Note 10 - Collateralized Securities Transactions - Secured Borrowings (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Securities sold under agreements to repurchase	$ 457,351	$ 452,797
Receivables under resale agreements	457,528	437,692
Overnight and Continuous [Member]
Securities sold under agreements to repurchase	0
Receivables under resale agreements	0
Maturity Less than 30 Days [Member]
Securities sold under agreements to repurchase	457,351	452,797
Receivables under resale agreements	457,528	437,692
Maturity 30 to 90 Days [Member]
Securities sold under agreements to repurchase	0	0
Receivables under resale agreements	0
Maturity Greater than 90 Days [Member]
Securities sold under agreements to repurchase	0	0
Receivables under resale agreements	0
Collateralized Mortgage-Backed Securities [Member]
Securities sold under agreements to repurchase	457,351	452,797
Receivables under resale agreements	457,528	437,692
Collateralized Mortgage-Backed Securities [Member] | Overnight and Continuous [Member]
Securities sold under agreements to repurchase	0
Receivables under resale agreements	0
Collateralized Mortgage-Backed Securities [Member] | Maturity Less than 30 Days [Member]
Securities sold under agreements to repurchase	457,351	452,797
Receivables under resale agreements	457,528	437,692
Collateralized Mortgage-Backed Securities [Member] | Maturity 30 to 90 Days [Member]
Securities sold under agreements to repurchase	0	0
Receivables under resale agreements	0
Collateralized Mortgage-Backed Securities [Member] | Maturity Greater than 90 Days [Member]
Securities sold under agreements to repurchase	0	$ 0
Receivables under resale agreements	$ 0