INVESTMENTS IN OPERATING PARTNERSHIPS - Operating Partnerships (Details)	Sep. 30, 2019	Sep. 30, 2018
Number Of Operating Partnerships [Line Items]
Number Of Operating Partnerships	20	35
Series 15
Number Of Operating Partnerships [Line Items]
Number Of Operating Partnerships	0	8
Series 16
Number Of Operating Partnerships [Line Items]
Number Of Operating Partnerships	8	12
Series 17
Number Of Operating Partnerships [Line Items]
Number Of Operating Partnerships	2	4
Series 18
Number Of Operating Partnerships [Line Items]
Number Of Operating Partnerships	10	10
Series 19
Number Of Operating Partnerships [Line Items]
Number Of Operating Partnerships	0	1