Note 8 - Financial Instruments - Financial Instruments Sold, Not Yet Purchased (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Investment securities sold, not yet purchased	$ 62,512	$ 44,439
Other investment sold, not yet repurchased, cost	2,488	7,415
Equity Securities [Member]
Investment securities sold, not yet purchased	0	43
Other investment sold, not yet repurchased, cost	2,488	233
Derivative [Member]
Investment securities sold, not yet purchased	424	11,822
Other investment sold, not yet repurchased, cost	0	7,182
Corporate Bonds and Redeemable Preferred Stock [Member]
Investment securities sold, not yet purchased	32,574	29,206
Municipal Bonds [Member]
Investment securities sold, not yet purchased	0	20
US Government Agencies Debt Securities [Member]
Investment securities sold, not yet purchased	1	0
US Treasury Securities [Member]
Investment securities sold, not yet purchased	$ 29,513	$ 3,348