Note 10 - Fair Value of Financial Instruments - Schedule of Carrying Values and Fair Values of Financial Assets and Liabilities Recorded at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Common stock investment, at fair value	$ 58,789	$ 58,460
CMBS structured pass-through certificates, at fair value	68,133	$ 69,816
Fair Value, Recurring [Member]
Cash and cash equivalents	35,243
Restricted cash	180
Bridge loan, net	328,150
Real estate investment, net	61,346
Common stock investment, at fair value	58,789
Accrued interest and dividends	10,231
CMBS structured pass-through certificates, at fair value	68,133
Accounts receivable and other assets	1,710
Assets, Fair Value Disclosure, Total	8,039,736
Secured financing agreements, net	720,367
Master repurchase agreements	296,991
Unsecured notes, net	202,695
Mortgages payable, net	32,188
Accounts payable and other accrued liabilities	6,492
Accrued interest payable	7,696
Liabilities, Fair Value Disclosure, Total	7,533,357
Fair Value, Recurring [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Bonds payable held in variable interest entities, at fair value	6,266,928
Fair Value, Recurring [Member] | Bridge Loan [Member]
Bridge loan, net	13,433
Fair Value, Recurring [Member] | Mortgages [Member]
Bridge loan, net	746,286
Fair Value, Recurring [Member] | Mortgages [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Bridge loan, net	6,716,235
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	35,243
Restricted cash	180
Bridge loan, net	0
Real estate investment, net	0
Common stock investment, at fair value	0
Accrued interest and dividends	10,231
CMBS structured pass-through certificates, at fair value	0
Accounts receivable and other assets	1,710
Assets, Fair Value Disclosure, Total	47,364
Secured financing agreements, net	0
Master repurchase agreements	0
Unsecured notes, net	0
Mortgages payable, net	0
Accounts payable and other accrued liabilities	6,492
Accrued interest payable	7,696
Liabilities, Fair Value Disclosure, Total	14,188
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Bonds payable held in variable interest entities, at fair value	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Bridge Loan [Member]
Bridge loan, net	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgages [Member]
Bridge loan, net	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgages [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Bridge loan, net	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents	0
Restricted cash	0
Bridge loan, net	0
Real estate investment, net	0
Common stock investment, at fair value	0
Accrued interest and dividends	0
CMBS structured pass-through certificates, at fair value	68,133
Accounts receivable and other assets	0
Assets, Fair Value Disclosure, Total	6,784,368
Secured financing agreements, net	0
Master repurchase agreements	0
Unsecured notes, net	0
Mortgages payable, net	0
Accounts payable and other accrued liabilities	0
Accrued interest payable	0
Liabilities, Fair Value Disclosure, Total	6,266,928
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Bonds payable held in variable interest entities, at fair value	6,266,928
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Bridge Loan [Member]
Bridge loan, net	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgages [Member]
Bridge loan, net	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgages [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Bridge loan, net	6,716,235
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents	0
Restricted cash	0
Bridge loan, net	328,150
Real estate investment, net	61,346
Common stock investment, at fair value	58,789
Accrued interest and dividends	0
CMBS structured pass-through certificates, at fair value	0
Accounts receivable and other assets	0
Assets, Fair Value Disclosure, Total	1,208,004
Secured financing agreements, net	720,367
Master repurchase agreements	296,991
Unsecured notes, net	202,695
Mortgages payable, net	32,188
Accounts payable and other accrued liabilities	0
Accrued interest payable	0
Liabilities, Fair Value Disclosure, Total	1,252,241
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Bonds payable held in variable interest entities, at fair value	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Bridge Loan [Member]
Bridge loan, net	13,433
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgages [Member]
Bridge loan, net	746,286
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgages [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Bridge loan, net	0
Fair Value, Recurring [Member] | Reported Value Measurement [Member]
Cash and cash equivalents	35,243
Restricted cash	180
Bridge loan, net	311,630
Real estate investment, net	61,346
Common stock investment, at fair value	58,789
Accrued interest and dividends	10,231
CMBS structured pass-through certificates, at fair value	68,133
Accounts receivable and other assets	1,710
Assets, Fair Value Disclosure, Total	8,021,455
Secured financing agreements, net	699,816
Master repurchase agreements	296,991
Unsecured notes, net	202,695
Mortgages payable, net	32,188
Accounts payable and other accrued liabilities	6,492
Accrued interest payable	7,696
Liabilities, Fair Value Disclosure, Total	7,512,806
Fair Value, Recurring [Member] | Reported Value Measurement [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Bonds payable held in variable interest entities, at fair value	6,266,928
Fair Value, Recurring [Member] | Reported Value Measurement [Member] | Bridge Loan [Member]
Bridge loan, net	13,433
Fair Value, Recurring [Member] | Reported Value Measurement [Member] | Mortgages [Member]
Bridge loan, net	744,525
Fair Value, Recurring [Member] | Reported Value Measurement [Member] | Mortgages [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Bridge loan, net	$ 6,716,235