INCOME TAXES - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended				36 Months Ended
	Dec. 31, 2016	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Income Tax Contingency [Line Items]
Accrued income taxes	$ 800,000	$ 2,600,000		$ 800,000		$ 2,600,000
Prepaid taxes	13,400,000	12,400,000		13,400,000		12,400,000
Current tax expense (benefit)		2,121,000		4,452,000	$ 11,657,000
Deferred Income tax expense (benefit)		5,591,000		1,868,000	$ 2,900,000
Deferred tax asset relating to capital losses	5,700,000	5,800,000		5,700,000		5,800,000
Deferred tax liabilities	0	(7,134,000)		0		(7,134,000)
Interest and penalties recognized for uncertain tax positions		0				$ 0
Percentage of applicable cash saving in income tax distributable to specified unitholders						85.00%
Percentage of applicable cash saving in income tax available for the entity						15.00%
Amount due pursuant to tax receivable agreement	2,520,000	1,656,000	[1]	2,520,000		$ 1,656,000	[1]
Other assets
Income Tax Contingency [Line Items]
Net deferred tax assets	2,100,000			2,100,000
Deferred tax liabilities		(5,700,000)				(5,700,000)
Accrued Expenses
Income Tax Contingency [Line Items]
Liability for unrecognized tax benefits for uncertain income tax positions	800,000	800,000		800,000		800,000
Amount Payable Pursuant to Tax Receivable Agreement
Income Tax Contingency [Line Items]
Amount due pursuant to tax receivable agreement	2,500,000	1,700,000		2,500,000		1,700,000
Indemnity Counterparty
Income Tax Contingency [Line Items]
Settlements receivable	3,300,000			3,300,000
Amount recovered from indemnity counterparty		3,300,000
State and Local Jurisdiction | New York
Income Tax Contingency [Line Items]
Unincorporated business tax payable (receivable)	400,000	$ 500,000		400,000		$ 500,000
State income tax expense (benefit)	3,300,000			3,300,000
Estimated insurance recovery recorded as other income and fees	3,300,000			3,300,000
State income tax payable	$ 3,300,000			$ 3,300,000

[1] Includes amounts relating to consolidated variable interest entities. See Note 3.