INTANGIBLE ASSETS - Summary of Acquired Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 7,253,332	$ 7,253,150
Accumulated Amortization	(5,198,304)	(5,051,149)
Net Carrying Amount	2,055,028	2,202,001
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,113,669	6,113,669
Accumulated Amortization	(4,142,528)	(4,020,282)
Net Carrying Amount	1,971,141	2,093,387
Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,081,083	1,081,083
Accumulated Amortization	(1,012,129)	(988,563)
Net Carrying Amount	68,954	92,520
Other amortizable intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	58,580	58,398
Accumulated Amortization	(43,647)	(42,304)
Net Carrying Amount	$ 14,933	$ 16,094
Minimum | Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	3 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	10 years
Maximum | Other amortizable intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	15 years