Restructuring - Restructuring Charges By Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 11.5	$ 7.4	$ 21.5	$ 11.2
Restructuring and Related Cost, Cost Incurred to Date	130.6		130.6
Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	11.5	7.3	21.5	11.1
Eurasia Banking
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	54.9		54.9
Eurasia Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	5.8	1.3	8.1	2.8
Americas Banking
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	11.6		11.6
Americas Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.7	0.2	1.1	0.6
Americas Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.0	0.1	0.0	0.1
Retail
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	31.0		31.0
Retail | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	3.4	2.8	8.8	3.6
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	33.1		33.1
Corporate | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	1.6	$ 3.0	3.5	$ 4.1
DN Now [Member] | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	130.5		130.5
DN Now [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.1		0.1
DN Now [Member] | Eurasia Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	54.9		54.9
DN Now [Member] | Eurasia Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.0		0.0
DN Now [Member] | Americas Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	11.5		11.5
DN Now [Member] | Americas Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.1		0.1
DN Now [Member] | Retail | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	31.0		31.0
DN Now [Member] | Retail | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.0		0.0
DN Now [Member] | Corporate | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	33.1		33.1
DN Now [Member] | Corporate | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	$ 0.0		$ 0.0