INTANGIBLE ASSETS AND GOODWILL - Finite Lived Assets and Indefinite Lived Assets (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Schedule of Finite and Indefinite-lived Intangible Assets
Finite lived assets, gross	$ 577.4	$ 603.4
Accumulated Amortization	(448.7)	(451.3)
Finite lived assets, net	128.7	152.1
Total Intangible Assets
Gross Assets	578.6	604.6
Accumulated Amortization	(448.7)	(451.3)
Net	129.9	153.3
Tradenames
Indefinite Lived Assets
Indefinite lived assets	1.2	1.2
Customer contracts and lists
Schedule of Finite and Indefinite-lived Intangible Assets
Finite lived assets, gross	319.9	325.1
Accumulated Amortization	(285.6)	(278.7)
Finite lived assets, net	$ 34.3	$ 46.4
Amortization Life and Method
Useful life	7 years	7 years
Total Intangible Assets
Accumulated Amortization	$ (285.6)	$ (278.7)
Premium on purchased credit card portfolios
Schedule of Finite and Indefinite-lived Intangible Assets
Finite lived assets, gross	176.4	192.6
Accumulated Amortization	(87.8)	(93.2)
Finite lived assets, net	88.6	99.4
Total Intangible Assets
Accumulated Amortization	$ (87.8)	$ (93.2)
Premium on purchased credit card portfolios \| Minimum
Amortization Life and Method
Useful life	1 year	1 year
Premium on purchased credit card portfolios \| Maximum
Amortization Life and Method
Useful life	13 years	13 years
Collector database
Schedule of Finite and Indefinite-lived Intangible Assets
Finite lived assets, gross	$ 49.8	$ 53.9
Accumulated Amortization	(49.0)	(52.9)
Finite lived assets, net	$ 0.8	$ 1.0
Amortization Life and Method
Useful life	5 years	5 years
Total Intangible Assets
Accumulated Amortization	$ (49.0)	$ (52.9)
Tradenames
Schedule of Finite and Indefinite-lived Intangible Assets
Finite lived assets, gross	31.3	31.8
Accumulated Amortization	(26.3)	(26.5)
Finite lived assets, net	5.0	5.3
Total Intangible Assets
Accumulated Amortization	$ (26.3)	$ (26.5)
Tradenames \| Minimum
Amortization Life and Method
Useful life	8 years	8 years
Tradenames \| Maximum
Amortization Life and Method
Useful life	15 years	15 years

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount before accumulated amortization of intangible assets, excluding goodwill.

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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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