Note 6 - Fair Value - Assets at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Recurring [Member]
Investments, fair value	$ 720,026	$ 458,075
Fair Value, Recurring [Member] \| Money Market Funds [Member]
Investments, fair value	7,066	7,868
Fair Value, Recurring [Member] \| Money Market Funds, Restricted Investments [Member]
Investments, fair value	2,788	1,359
Fair Value, Recurring [Member] \| Debt [Member]
Investments, fair value	686,458	437,317
Fair Value, Recurring [Member] \| Warrant [Member]
Investments, fair value	29,712	20,200
Fair Value, Recurring [Member] \| Other Investments [Member]
Investments, fair value	1,300	200
Fair Value, Recurring [Member] \| Equity Securities [Member]
Investments, fair value	2,556	358
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Investments, fair value	140	155
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Money Market Funds [Member]
Investments, fair value	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Money Market Funds, Restricted Investments [Member]
Investments, fair value	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Debt [Member]
Investments, fair value	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Warrant [Member]
Investments, fair value	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Other Investments [Member]
Investments, fair value	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Investments, fair value	140	155
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Investments, fair value	3,567	363
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Money Market Funds [Member]
Investments, fair value	7,066	7,868
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Money Market Funds, Restricted Investments [Member]
Investments, fair value	2,788	1,359
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Debt [Member]
Investments, fair value	0	0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Warrant [Member]
Investments, fair value	3,567	363
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Other Investments [Member]
Investments, fair value	0	0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Investments, fair value	0	0
Fair Value, Inputs, Level 3 [Member]
Investments, fair value	716,319	457,557
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member]
Investments, fair value	716,319	457,557
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Money Market Funds [Member]
Investments, fair value	0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Money Market Funds, Restricted Investments [Member]
Investments, fair value	0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Debt [Member]
Investments, fair value	686,458	437,317
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Warrant [Member]
Investments, fair value	26,145	19,837
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Other Investments [Member]
Investments, fair value	1,300	200
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Investments, fair value	$ 2,416	$ 203

Note 6 - Fair Value - Assets at Fair Value on a Recurring Basis (Details) - USD ($)
$ in Thousands

Dec. 31, 2022

Dec. 31, 2021

Fair Value, Recurring [Member]

Investments, fair value

$ 720,026

$ 458,075

Fair Value, Recurring [Member] | Money Market Funds [Member]

Investments, fair value

7,066

7,868

Fair Value, Recurring [Member] | Money Market Funds, Restricted Investments [Member]