Note 10 - Collateralized Securities Transactions - Secured Borrowings (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Securities sold under agreements to repurchase	$ 690,900	$ 408,203
Receivables under resale agreements	692,438	408,408
Overnight and Continuous [Member]
Securities sold under agreements to repurchase	74,322
Receivables under resale agreements	74,378
Maturity Less than 30 Days [Member]
Securities sold under agreements to repurchase	616,578	408,203
Receivables under resale agreements	618,060	408,408
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	690,900	408,203
Receivables under resale agreements	692,438	408,408
Collateralized Mortgage-Backed Securities [Member] | Overnight and Continuous [Member]
Securities sold under agreements to repurchase	74,322
Receivables under resale agreements	74,378
Collateralized Mortgage-Backed Securities [Member] | Maturity Less than 30 Days [Member]
Securities sold under agreements to repurchase	616,578	408,203
Receivables under resale agreements	618,060	408,408
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