SUBSEQUENT EVENTS (Details)		1 Months Ended	9 Months Ended	109 Months Ended
	Oct. 26, 2016 $ / shares $ / item	Nov. 04, 2016 USD ($) $ / item shares	Sep. 30, 2016 USD ($) shares	Sep. 30, 2016 $ / item shares	Dec. 31, 2015 $ / item	Sep. 30, 2015 $ / item	Jun. 30, 2015 $ / item	Mar. 31, 2015 $ / item
Subsequent events
Repurchase price of depository receipts (in dollars per receipt) | $ / item				26.81
Number of depository receipts repurchased				1,352,427
Quarterly distribution per unit (in dollars per unit) | $ / item					7.50	7.50	7.50	7.50
Quarterly distributions per depositary receipt (in dollars per receipt) | $ / item					0.25	0.25	0.25	0.25
General Partnership
Subsequent events
Value of units required to be repurchased | $			$ 6,783
Repurchases required (in units)			5
Number of depository receipts repurchased				156
Class B
Subsequent events
Value of units required to be repurchased | $			$ 128,874
Repurchases required (in units)			86
Number of depository receipts repurchased				2,970
Subsequent event
Subsequent events
Repurchase of depository receipts | $		$ 20,605
Repurchase price of units (in dollars per unit) | $ / item		1,803.90
Repurchase price of depository receipts (in dollars per receipt) | $ / item		60.13
Number of depository receipts repurchased		330
Quarterly distribution per unit (in dollars per unit) | $ / item	7.50
Quarterly distributions per depositary receipt (in dollars per receipt) | $ / item	0.25
Special distribution per unit (in dollars per unit) | $ / shares	$ 24
Special distribution per depositary receipt (in dollars per receipt) | $ / shares	$ 0.80
Subsequent event | General Partnership
Subsequent events
Value of units required to be repurchased | $		$ 248
Repurchases required (in units)		0.1
Subsequent event | Class B
Subsequent events
Value of units required to be repurchased | $		$ 4,713
Repurchases required (in units)		2.6