Mortgage Loans - Narrative (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2020 USD ($) numberOfLoanPools loan payment		Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($)
Mortgage Loans on Real Estate
Mortgage loans, net	[1],[2]	$ 1,098,629		$ 1,151,469
Financing Receivable, Allowance for Credit Loss		(16,136)		(1,960)	$ (1,318)	$ (1,164)
Current period additions to allowance account		1,898			0
Interest income		19,600			26,400
Aggregate unpaid principal balance of mortgage loans on real estate		26,200		176,900
Provision for credit losses		(2,122)			(154)
Estimated Market Value Of Underlying Collaterals		44,200
Loan purchase price		$ 25,400
Number of loan pools | numberOfLoanPools		4
Number of Recent Payments Made on RPL Mortgage Loans | payment		7
Loss on sale of mortgage loans		$ (705)			$ 0
Number of sold loans | loan		26			0
RPLs, NPLs, and Originated SBCs [Member]
Mortgage Loans on Real Estate
Mortgage loans, net		$ 1,100,000	[2]	1,200,000
Mortgages purchased
Mortgage Loans on Real Estate
Mortgage loans, net		26,100
SBC loans acquired at or near origination
Mortgage Loans on Real Estate
Mortgage loans, net		$ 4,212		23,434
Number of originated SBC loans acquired | loan		0			19
Aggregate unpaid principal balance of mortgage loans on real estate					$ 17,800
SBC
Mortgage Loans on Real Estate
Mortgage loans, net		$ 5		11,652
7f7 and better
Mortgage Loans on Real Estate
Mortgage loans, net		$ 412,776		419,378
Number of Recent Payments Made on RPL Mortgage Loans | numberOfLoanPools		7
Great Ajax II REIT
Mortgage Loans on Real Estate
Mortgage loans, net		$ 315,497		216,476
4f4-6f6 and below
Mortgage Loans on Real Estate
Mortgage loans, net		$ 164,456		170,318
Number of Recent Payments Made on RPL Mortgage Loans | numberOfLoanPools		4
Originated
Mortgage Loans on Real Estate
Mortgage loans, net		$ 5,420		23,434
Number of loan pools | numberOfLoanPools		1
Residential RPL loan pools
Mortgage Loans on Real Estate
Mortgage loans, net		$ 1,066,555		1,085,514
Number of mortgage loans on real estate | loan		26			38
Aggregate unpaid principal balance of mortgage loans on real estate		$ 2,000			$ 8,500
Mortgage Loans On Real Estate Commitments To Purchase Number | loan		26			38
Nonperforming loan pools
Mortgage Loans on Real Estate
Mortgage loans, net		$ 27,857		$ 30,869
Number of mortgage loans on real estate | loan		1			0
Aggregate unpaid principal balance of mortgage loans on real estate		$ 200
Mortgage Loans On Real Estate Commitments To Purchase Number | loan		1			0

[1] As of March 31, 2020, balances for Mortgage loans, net includes $316.5 million and Secured borrowings, net of deferred costs includes $271.6 million from the 50% and 63% owned joint ventures, respectively. As of December 31, 2019, balances for Mortgage loans, net include $341.8 million and Secured borrowings, net of deferred costs includes $284.8 million from a 50% and 63% owned joint ventures, all of which the Company consolidates under U.S. Generally Accepted Accounting Principles ("U.S. GAAP").

[2] Mortgage loans net include $888.2 million and $908.6 million of loans at March 31, 2020 and December 31, 2019, 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, net include $16.1 million and $2.0 million of allowance for loan credit losses at March 31, 2020 and December 31, 2019, respectively.