Investments in Mortgage Revenue Bonds ("MRBs") - Schedule of MRBs Redeemed (Details) - Mortgage Revenue Bonds [Member]	3 Months Ended
Mar. 31, 2018 USD ($) Unit
Schedule Of Available For Sale Securities [Line Items]
Principal Outstanding at Date of Redemption	$ 10,447,000
Sycamore Walk [Member] \| Series B [Member] \| Bakersfield, California [Member]
Schedule Of Available For Sale Securities [Line Items]
Month Redeemed	January
Units \| Unit	112
Original Maturity Date	Jan. 01, 2018
Base Interest Rate	8.00%
Principal Outstanding at Date of Redemption	$ 1,815,000
Seasons Lakewood [Member] \| Series B [Member] \| Lakewood, California [Member]
Schedule Of Available For Sale Securities [Line Items]
Month Redeemed	March
Units \| Unit	85
Original Maturity Date	Jan. 01, 2019
Base Interest Rate	8.00%
Principal Outstanding at Date of Redemption	$ 5,260,000
Summerhill [Member] \| Series B [Member] \| Bakersfield, California [Member]
Schedule Of Available For Sale Securities [Line Items]
Month Redeemed	March
Units \| Unit	128
Original Maturity Date	Dec. 01, 2018
Base Interest Rate	8.00%
Principal Outstanding at Date of Redemption	$ 3,372,000

Investment owned, redemption month.

No definition available.

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Namespace Prefix:	atax_
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Balance Type:	na
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- Definition

Mortgage loans on real estate, redemption, face amount.

+ References

No definition available.

+ Details

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

- 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

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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

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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

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
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

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- Details

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- Details

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Data Type:	na
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- Details

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- Details

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- Details

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- Details

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