PROPERTY AND EQUIPMENT, NET (Components of Property and Equipment and Depreciation) (Details) - USD ($) $ in Thousands		12 Months Ended
	Nov. 01, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross		$ 297,314	$ 259,566
Less accumulated depreciation and amortization		(127,781)	(94,307)
Total		169,533	165,259	$ 102,646
Depreciation and amortization expense		50,500	35,400	28,500
Payments to acquire an office building		$ (68,793)	(99,308)	(37,574)
Computer hardware
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		3 years
Property and equipment, gross		$ 117,333	96,286
Buildings
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		46 years
Property and equipment, gross		$ 52,007	51,300
Leasehold improvements
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		7 years
Property and equipment, gross		$ 39,675	30,634
Purchased computer software
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		3 years
Property and equipment, gross		$ 31,993	32,115
Furniture, fixture and other equipment
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		7 years
Property and equipment, gross		$ 31,859	28,193
Office equipment
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		7 years
Property and equipment, gross		$ 20,971	18,901
Land improvements
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		18 years
Property and equipment, gross		$ 2,137	2,137
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross		1,339	0
Assets leased to third parties under operating lease
Property, Plant and Equipment [Line Items]
Property and equipment, gross		6,700	10,700
Less accumulated depreciation and amortization		(200)	(100)
Depreciation and amortization expense		200	100
Belarus
Property, Plant and Equipment [Line Items]
Total		$ 73,988	$ 75,984	$ 50,085
Belarus | Buildings
Property, Plant and Equipment [Line Items]
Payments to acquire an office building	$ (18,900)