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RELATED-PARTY TRANSACTIONS (Details) $ in Thousands			3 Months Ended		6 Months Ended		12 Months Ended
RELATED-PARTY TRANSACTIONS (Details) $ in Thousands	Aug. 30, 2014 item	Apr. 15, 2014	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Related-party transactions
Aircraft operating expenses				$ 0		$ 401
Principal repayments						831
Investment into the entity controlled by a related party			$ 19,381		$ 19,381		$ 17,416
Income (loss) from equity method investments			195	(2,851)	3,060	(4,071)
Cash contribution made						4,445
Aircraft lease entered into during August 2014
Related-party transactions
Number of lessees of aircraft (other than the Company), including related party \| item	2
Manager
Related-party transactions
Expenses				154		154
Manager \| Aircraft lease entered into during April 2014
Related-party transactions
Aircraft lease term		10 years
Manager \| Aircraft lease entered into during August 2014
Related-party transactions
Expenses			312		624
Number of lessess of aircraft who are a related party \| item	1
Employees \| Unsecured promissory notes
Related-party transactions
Unsecured promissory notes from employees			119		$ 119		$ 119
Interest rates (as a percent)					4.00%		4.00%
Principal repayments					$ 0	831
Interest income recognized					2	4
Old Holdings \| Expense allocation of occupancy expenses
Related-party transactions
Expenses						2,316
Old Holdings \| Expense allocation of communication, technology and information service expense
Related-party transactions
Expenses						2,745
Moelis Australia Holdings
Related-party transactions
Due from related party							$ 945
Due to related party			88		88
Moelis Asset Management LP
Related-party transactions
Fee for services			399		845
Due from related party			0		0		$ 79
Investment into the entity controlled by a related party				265		265
Income (loss) from equity method investments			228		2,781
Revenue from Related Parties			$ 3,594	$ 948	4,336	$ 948
Cash distributions					$ 1,094