RESTRUCTURING AND OTHER CHARGES (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2019	Apr. 12, 2019
Restructuring costs and reserve
Restructuring charges					$ 118.1
Asset impairment charges					52.0
Epsilon | Discontinued Operations, Held-for-sale
Restructuring costs and reserve
Consideration						$ 4,400.0
Termination Benefits
Restructuring costs and reserve
Restructuring charges					53.5
Asset Impairments
Restructuring costs and reserve
Restructuring charges					52.0
Lease Termination Costs
Restructuring costs and reserve
Restructuring charges					9.1
Other Exit Costs
Restructuring costs and reserve
Restructuring charges					3.5
Corporate/Other
Restructuring costs and reserve
Restructuring charges					37.9
Corporate/Other | Termination Benefits
Restructuring costs and reserve
Restructuring charges	$ 4.0	$ 3.3	$ 11.3		18.6
Corporate/Other | Asset Impairments
Restructuring costs and reserve
Restructuring charges			$ 11.1		11.1
Corporate/Other | Lease Termination Costs
Restructuring costs and reserve
Restructuring charges	7.0				7.0
Corporate/Other | Other Exit Costs
Restructuring costs and reserve
Restructuring charges	1.2				1.2
Corporate/Other | General and administrative
Restructuring costs and reserve
Restructuring charges					37.9
LoyaltyOne
Restructuring costs and reserve
Restructuring charges					50.8
LoyaltyOne | Termination Benefits
Restructuring costs and reserve
Restructuring charges		8.1			7.6
Decrease in restructuring accrual	1.7
LoyaltyOne | Asset Impairments
Restructuring costs and reserve
Restructuring charges	2.6	33.5			40.7
LoyaltyOne | Lease Termination Costs
Restructuring costs and reserve
Restructuring charges		0.2			0.2
LoyaltyOne | Other Exit Costs
Restructuring costs and reserve
Restructuring charges					2.3
LoyaltyOne | Contract Termination
Restructuring costs and reserve
Restructuring charges		0.2
LoyaltyOne | Brand Loyalty
Restructuring costs and reserve
Restructuring charges				$ 7.9
LoyaltyOne | Brand Loyalty | Termination Benefits
Restructuring costs and reserve
Restructuring charges				1.2
LoyaltyOne | Brand Loyalty | Inventory Impairment
Restructuring costs and reserve
Restructuring charges				3.4
LoyaltyOne | Brand Loyalty | Contract Termination
Restructuring costs and reserve
Restructuring charges				2.1
LoyaltyOne | Brand Loyalty | Fixed Asset Impairment
Restructuring costs and reserve
Restructuring charges				$ 1.2
Card Services
Restructuring costs and reserve
Restructuring charges					29.4
Card Services | Termination Benefits
Restructuring costs and reserve
Restructuring charges	$ 27.3				27.3
Card Services | Asset Impairments
Restructuring costs and reserve
Restructuring charges		$ 0.2			0.2
Card Services | Lease Termination Costs
Restructuring costs and reserve
Restructuring charges					$ 1.9