Summary of Unaudited Quarterly Results of Operations - Summary of Unaudited Quarterly Results of Operations (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues and other income	$ 32,472,818	$ 16,234,830	$ 16,218,225	$ 23,208,975	$ 15,899,246	$ 14,855,912	$ 27,376,050	$ 14,927,956
Income from continuing operations	15,647,453	3,545,483	4,109,400	7,360,515	5,623,293	4,622,874	11,005,829	2,531,688	$ 30,662,851	$ 23,783,684	$ 22,884,825
Net income - America First Multifamily Investors, L.P.	$ 15,647,453	$ 3,545,483	$ 4,109,400	$ 7,360,515	$ 5,623,335	$ 4,623,542	$ 11,005,930	$ 2,531,700
Income from continuing operations, per Unit	$ 0.23	$ 0.05	$ 0.06	$ 0.10	$ 0.09	$ 0.06	$ 0.15	$ 0.04	$ 0.44	$ 0.34	$ 0.34
Net income, basic and diluted, per Unit	$ 0.23	$ 0.05	$ 0.06	$ 0.10	$ 0.09	$ 0.06	$ 0.15	$ 0.04	$ 0.44	$ 0.34	$ 0.34