GOODWILL AND INTANGIBLE ASSETS (Carrying Value of Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-lived intangible assets, net
Intangible assets, gross	$ 109,106	$ 153,739
Foreign currency translation	0	(3,205)
Total intangible assets acquired	109,106	150,534
Less: accumulated amortization	(68,641)	(92,219)
Intangible assets, net	40,465	58,315
Fully-amortized intangibles, amount removed during the period	41,400
General, administrative and other expense
Finite-lived intangible assets, net
Amortization expense	$ 17,900	26,600	$ 46,200
Management contracts
Finite-lived intangible assets, net
Weighted average amortization period	2 years
Intangible assets, gross	$ 67,306	111,939
Client relationships
Finite-lived intangible assets, net
Weighted average amortization period	10 years 6 months
Intangible assets, gross	$ 38,600	38,600
Trade name
Finite-lived intangible assets, net
Weighted average amortization period	4 years 6 months
Intangible assets, gross	$ 3,200	$ 3,200