DISCONTINUED OPERATIONS (Details) - USD ($) $ in Millions		12 Months Ended
	Jul. 01, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2019	Apr. 12, 2019	Mar. 31, 2019
Disposal Group, Including Discontinued Operation, Additional Disclosures
Long-term Debt		$ 2,849.9
Mandatory payment per credit agreement					$ 500.0
Depreciation and amortization		73.2	$ 293.7	$ 309.7
Capital expenditures		55.8	106.5	107.2
Epsilon
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration, cash associated with disposal group	$ 42.2
Transaction costs		79.0
After tax loss on sale		252.1
Disposal Group, Including Discontinued Operation, Additional Disclosures
Mandatory payment per credit agreement		500.0			$ 500.0		$ 500.0
Epsilon | Senior Notes
Disposal Group, Including Discontinued Operation, Additional Disclosures
Long-term Debt		1,900.0					$ 1,900.0
Epsilon | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration						$ 4,400.0
Pre-tax gain on deconsolidation		512.2
Disposal Group, Including Discontinued Operation, Income Statement Disclosures
Revenue		999.6	2,175.1	2,272.1
Cost of operations (exclusive of depreciation and amortization)		993.9	1,744.4	1,834.8
Depreciation and other amortization		29.7	115.4	109.4
Amortization of purchased intangibles		43.5	178.3	200.3
Interest expense		64.1	128.3	109.0
Gain on sale of Epsilon		(512.2)
Income (loss) before benefit from income taxes		380.6	8.7	18.6
Provision (benefit) from income taxes		675.2	(8.9)	(0.9)
(Loss) income from discontinued operations, net of taxes		$ (294.6)	17.6	$ 19.5
Assets :
Cash and cash equivalents			45.7
Accounts receivable, net			519.9
Other current assets			56.6
Property and equipment, net			306.9
Intangible assets, net			322.3
Goodwill			2,886.2
Other assets			19.8
Total assets of discontinued operations			4,157.4
Liabilities:
Accounts payable			72.2
Accrued expenses			98.8
Other current liabilities			52.5
Other liabilities			36.9
Total liabilities of discontinued operations			$ 260.4
Epsilon | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration	4,451.9
Net carrying value of assets and liabilities (including other comprehensive income)	3,939.7
Pre-tax gain on deconsolidation	512.2
Disposal Group, Including Discontinued Operation, Income Statement Disclosures
Gain on sale of Epsilon	$ (512.2)