Note 4 - CMBS Trusts - Schedule of Geographies and Property Types of Collateral Underlying the CMBS Trusts as Percentage of Collateral Unpaid Principal Balance (Details) - Variable Interest Entity, Primary Beneficiary [Member]	Mar. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Percentage of Collateral Unpaid Principal Balance	100.00%	100.00%	100.00%
Multifamily [Member]
Percentage of Collateral Unpaid Principal Balance	98.38%		98.42%
Manufactured Housing [Member]
Percentage of Collateral Unpaid Principal Balance	1.62%		1.58%
TEXAS
Percentage of Collateral Unpaid Principal Balance	16.60%	16.88%
FLORIDA
Percentage of Collateral Unpaid Principal Balance	14.04%	14.77%
ARIZONA
Percentage of Collateral Unpaid Principal Balance	10.15%	10.37%
CALIFORNIA
Percentage of Collateral Unpaid Principal Balance	8.75%	8.50%
GEORGIA
Percentage of Collateral Unpaid Principal Balance	5.11%	4.97%
WASHINGTON
Percentage of Collateral Unpaid Principal Balance	6.36%	6.19%
NEW JERSEY
Percentage of Collateral Unpaid Principal Balance	4.79%	4.65%
NEVADA
Percentage of Collateral Unpaid Principal Balance	3.61%	3.51%
COLORADO
Percentage of Collateral Unpaid Principal Balance	4.19%	4.08%
CONNECTICUT
Percentage of Collateral Unpaid Principal Balance	3.11%
NORTH CAROLINA
Percentage of Collateral Unpaid Principal Balance	3.21%	3.12%
NEW YORK
Percentage of Collateral Unpaid Principal Balance	2.14%	2.45%
OHIO
Percentage of Collateral Unpaid Principal Balance	1.77%	1.72%
VIRGINIA
Percentage of Collateral Unpaid Principal Balance	1.75%	1.70%
INDIANA
Percentage of Collateral Unpaid Principal Balance	1.73%	1.68%
SOUTH CAROLINA
Percentage of Collateral Unpaid Principal Balance	1.60%	1.56%
MARYLAND
Percentage of Collateral Unpaid Principal Balance	1.60%	1.55%
MISSOURI
Percentage of Collateral Unpaid Principal Balance	1.30%	1.26%
Other [Member]
Percentage of Collateral Unpaid Principal Balance	8.19%	8.02%