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RELATED-PARTY TRANSACTIONS (Details) $ in Thousands			1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
RELATED-PARTY TRANSACTIONS (Details) $ in Thousands	Aug. 30, 2014 item	Apr. 15, 2014	Aug. 30, 2014 item	Apr. 14, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 30, 2014 USD ($)
Related-party transactions
Principal repayments								$ 831
Investment into the entity controlled by a related party						$ 20,873	$ 17,459
Income (loss) from equity method investments						5,076	4,476	(2,185)
Aircraft lease entered into during August 2014
Related-party transactions
Number of other lessees \| item			2
Expense allocation of communication, technology and information service expense \| Old Holdings
Related-party transactions
Expenses								2,745
Manager \| Aircraft lease entered into during April 2010
Related-party transactions
Aircraft operating expenses				$ 401
Manager \| Aircraft lease entered into during April 2014
Related-party transactions
Expenses								280
Aircraft lease term		10 years
Manager \| Aircraft lease entered into during August 2014
Related-party transactions
Expenses						1,248	1,248
Mr. Moelis \| Aircraft lease entered into during August 2014
Related-party transactions
Number of lessees of aircraft who are a related party \| item	1
Employees \| Unsecured promissory notes
Related-party transactions
Unsecured promissory notes from employees						$ 922	$ 119
Interest rates (as a percent)						4.00%	4.00%
Principal repayments						$ 0	$ 0	831
Interest income recognized						25	5	6
Old Holdings \| Expense allocation of occupancy expenses
Related-party transactions
Expenses								2,316
Moelis Australia Holdings
Related-party transactions
Due to related party						38	167
Income (loss) from equity method investments						3,383	308	(2,185)
Moelis Asset Management LP
Related-party transactions
Fee for services					$ 1,424	1,283	1,698
Due from related party						0	3
Investment into the entity controlled by a related party									$ 265
Income (loss) from equity method investments						1,693	4,168	0
Cash distributions						1,427	4,669	0
Revenue from related parties						$ 7,281	$ 5,780	$ 5,829
Moelis Asset Management LP \| Aircraft lease entered into during August 2014
Related-party transactions
Number of lessees of aircraft who are a related party \| item	1