| Document and Entity Information | Sep. 24, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 24, 2020 |
| Entity Registrant Name | AMERICA FIRST MULTIFAMILY INVESTORS, L.P. |
| Entity Central Index Key | 0001059142 |
| Entity Emerging Growth Company | false |
| Entity File Number | 000-24843 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 47-0810385 |
| Entity Address, Address Line One | 14301 FNB Parkway |
| Entity Address, Address Line Two | Suite 211 |
| Entity Address, City or Town | Omaha |
| Entity Address, State or Province | NE |
| Entity Address, Postal Zip Code | 68154 |
| City Area Code | 402 |
| Local Phone Number | 952-1235 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Security 12b Title | Beneficial Unit Certificates representing assignments of limited partnership interests in America First Multifamily Investors, L.P. |
| Trading Symbol | ATAX |
| Security Exchange Name | NASDAQ |
