INTANGIBLE ASSETS (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	$ 400,689,000		$ 421,196,000
Impairment of intangible assets, finite-lived	0	$ 0
Acquired database technology [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	104,933,000		105,168,000
Finite-lived intangible assets, accumulated amortization	(91,929,000)		(90,542,000)
Finite-lived intangible assets, net	$ 13,004,000		14,626,000
Weighted-average amortization period	5 years
Acquired customer base [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 484,131,000		487,532,000
Finite-lived intangible assets, accumulated amortization	(243,803,000)		(233,202,000)
Finite-lived intangible assets, net	$ 240,328,000		254,330,000
Weighted-average amortization period	11 years
Acquired trade names and other intangible assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 237,821,000		236,358,000
Finite-lived intangible assets, accumulated amortization	(90,464,000)		(84,118,000)
Finite-lived intangible assets, net	$ 147,357,000		$ 152,240,000
Weighted-average amortization period	12 years