SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment	$ 498,847	$ 497,909
Less: accumulated depreciation and amortization	(270,546)	(267,583)
Net property and equipment	228,301	230,326
Furniture, fixtures, and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	$ 272,733	277,014
Furniture, fixtures, and equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful Lives (in years)	3 years
Furniture, fixtures, and equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful Lives (in years)	12 years
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment	$ 130,959	130,712
Buildings | Minimum
Property, Plant and Equipment [Line Items]
Useful Lives (in years)	3 years
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Useful Lives (in years)	30 years
Corporate aircraft
Property, Plant and Equipment [Line Items]
Useful Lives (in years)	10 years
Property and equipment	$ 11,337	11,334
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 58,929	50,616
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Useful Lives (in years)	3 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Useful Lives (in years)	15 years
Land
Property, Plant and Equipment [Line Items]
Property and equipment	$ 23,648	23,658
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment	$ 1,241	$ 4,575