BUSINESS CHANGES AND DEVELOPMENTS (Details) $ in Thousands	1 Months Ended		4 Months Ended	5 Months Ended	9 Months Ended
	Nov. 30, 2014	Apr. 30, 2014 USD ($) item shares	Apr. 21, 2014 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) shares	Sep. 30, 2014 USD ($)	Aug. 31, 2014
Reorganization and initial public offering
IPO related proceeds (net of $10,316 of offering costs)						$ 163,682
Proceeds from IPO, net of expenses			$ 500	$ 162,107
Distribution of IPO proceeds to partners						139,429
Tax benefits associated with deferred tax asset payable to partners (as a percent)	85.00%				85.00%
Class A common stock
Reorganization and initial public offering
Number of shares of common stock to be issued upon exchange of a partnership unit | shares		1			1
Class B common stock
Reorganization and initial public offering
Ratio of subscription price to the initial public offering price of shares of common stock		0.00055
Aggregate number of shares of Class B common stock that may be converted into Class A common stock | shares		20,000
Dividends payable ratio to outstanding shares of publicly traded common stock		0.00055
Number of votes entitled to holder for each share of common stock held upon satisfaction of Class B Condition | item		10
Number of votes entitled to holder for each share of common stock held upon failure of Class B Condition | item		1
Moelis Brazil
Reorganization and initial public offering
Ownership percentage (as a percent)							94.00%
Moelis Brazil | Senior bankers
Reorganization and initial public offering
Ownership percentage (as a percent)							6.00%
Group LP
Reorganization and initial public offering
Number of principal classes of units | shares		1
Distribution of IPO proceeds to partners		$ 139,429
Deferred tax assets attributable to exchanges by partners					$ 769
Tax benefits associated with deferred tax asset payable to partners					$ 654
Period of tax receivable agreement					15 years
Group LP | Class A common stock
Reorganization and initial public offering
IPO related proceeds (net of $10,316 of offering costs)						163,682
Proceeds from IPO, net of expenses						$ 162,107
Old Holdings
Reorganization and initial public offering
Pre-offering distribution to partners		195,017
Deferred tax assets attributable to exchanges by partners		$ 60,946
Tax benefits associated with deferred tax asset payable to partners (as a percent)		85.00%
Tax benefits associated with deferred tax asset payable to partners		$ 51,804
Period of tax receivable agreement		15 years