INTANGIBLE ASSETS - Schedule of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Identifiable intangible assets [Abstract]
Gross carrying amount	$ 305,871	$ 260,370
Accumulated amortization	166,102	154,385
Customer relationships & lists
Identifiable intangible assets [Abstract]
Gross carrying amount	234,252	192,185
Accumulated amortization	$ 130,598	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	$ 39,681	39,934
Accumulated amortization	$ 18,315	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	$ 13,338	13,338
Accumulated amortization	$ 9,840	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	$ 18,600	14,913
Accumulated amortization	$ 7,349	$ 6,481
Other | Minimum
Identifiable intangible assets [Abstract]
Amortization period	3 years
Other | Maximum
Identifiable intangible assets [Abstract]
Amortization period	18 years