SUBSEQUENT EVENTS (Details)			3 Months Ended	12 Months Ended	115 Months Ended
	Mar. 31, 2017 shares	Aug. 20, 2007 shares	Mar. 31, 2017 shares	Dec. 31, 2016 $ / item	Mar. 31, 2017 $ / item
Subsequent events
Repurchase price of depository receipts (in dollars per receipt) | $ / item					27.14
Number of depository receipts repurchased | shares	1,365,306	1,365,306
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) | $ / item				24.00
Special distribution per depository receipt (in dollars per receipt) | $ / item				0.80
General Partnership
Subsequent events
Repurchases required (in units) | shares			0.2
Number of depository receipts repurchased | shares	162	162
Class B
Subsequent events
Repurchases required (in units) | shares			4.3
Number of depository receipts repurchased | shares	3,072	3,072