EQUITY METHOD INVESTMENTS (Details) - USD ($) $ in Thousands					1 Months Ended	12 Months Ended
	Oct. 30, 2017	Sep. 13, 2017	Apr. 18, 2017	Apr. 10, 2017	Jun. 30, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity Method Investments
Gain recognized by Company on issuance of shares						$ 41,652
Income (loss) from equity method investments						8,341	$ 5,076	$ 4,476
Return of capital from equity method investments							11	254
Moelis Australia Holdings
Equity Method Investments
Gain recognized by Company on issuance of shares	$ 9,680	$ 14,429		$ 15,170
Income (loss) from equity method investments				$ (2,400)		8,366	3,383	308
Return of capital from equity method investments			$ 11,672
Shares issued	10,060,000	11,940,000
Gain recognized by Company on issuance of shares related to acquisitions						2,372
Summary financial information related to Moelis Australia
Total revenues						83,602	41,292	31,076
Total expenses						(62,187)	(34,526)	(30,460)
Net income (loss)						21,415	6,766	$ 616
Total assets						222,514	53,004
Total liabilities						(54,100)	(29,408)
Net equity						$ 168,414	$ 23,596
Ownership percentage (as a percent)						33.00%	50.00%	50.00%
Entity controlled by Moelis Asset Management LP
Equity Method Investments
Income (loss) from equity method investments							$ 1,693	$ 4,168
Summary financial information related to Moelis Australia
Cash contribution made					$ 265
Cash distributions							$ 1,427	$ 4,669