INTANGIBLE ASSETS - Schedule of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Identifiable intangible assets [Abstract]
Gross carrying amount	$ 327,284	$ 323,848
Accumulated amortization	201,102	179,924
Customer relationships & lists
Identifiable intangible assets [Abstract]
Gross carrying amount	241,505	239,578
Accumulated amortization	$ 153,361	139,863
Customer relationships & lists | Minimum
Identifiable intangible assets [Abstract]
Amortization period	10 years
Customer relationships & lists | Maximum
Identifiable intangible assets [Abstract]
Amortization period	20 years
Trademarks & trade names
Identifiable intangible assets [Abstract]
Gross carrying amount	$ 43,154	43,102
Accumulated amortization	$ 23,821	20,477
Trademarks & trade names | Minimum
Identifiable intangible assets [Abstract]
Amortization period	2 years
Trademarks & trade names | Maximum
Identifiable intangible assets [Abstract]
Amortization period	17 years
Developed technology
Identifiable intangible assets [Abstract]
Gross carrying amount	$ 21,394	20,206
Accumulated amortization	$ 13,011	11,008
Developed technology | Minimum
Identifiable intangible assets [Abstract]
Amortization period	5 years
Developed technology | Maximum
Identifiable intangible assets [Abstract]
Amortization period	12 years
Other
Identifiable intangible assets [Abstract]
Gross carrying amount	$ 21,231	20,962
Accumulated amortization	$ 10,909	$ 8,576
Other | Minimum
Identifiable intangible assets [Abstract]
Amortization period	3 years
Other | Maximum
Identifiable intangible assets [Abstract]
Amortization period	18 years