Represents value of the investment in debt securities.

No definition available.

Name:	ajx_InvestmentInDebtSecurities
Namespace Prefix:	ajx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of debt securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 2
-Subparagraph (b)-(g)
-URI http://asc.fasb.org/extlink&oid=75019621&loc=d3e62557-112803

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount of the unpaid portion of the fee payable to the managing member or general partner for management of the fund or trust.

+ References

No definition available.

+ Details

Name:	us-gaap_ManagementFeePayable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Receivables to be collected from (obligations owed to) related parties, net as of the balance sheet date where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_CounterpartyNameAxis=ajx_GregoryFundingLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=ajx_ReceivablesFromServicerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_AccountsPayableAndAccruedLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=ajx_ThetisAssetManagementLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=ajx_ManagementFeePayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=ajx_AjaxMortgageLoanTrust2018AMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=ajx_AjaxMortgageLoanTrust2018BMember
Namespace Prefix:
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Balance Type:
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Related Party Transactions - Schedule of Balance Sheet of Related Party Transaction (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2016
Related Party Transaction [Line Items]
Available-for-sale Securities, Debt Securities	$ 146,811
Related Party Transaction, Due from (to) Related Party	14,587	$ 17,005
Investment in debt securities		6,285	$ 6,300
Management fee payable	881	750
Gregory \| Receivable from Servicer
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party	14,587	17,005
Gregory \| Accrued expenses and other liabilities
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party		217
Gregory \| Prepaid expenses and other assets
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party	11
Thetis \| Management fee payable
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party	881	750
Thetis \| Accrued expenses and other liabilities
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party	16
Thetis \| Prepaid expenses and other assets
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party		$ 0
2018-A \| Prepaid expenses and other assets
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party	2
2018-B \| Prepaid expenses and other assets
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party	$ 2