Interest income earned upon redemption of an Available-for-Sale security.

No definition available.

Name:	atax_ContingentInterestIncome
Namespace Prefix:	atax_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Property loan maximum capacity amount.

+ References

No definition available.

+ Details

Name:	atax_PropertyLoanMaximumCapacityAmount
Namespace Prefix:	atax_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Property loan stated maturity date.

+ References

No definition available.

+ Details

Name:	atax_PropertyLoanStatedMaturityDate
Namespace Prefix:	atax_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Property loans, net of loan loss allowance.

+ References

No definition available.

+ Details

Name:	atax_PropertyLoansNetOfLoanLossAllowanceLineItems
Namespace Prefix:	atax_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118939409&loc=d3e18794-111554

+ Details

Name:	us-gaap_LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Interest received on loans and other debt instruments during the current period.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 16
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3337-108585

+ Details

Name:	us-gaap_ProceedsFromInterestReceived
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow from repayments of the balance excluding interest (principal) on loans receivable and leases held for investment purposes.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromPrincipalRepaymentsOnLoansAndLeasesHeldForInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atax_OhioPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atax_Live929ApartmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atax_VantageAtBrooksLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atax_LakeForestMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Property Loans, Net of Loan Loss Allowances - Additional Information (Details) - USD ($)	1 Months Ended			3 Months Ended		9 Months Ended
	Aug. 31, 2019	Jan. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Property Loans Net Of Loan Loss Allowance [Line Items]
Contingent Interest				$ 3,360	$ 4,246,094	$ 3,045,462	$ 4,246,094
Ohio Properties [Member]
Property Loans Net Of Loan Loss Allowance [Line Items]
Interest earned on property loan principal				$ 983,000	$ 983,000	$ 983,000	$ 983,000
Live 929 Apartments [Member]
Property Loans Net Of Loan Loss Allowance [Line Items]
Total property loan amount	$ 1,000,000
Property loan stated maturity date	Jul. 31, 2049
Vantage at Brooks LLC [Member]
Property Loans Net Of Loan Loss Allowance [Line Items]
Contingent Interest		$ 3,000,000
Lake Forest [Member]
Property Loans Net Of Loan Loss Allowance [Line Items]
Principal received from property loans			$ 5,100,000
Interest received from property loans			$ 4,600,000