INTANGIBLE ASSETS - Summary of Acquired Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 7,151,788	$ 7,075,611
Accumulated Amortization	(3,670,679)	(2,882,787)
Net Carrying Amount	3,481,109	4,192,824
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,017,524	5,970,884
Accumulated Amortization	(2,843,561)	(2,162,110)
Net Carrying Amount	3,173,963	3,808,774
Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,081,083	1,067,083
Accumulated Amortization	(798,484)	(701,998)
Net Carrying Amount	282,599	365,085
Other amortizable intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	53,181	37,644
Accumulated Amortization	(28,634)	(18,679)
Net Carrying Amount	$ 24,547	$ 18,965
Minimum | Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	8 years
Minimum | Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	2 years
Minimum | Other amortizable intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	1 year
Maximum | Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	18 years
Maximum | Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	5 years
Maximum | Other amortizable intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	15 years