Note 13 - Fair Value - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Mortgage-backed securities	$ 4,520,225	$ 3,540,002
Pledged assets	0	36,382
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Derivative assets, at fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Payer Swaptions [Member]
Derivative assets, at fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Interest Rate Cap [Member]
Derivative assets, at fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Interest Rate Floor [Member]
Derivative assets, at fair value
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | TBA Contracts [Member]
Derivative assets, at fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member]
Mortgage-backed securities	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US Treasury Securities [Member]
Mortgage-backed securities	98,326
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US Treasury Notes Securities [Member]
Pledged assets		36,382
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Derivative assets, at fair value	5,286	4,983
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Payer Swaptions [Member]
Derivative assets, at fair value	1,418	27,416
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Interest Rate Cap [Member]
Derivative assets, at fair value	704	1,119
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Interest Rate Floor [Member]
Derivative assets, at fair value	1,481
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | TBA Contracts [Member]
Derivative assets, at fair value	8,985	(507)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member]
Mortgage-backed securities	4,520,225	3,540,002
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US Treasury Securities [Member]
Mortgage-backed securities	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US Treasury Notes Securities [Member]
Pledged assets		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Derivative assets, at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Payer Swaptions [Member]
Derivative assets, at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Interest Rate Cap [Member]
Derivative assets, at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Interest Rate Floor [Member]
Derivative assets, at fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | TBA Contracts [Member]
Derivative assets, at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member]
Mortgage-backed securities	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | US Treasury Securities [Member]
Mortgage-backed securities	$ 0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | US Treasury Notes Securities [Member]
Pledged assets		$ 0