Other Assets - Summary of the Terms of the Taxable MRBs Redeemed (Details)	12 Months Ended
Dec. 31, 2017 USD ($) Unit	Dec. 31, 2016 USD ($) Unit
Vantage at Harlingen [Member] \| Series C [Member] \| San Antonio, Texas [Member]
Other Assets [Line Items]
Units (Unaudited) \| Unit	288
Maturity Date	Oct. 01, 2053
Base Interest Rate	9.00%
Principal Outstanding at Date of Redemption \| $	$ 1,278,117
Avistar at Chase Hill [Member] \| Series D [Member] \| San Antonio, Texas [Member]
Other Assets [Line Items]
Units (Unaudited) \| Unit	232
Maturity Date	Apr. 01, 2050
Base Interest Rate	9.00%
Principal Outstanding at Date of Redemption \| $	$ 232,145
Silver Moon [Member] \| Series B [Member] \| Albuquerque New Mexico
Other Assets [Line Items]
Units (Unaudited) \| Unit		151
Maturity Date		Aug. 01, 2055
Base Interest Rate		12.00%
Principal Outstanding at Date of Redemption \| $		$ 499,461

Mortgage loans on real estate, redemption, face amount.

No definition available.

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

- Definition

Other assets.

+ References

No definition available.

+ Details

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

- Definition

Stated maturity date of the mortgage loan receivable on real estate, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

+ Details

Name:	us-gaap_MortgageLoanOnRealEstateFinalMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The stated interest rate on the mortgage loan receivable or the weighted average interest rate on a group of loans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

+ Details

Name:	us-gaap_MortgageLoansOnRealEstateInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of units in a real estate property owned as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfUnitsInRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atax_VantageAtHarlingenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis=atax_FourthMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=atax_SanAntonioTexasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atax_AvistarAtChaseHillMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis=atax_ThirdMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atax_SilverMoonMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis=us-gaap_SecondMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=atax_AlbuquerqueNewMexicoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: