The percentage of ownership of available-for-sale securities.

No definition available.

Name:	atax_AvailableForSaleSecuritiesOwnershipPercentage
Namespace Prefix:	atax_
Data Type:	num:percentItemType
Balance Type:	na
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- Definition

Number of Available for Sale Securities, Public Housing Authorities

+ References

No definition available.

+ Details

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Namespace Prefix:	atax_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 8A
-URI http://asc.fasb.org/extlink&oid=82896770&loc=SL6284422-111562

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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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Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtSecurityAxis=atax_LifersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=atax_TrustPortfolioPhcftMember
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PHC Certificates - Additional Information (Details)	12 Months Ended
PHC Certificates - Additional Information (Details)	Dec. 31, 2017 USD ($) Integer	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Impairment charge	$ 761,960
Public Housing Capital Fund Trust I [Member]
Schedule Of Available For Sale Securities [Line Items]
Impairment charge	$ 762,000	$ 0	$ 0
LIFERS [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Securities, Ownership Percentage	100.00%
Public housing capital fund trusts [Member]
Schedule Of Available For Sale Securities [Line Items]
Number of Available for Sale Securities, Public Housing Authorities \| Integer	3