CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2021	Dec. 31, 2020
Preferred stock, par value per share (in dollars per share)		$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)		25,000,000	25,000,000
Common stock, par value per share (in dollars per share)		$ 0.01	$ 0.01
Common stock, shares authorized (in shares)		125,000,000	125,000,000
Common stock, shares issued (in shares)		23,140,131	22,978,339
Common stock, shares outstanding (in shares)		23,140,131	22,978,339
Mortgage loans		$ 790,900	$ 842,200
Allowance for loan credit losses		13,876	13,712
Property held-for-sale, valuation allowances		400	1,400
Basis		336,700	273,400
Debt securities accumulated unrealized gain (loss)		3,400	400
Noncontrolling interest	[1]	3,281	29,130
Secured Borrowings
Deferred issuance costs		8,300	5,400
Convertible senior notes
Deferred issuance costs		$ 2,100	$ 3,300
2017-D
Percentage of additional ownership in joint venture obtained		50.00%
2017-D | Great Ajax Corp
Ownership percentage by parent		50.00%	50.00%
2018-C
Percentage of additional ownership in joint venture obtained		37.00%
2018-C | Great Ajax Corp
Ownership percentage by parent		100.00%	63.00%
Investment in AS Ajax E II LLC
Percentage of additional ownership in joint venture obtained		53.10%	53.10%
Investment in AS Ajax E II LLC | Great Ajax Corp
Percentage of additional ownership in joint venture obtained		53.10%	53.10%
Great Ajax II REIT | Great Ajax Corp
Ownership percentage by parent		99.90%	99.90%
Consolidated entities
Mortgage loans		$ 1,500	$ 307,100
Secured borrowings, net			250,600
Noncontrolling interest		1,800	27,400
Consolidated entities | Investment in AS Ajax E II LLC
Noncontrolling interest			1,500
Consolidated entities | Investment in AS Ajax E II LLC | Great Ajax Corp
Noncontrolling interest		1,300
Consolidated entities | Great Ajax II REIT
Noncontrolling interest			$ 200
Consolidated entities | Great Ajax II REIT | Great Ajax Corp
Noncontrolling interest		$ 100
Common stock, par value $0.01 per share
Common stock, shares outstanding (in shares)		23,140,131	22,978,339
Beneficial interests in securitization trusts
Allowance for loan credit losses		$ 600	$ 4,500
Preferred stock - Series A shares
Preferred stock, fixed-to-floating rate cumulative redeemable		7.25%
Preferred stock, liquidation preference per share (in dollars per share)		$ 25.00	$ 25.00
Preferred stock, shares issued (in shares)		2,307,400	2,307,400
Preferred Stock, shares outstanding (in shares)		2,307,400	2,307,400
Preferred stock - Series B shares
Preferred stock, fixed-to-floating rate cumulative redeemable		5.00%
Preferred stock, liquidation preference per share (in dollars per share)		$ 25.00	$ 25.00
Preferred stock, shares issued (in shares)		2,892,600	2,892,600
Preferred Stock, shares outstanding (in shares)		2,892,600	2,892,600

[1] As of September 30, 2021 non-controlling interests includes $1.8 million from a 50.0% owned joint venture, $1.3 million from a 53.1% owned subsidiary and $0.1 million from a 99.9% owned subsidiary. As of December 31, 2020 non-controlling interests includes $27.4 million from the 50.0% and 63.0% owned joint ventures, $1.5 million from a 53.1% owned subsidiary and $0.2 million from a 99.9% owned subsidiary which the Company consolidates under U.S. GAAP.