Note 12 - Fair Value - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Mortgage-backed securities, at fair value (includes pledged assets of $3,946,156 and $3,512,640, respectively)	$ 3,999,906	$ 3,540,002
U.S. Treasury Notes, at fair value (includes pledged assets of $36,806 and $36,382, respectively)	36,806	36,382
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Mortgage-backed securities, at fair value (includes pledged assets of $3,946,156 and $3,512,640, respectively)	0	0
U.S. Treasury Notes, at fair value (includes pledged assets of $36,806 and $36,382, respectively)	36,806	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] | TBA Contracts [Member]
Derivative assets, at fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Mortgage-backed securities, at fair value (includes pledged assets of $3,946,156 and $3,512,640, respectively)	3,999,906	3,540,002
U.S. Treasury Notes, at fair value (includes pledged assets of $36,806 and $36,382, respectively)	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Derivative assets, at fair value	13,972	4,983
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Payer Swaptions [Member]
Derivative assets, at fair value	6,321	27,416
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Interest Rate Cap [Member]
Derivative assets, at fair value	474	1,119
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | TBA Contracts [Member]
Derivative assets, at fair value	(11,034)	(507)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Mortgage-backed securities, at fair value (includes pledged assets of $3,946,156 and $3,512,640, respectively)	0	0
U.S. Treasury Notes, at fair value (includes pledged assets of $36,806 and $36,382, respectively)	0	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] | TBA Contracts [Member]
Derivative assets, at fair value	$ 0	$ 0