PROPERTY, EQUIPMENT AND SOFTWARE, NET - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Long-lived asset impairment	$ 22,351	$ 0	$ 0
Amortization of internally-developed software	58,800	56,600	53,900
Amortization of right-of-use assets	6,737	$ 18,922	$ 30,200
Portion of Restructuring and Related Charges
Property, Plant and Equipment [Line Items]
Long-lived asset impairment	5,600
Restructuring and related charges
Property, Plant and Equipment [Line Items]
Long-lived asset impairment	21,600
Leasehold improvements
Property, Plant and Equipment [Line Items]
Long-lived asset impairment	8,419
Portion of Long-Lived Asset Impairment
Property, Plant and Equipment [Line Items]
Long-lived asset impairment	9,600
Long-Lived Asset Impairment
Property, Plant and Equipment [Line Items]
Long-lived asset impairment	$ 22,400