BUSINESS CHANGES AND DEVELOPMENTS - Expenses Related to Reorganization and IPO (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2014
Expenses related to the reorganization and IPO
Professional fees expense associated with one-time non-cash acceleration of unvested equity		$ 1,240
Class A common stock
Expenses related to the reorganization and IPO
Compensation and benefits expense associated with issuance of cash and fully vested shares		4,014
Compensation and benefits expense associated with issuance of cash		2,004
Compensation and benefits expense associated with issuance of fully vested shares		2,010
Moelis Australia Holdings
Expenses related to the reorganization and IPO
Expense associated with the one-time non-cash acceleration of unvested equity		4,916
RSUs
Expenses related to the reorganization and IPO
Compensation and benefits expense associated with the amortization of equity awards granted in connection with the IPO		$ 1,167
Vesting period		5 years
Stock options
Expenses related to the reorganization and IPO
Compensation and benefits expense associated with the amortization of equity awards granted in connection with the IPO		$ 3,109
Vesting period		5 years
Managing Directors
Expenses related to the reorganization and IPO
Expense associated with the one-time non-cash acceleration of unvested equity		$ 87,601
Expense associated with the non-cash acceleration of amortization of equity held prior to IPO	$ 10,349