Mortgage Loans - Narrative (Details)		1 Months Ended	3 Months Ended		12 Months Ended
		Feb. 28, 2023 USD ($) residential_rpl	Mar. 31, 2024 USD ($) loan payment loanPool	Mar. 31, 2023 USD ($) loan	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Mortgage Loans on Real Estate
Mortgage loans held-for-investment, net	[1],[2]		$ 438,698,000		$ 864,551,000
Financing receivable, adjustment, lower of cost or market			$ (47,300,000)		(8,600,000)
Number of loans classified to mortgage loan held-for sale | loan			2,109
Allowance for loan credit losses			$ 403,000	$ 4,338,000	3,426,000	$ 6,107,000
(Increase in)/reversal of allowance for expected credit losses due to (decreases)/increases in the net present value of expected cash flows			1,112,000	(621,000)
Accretable yield			$ 11,800,000	$ 13,300,000
Number of sold loans | loan			235	0
Gain (loss) on sale of mortgage loans				$ (400,000)
Number of loan pools established | loanPool			3
Number of loan pools | loanPool			6
Gross amount of loans and securities pledged as collateral			$ 447,282,000		541,999,000
Reclassification to non-credit discount from the allowance for changes in payment timing expectations			310,000	1,225,000
Increase in allowance for expected credit losses for loan acquisitions during the period			0	$ (33,000)
RPLs, NPLs, and Originated SBCs
Mortgage Loans on Real Estate
Mortgage loans held-for-investment, net			438,698,000		864,551,000
Mortgage loans held-for-sale			$ 368,300,000		55,700,000
SBC loans acquired at or near origination
Mortgage Loans on Real Estate
Number of originated SBC loans acquired | loan			0	0
Residential RPLs
Mortgage Loans on Real Estate
Mortgage loans held-for-investment, net			$ 427,486,000		787,700,000
Number of mortgage loans on real estate		1	0	3
Unpaid principal balance		$ 200,000		$ 800,000
Number of recent payments made on RPL mortgage loans | payment			7
Gross amount of loans and securities pledged as collateral			$ 50,000
Residential NPLs
Mortgage Loans on Real Estate
Mortgage loans held-for-investment, net			$ 5,813,000		$ 71,075,000
Number of mortgage loans on real estate | loan			0	0

[1] As of March 31, 2024 and December 31, 2023, balances for Mortgage loans held-for-investment, net include $0.2 million and $0.6 million, respectively, from a 50.0% owned joint venture, which the Company consolidates under U.S. Generally Accepted Accounting Principles ("U.S. GAAP" or "GAAP").

[2] Mortgage loans held-for-sale, net and mortgage loans held-for-investment, net include $623.2 million and $628.6 million of loans at March 31, 2024 and December 31, 2023, respectively, transferred to securitization trusts that are variable interest entities (“VIEs”); these loans can only be used to settle obligations of the VIEs. Secured borrowings consist of notes issued by VIEs that can only be settled with the assets and cash flows of the VIEs. The creditors do not have recourse to the primary beneficiary (Great Ajax Corp.). See Note 9 — Debt. Mortgage loans held-for-investment, net include $0.4 million and $3.4 million of allowance for expected credit losses at March 31, 2024 and December 31, 2023, respectively.