GOODWILL AND OTHER INTANGIBLE ASSETS - Other Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Cost	$ 692,577	$ 695,616
Accumulated Amortization	463,619	416,429
Net Book Value	228,958	279,187
Contract rights under placement fee agreements
Finite-Lived Intangible Assets [Line Items]
Cost	60,497	58,516
Accumulated Amortization	25,777	20,888
Net Book Value	$ 34,720	37,628
Contract rights under placement fee agreements | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	3 years
Contract rights under placement fee agreements | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	7 years
Customer contracts
Finite-Lived Intangible Assets [Line Items]
Cost	$ 71,975	71,975
Accumulated Amortization	53,174	49,477
Net Book Value	$ 18,801	22,498
Customer contracts | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	3 years
Customer contracts | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	14 years
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Cost	$ 231,100	231,100
Accumulated Amortization	121,308	105,584
Net Book Value	$ 109,792	125,516
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	3 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	7 years
Developed technology and software
Finite-Lived Intangible Assets [Line Items]
Cost	$ 309,323	314,343
Accumulated Amortization	245,942	224,274
Net Book Value	$ 63,381	90,069
Developed technology and software | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	1 year
Developed technology and software | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	6 years
Patents, trademarks, and other
Finite-Lived Intangible Assets [Line Items]
Cost	$ 19,682	19,682
Accumulated Amortization	17,418	16,206
Net Book Value	$ 2,264	$ 3,476
Patents, trademarks, and other | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	2 years
Patents, trademarks, and other | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	18 years