SEGMENT REPORTING (Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenses	$ 227,188	$ 254,127	$ 654,488	$ 1,193,791
Equity compensation expenses	23,940	18,091	67,534	52,097
Ares Management L.P
Segment Reporting, Other Significant Reconciling Item [Line Items]
Acquisition and merger-related expenses	0	0	0	275,177
Due to affiliates	59,456		59,456			$ 39,184
Ares Management L.P | Affiliated entity | ARCC | Rent and other occupancy expenses
Segment Reporting, Other Significant Reconciling Item [Line Items]
Due to affiliates	11,800		11,800		$ 600	2,200	$ 3,000	$ 3,200	$ 2,900
Consolidated Funds
Segment Reporting, Other Significant Reconciling Item [Line Items]
Due to affiliates	0		0			0
Operating segment
Segment Reporting, Other Significant Reconciling Item [Line Items]
Acquisition and merger-related expenses	253	2,878	(19)	258,722
Equity compensation expenses	23,940	18,091	67,534	52,097
Placement fees and underwriting costs	6,194	4,495	9,710	14,317
Amortization of intangibles	1,245	3,651	7,817	14,200
Depreciation expense	4,102	3,468	12,417	9,458
Operating segment | Ares Management L.P
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenses	120,229	149,818	323,261	630,598
Reconciling items
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenses	106,959	104,309	331,227	563,193
Administrative fees	7,084	7,352	20,266	26,090
Acquisition and merger-related expenses	253	2,818	(19)	278,878
Equity compensation expenses	23,940	18,091	67,534	52,097
Placement fees and underwriting costs	6,194	4,495	9,710	14,317
Amortization of intangibles	1,245	3,651	7,817	14,200
Depreciation expense	4,102	3,468	12,417	9,458
Other expenses	0	0	11,836	0
Reconciling items | Non-Controlling interest | Subsidiaries
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenses	814	(217)	2,141	357
Reconciling items | Consolidated Funds
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenses	21,971	25,862	77,982	45,196
Eliminations
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenses	(9,138)	(6,823)	(28,721)	(17,724)
Acquisition and merger-related expenses				0
Eliminations | Ares Management L.P
Segment Reporting, Other Significant Reconciling Item [Line Items]
Due to affiliates	0		0
Eliminations | Consolidated Funds
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenses	(9,138)	(6,823)	(28,721)	(17,724)
Due to affiliates	(7,997)		(7,997)			$ (11,285)
OMG
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenses	$ 50,494	$ 45,612	$ 150,264	$ 140,324