Mortgage Loans - Schedule of loan basis by year of origination (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	$ 1,098,629
7f7 and better
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	412,775
Great Ajax II REIT
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	315,498
CALIFORNIA
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	200,480
4f4-6f6 and below
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	164,455
Originated
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	5,421
Year 2020
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2020 | 7f7 and better
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2020 | Great Ajax II REIT
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2020 | CALIFORNIA
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2020 | 4f4-6f6 and below
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2020 | Originated
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2019
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	788
Year 2019 | 7f7 and better
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2019 | Great Ajax II REIT
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2019 | CALIFORNIA
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2019 | 4f4-6f6 and below
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2019 | Originated
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	788
Year 2018
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	1,489
Year 2018 | 7f7 and better
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	244
Year 2018 | Great Ajax II REIT
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2018 | CALIFORNIA
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2018 | 4f4-6f6 and below
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	0
Year 2018 | Originated
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	1,245
Year 2017
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	3,570
Year 2017 | 7f7 and better
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	124
Year 2017 | Great Ajax II REIT
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	226
Year 2017 | CALIFORNIA
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	351
Year 2017 | 4f4-6f6 and below
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	361
Year 2017 | Originated
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	2,508
Year 2016
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	4,210
Year 2016 | 7f7 and better
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	2,085
Year 2016 | Great Ajax II REIT
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	1,107
Year 2016 | CALIFORNIA
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	216
Year 2016 | 4f4-6f6 and below
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	698
Year 2016 | Originated
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	104
Years 2009-2015
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	101,016
Years 2009-2015 | 7f7 and better
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	33,490
Years 2009-2015 | Great Ajax II REIT
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	34,114
Years 2009-2015 | CALIFORNIA
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	8,291
Years 2009-2015 | 4f4-6f6 and below
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	24,410
Years 2009-2015 | Originated
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	711
Years 2006-2008
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	730,604
Years 2006-2008 | 7f7 and better
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	262,595
Years 2006-2008 | Great Ajax II REIT
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	212,468
Years 2006-2008 | CALIFORNIA
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	155,506
Years 2006-2008 | 4f4-6f6 and below
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	99,980
Years 2006-2008 | Originated
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	55
Years 2005 and prior
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	256,952
Years 2005 and prior | 7f7 and better
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	114,237
Years 2005 and prior | Great Ajax II REIT
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	67,583
Years 2005 and prior | CALIFORNIA
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	36,116
Years 2005 and prior | 4f4-6f6 and below
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	39,006
Years 2005 and prior | Originated
Mortgage Loans [Line Items]
Mortgage loan portfolio by basis	$ 10