Other Assets - Additional Information (Details)	12 Months Ended
Dec. 31, 2017 USD ($)
Vantage at Harlingen [Member] \| Series D [Member]
Other Assets [Line Items]
Additional interest related to redemption of taxable MRB	$ 169,000
Avistar at Chase Hill [Member] \| Series C [Member]
Other Assets [Line Items]
Additional interest related to redemption of taxable MRB	$ 35,000

Realized interest on redemption of taxable mortgage revenue bonds.

No definition available.

Name:	atax_RealizedInterestOnRedemptionOfTaxableMortgageRevenueBonds
Namespace Prefix:	atax_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration