Note 3 - Loans Held for Investment - Geographies and Property Types of Collateral Underlying the Loans Held-for-investment as a Percentage of the Loans' Face Amounts (Details)	Sep. 30, 2021	Dec. 31, 2020
% of loan portfolio	100.00%	100.00%
Single Family Rental [Member]
% of loan portfolio	81.72%	87.30%
Multifamily [Member]
% of loan portfolio	17.98%	12.70%
Life Science [Member]
% of loan portfolio	0.30%	0.00%
GEORGIA
% of loan portfolio	38.78%	39.81%
FLORIDA
% of loan portfolio	22.17%	20.88%
TEXAS
% of loan portfolio	6.83%	7.26%
MARYLAND
% of loan portfolio	5.92%	7.66%
MINNESOTA
% of loan portfolio	5.08%	4.82%
ALABAMA
% of loan portfolio	3.50%	3.59%
CALIFORNIA
% of loan portfolio	2.64%	0.00%
NEW JERSEY
% of loan portfolio		1.98%
NORTH CAROLINA
% of loan portfolio	1.94%	1.67%
MISSOURI
% of loan portfolio	1.25%	1.01%
MISSISSIPPI
% of loan portfolio	1.01%	1.03%
Other [Member]
% of loan portfolio	10.87%	10.29%