notes payable associated with structured financings, measurement input	0.051	0.039
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Default Rate [Member] | Minimum [Member]
Loans and fees receivable, measurement input	0.053	0.069
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Default Rate [Member] | Maximum [Member]
Loans and fees receivable, measurement input	0.317	0.314
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Default Rate [Member] | Weighted Average [Member]
Loans and fees receivable, measurement input	0.273	0.248
Notes payable associated with structured financings, measurement input	0.073	0.079
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Servicing Rate [Member] | Minimum [Member]
Loans and fees receivable, measurement input	0.032	0.029
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Servicing Rate [Member] | Maximum [Member]
Loans and fees receivable, measurement input	0.113	0.142
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Servicing Rate [Member] | Weighted Average [Member]
Loans and fees receivable, measurement input	0.044	0.043
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Discount Rate [Member] | Minimum [Member]
Loans and fees receivable, measurement input	0.127	0.128
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Discount Rate [Member] | Maximum [Member]
Loans and fees receivable, measurement input	0.135	0.135
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Discount Rate [Member] | Weighted Average [Member]
Loans and fees receivable, measurement input	0.130	0.133
Notes payable associated with structured financings, measurement input	0.127	0.132