Note 9 - Debt - Summary of Financing Arrangements (Details) - USD ($)		3 Months Ended		12 Months Ended
		Mar. 31, 2022		Dec. 31, 2021	Apr. 20, 2021
Unsecured Debt [Member]
Weighted average interest rate	[1]	7.50%		7.50%
Facility [Member]
Outstanding face amount		$ 1,235,787,000		$ 1,276,530,000
Carrying value		$ 1,231,690,000		$ 1,273,051,000
Weighted average interest rate	[1]	2.86%		2.72%
Weighted average life (Year)	[2]	4 years 4 months 24 days		4 years 9 months 18 days
Facility [Member] | Unsecured Debt [Member]
Outstanding face amount		$ 36,500,000		$ 36,500,000
Carrying value		$ 35,303,000		$ 35,233,000
Weighted average life (Year)	[2]	3 years 7 months 6 days		3 years 9 months 18 days
Collateral [Member]
Collateral outstanding amount		$ 2,871,050,000		$ 2,994,912,000
Amortized cost basis		1,385,749,000		1,510,465,000
Collateral carrying value	[3]	$ 1,410,304,000		$ 1,541,857,000
Collateral weighted average life (Year)	[2]	7 years 4 months 24 days		7 years 7 months 6 days
Master Repurchase Agreements Collateralized By CMBS[Member] | Mizuho [Member]
Outstanding face amount	[4]	$ 296,991,000		$ 286,324,000
Carrying value	[4]	$ 296,991,000		$ 286,324,000
Weighted average interest rate	[1],[4]	2.22%		1.97%
Weighted average life (Year)	[2],[4]	10 days		10 days
Collateral outstanding amount	[4]	$ 2,072,842,000		$ 2,101,790,000
Amortized cost basis	[4]	479,087,000		499,975,000
Collateral carrying value	[3],[4]	$ 503,642,000		$ 531,367,000
Collateral weighted average life (Year)	[2],[4]	7 years 9 months 18 days		8 years
Asset Specific Financing [Member] | Freddie Mac [Member] | Facility [Member]
Outstanding face amount		$ 639,902,000		$ 726,312,000
Carrying value		$ 639,902,000		$ 726,312,000
Weighted average interest rate	[1]	2.36%		2.41%
Weighted average life (Year)	[2]	6 years 1 month 6 days		6 years 6 months
Asset Specific Financing [Member] | Freddie Mac [Member] | Collateral [Member]
Collateral outstanding amount		$ 700,309,000		$ 795,223,000
Amortized cost basis		744,525,000		847,364,000
Collateral carrying value	[3]	$ 744,525,000		$ 847,364,000
Collateral weighted average life (Year)	[2]	6 years 1 month 6 days		6 years 6 months
Mezzanine Loan [Member] | Freddie Mac [Member] | Facility [Member]
Outstanding face amount		$ 59,914,000		$ 59,914,000
Carrying value		$ 59,914,000		$ 59,914,000
Weighted average interest rate	[1]	0.30%		0.30%
Weighted average life (Year)	[2]	8 years 1 month 6 days		8 years 3 months 18 days
Mezzanine Loan [Member] | Freddie Mac [Member] | Collateral [Member]
Collateral outstanding amount		$ 97,899,000		$ 97,899,000
Amortized cost basis		100,791,000		100,857,000
Collateral carrying value	[3]	$ 100,791,000		$ 100,857,000
Collateral weighted average life (Year)	[2]	8 years 1 month 6 days		8 years 3 months 18 days
Multifamily Property Debt [Member]
Outstanding face amount		$ 32,480,000		$ 32,480,000
Carrying value		$ 32,188,000		$ 32,176,000
Weighted average interest rate		3.00%	[1]	2.76%
Weighted average life (Year)		6 years 2 months 12 days	[2]	6 years 4 months 24 days
Amortized cost basis		$ 61,346,000		$ 62,269,000
Collateral carrying value		$ 61,346,000	[3]	$ 62,269,000
Collateral weighted average life (Year)		6 years 2 months 12 days	[2]	6 years 4 months 24 days
The 5.75 Percent Senior Notes Due 2026 [Member] | Unsecured Debt [Member]
Outstanding face amount					$ 75,000,000.0
Weighted average interest rate	[1]	5.75%
The 5.75 Percent Senior Notes Due 2026 [Member] | Facility [Member] | Unsecured Debt [Member]
Outstanding face amount		$ 170,000,000		$ 135,000,000
Carrying value		$ 167,392,000		$ 133,092,000
Weighted average life (Year)		4 years	[2]	5 years 9 months
Collateral outstanding amount				$ 4,300

[1] Weighted-average interest rate using unpaid principal balances.

[2] Weighted-average life is determined using the maximum maturity date of the corresponding loans, assuming all extension options are exercised by the borrower.

[3] CMBS are shown at fair value on an unconsolidated basis. SFR Loans and mezzanine loans are shown at amortized cost.

[4] On April 15, 2020, three of our subsidiaries entered into a master repurchase agreement with Mizuho Securities ("Mizuho"). Borrowings under these repurchase agreements are collateralized by portions of the CMBS B-Pieces and CMBS I/O Strips.