GOODWILL AND OTHER INTANGIBLE ASSETS- Intangible assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Amortizing acquired intangible assets
Gross Carry Amount	$ 1,356,641	$ 1,145,700
Accumulated Amortization	(443,531)	(383,505)
Net Book Value	913,110	762,195
Customer relationships
Amortizing acquired intangible assets
Gross Carry Amount	1,209,291	1,008,186
Accumulated Amortization	(404,967)	(349,125)
Net Book Value	804,324	659,061
Management contracts
Amortizing acquired intangible assets
Gross Carry Amount	142,319	133,112
Accumulated Amortization	(35,735)	(31,911)
Net Book Value	106,584	101,201
Other intangibles
Amortizing acquired intangible assets
Gross Carry Amount	5,031	4,402
Accumulated Amortization	(2,829)	(2,469)
Net Book Value	$ 2,202	$ 1,933