INTANGIBLE ASSETS - Schedule of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Identifiable intangible assets [Abstract]
Gross carrying amount	$ 307,176	$ 263,790
Accumulated amortization	172,779	154,385
Customer relationships & lists
Identifiable intangible assets [Abstract]
Gross carrying amount	230,243	192,185
Accumulated amortization	$ 135,158	122,545
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	$ 40,773	39,934
Accumulated amortization	$ 19,408	16,755
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	$ 15,740	13,338
Accumulated amortization	$ 10,429	8,604
Developed technology | Minimum
Identifiable intangible assets [Abstract]
Amortization period	5 years
Developed technology | Maximum
Identifiable intangible assets [Abstract]
Amortization period	10 years
Other
Identifiable intangible assets [Abstract]
Gross carrying amount	$ 20,420	18,333
Accumulated amortization	$ 7,784	$ 6,481
Other | Minimum
Identifiable intangible assets [Abstract]
Amortization period	3 years
Other | Maximum
Identifiable intangible assets [Abstract]
Amortization period	18 years