Note 4 - Derivative and Other Hedging Instruments - Schedule of Fair Value of Derivative Instruments (Details) - Payer Swaptions [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Long [Member]
Cost	$ 47,706	$ 36,690
Net Estimated Fair Value	$ 33,398	$ 21,493
Weighted average months to expiration (Year)	29 years 9 months 18 days	14 years 8 months 12 days
Notional amount	$ (1,370,000)	$ (1,658,500)
Average fixed pay rate	3.91%	2.27%
Average adjustable rate (Year)	3 months	3 months
Weighted average term (Year)	10 years	11 years 10 months 24 days
Notional Amount	$ 1,370,000	$ 1,658,500
Long [Member] | Less than or Equal to One Year [Member]
Cost	36,685	4,000
Net Estimated Fair Value	$ 21,253	$ 1,575
Weighted average months to expiration (Year)	9 years 7 months 6 days	3 years 2 months 12 days
Notional amount	$ (1,250,000)	$ (400,000)
Average fixed pay rate	4.09%	1.66%
Average adjustable rate (Year)		3 months
Weighted average term (Year)	10 years	5 years
Notional Amount	$ 1,250,000	$ 400,000
Long [Member] | More Than Ten Years [Member]
Cost	11,021
Net Estimated Fair Value	$ 12,145
Weighted average months to expiration (Year)	239 years 6 months
Notional amount	$ (120,000)
Average fixed pay rate	2.05%
Average adjustable rate (Year)	3 months
Weighted average term (Year)	10 years
Notional Amount	$ 120,000
Long [Member] | One to Two Years [Member]
Cost		32,690
Net Estimated Fair Value		$ 19,918
Weighted average months to expiration (Year)		18 years 4 months 24 days
Notional amount		$ (1,258,500)
Average fixed pay rate		2.46%
Average adjustable rate (Year)		3 months
Weighted average term (Year)		14 years 1 month 6 days
Notional Amount		$ 1,258,500
Short [Member] | Less than or Equal to One Year [Member]
Cost	(17,800)	(16,185)
Net Estimated Fair Value	$ (5,982)	$ (4,423)
Weighted average months to expiration (Year)	3 years 7 months 6 days	5 years 3 months 18 days
Notional amount	$ (917,000)	$ (1,331,500)
Average fixed pay rate	4.09%	2.29%
Average adjustable rate (Year)	3 months	3 months
Weighted average term (Year)	10 years	11 years 4 months 24 days
Notional Amount	$ 917,000	$ 1,331,500