SUBSEQUENT EVENTS (Details)			1 Months Ended		3 Months Ended		6 Months Ended	9 Months Ended	132 Months Ended	142 Months Ended
	Oct. 02, 2019 USD ($) item	Aug. 31, 2007 shares	Nov. 06, 2019 USD ($) $ / item shares	Sep. 30, 2007 shares	Mar. 31, 2019 shares	Dec. 31, 2007 shares	Jun. 30, 2019 shares	Sep. 30, 2019 USD ($) shares	Dec. 31, 2018 shares	Jun. 30, 2019 USD ($) $ / item	Nov. 01, 2019 USD ($)	Sep. 30, 2018 property
Subsequent events
Number of units | property												913
Number of depository receipts repurchased | shares		1,418,234		1,418,234		1,418,234	1,418,234		1,418,234
Repurchase price of depository receipts (in dollars per receipt) | $ / item										28.20
Total cost of repurchase								$ 3,680,570		$ 43,954,000
Units required to be repurchased (in shares) | shares								2,205
Subsequent event
Subsequent events
Number of depository receipts repurchased | shares			1,879
Repurchase price of depository receipts (in dollars per receipt) | $ / item			59.98
Price per unit of depository receipts | $ / item			1,769.40
Total cost of repurchase			$ 110,860
Subsequent event | 57 Mill Street
Subsequent events
Number of units | item	181
Aggregate purchase price	$ 59,550,000
Termination period	45 days
Purchase deposit	$ 600,000
Interest rate lock deposit											$ 630,000
Mortgage amount											$ 31,000,000
Class B
Subsequent events
Number of depository receipts repurchased | shares		3,491		3,491	3,491				3,491
Total cost of repurchase								$ 699,259
Class B | Subsequent event
Subsequent events
Units required to be repurchased (in shares) | shares			15
Value of units required to be repurchased			$ 26,320
General Partnership
Subsequent events
Number of depository receipts repurchased | shares		184		184	184				184
Total cost of repurchase								36,803
Value of units required to be repurchased								$ 36,803
General Partnership | Subsequent event
Subsequent events
Units required to be repurchased (in shares) | shares			1
Value of units required to be repurchased			$ 1,018