Note 8 - Fair Value Disclosures - Fair Value Measurements of Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent) (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2021	Dec. 31, 2020
Other investments, at fair value		$ 5,516	$ 2,548
U.S. Insurance JV [Member]
Other investments, at fair value	[1]	3,581	1,564
Unfunded commitments	[1]		1,567
SPAC Fund [Member]
Other investments, at fair value	[2]	$ 1,935	$ 984
Redemption notice period (Day)	[2]	90 days	90 days

[1] The U.S. Insurance JV invests in USD denominated debt issued by small and medium size insurance and reinsurance companies.

[2] The SPAC Fund invests in equity interests of SPACs.