Restructuring - Restructuring Charges By Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 13.8	$ 8.6	$ 35.3	$ 19.8
Restructuring and Related Cost, Cost Incurred to Date	144.4		144.4
Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	13.8	8.6	35.3	19.7
Eurasia Banking
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	63.5		63.5
Eurasia Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	8.6	1.3	16.7	4.1
Americas Banking
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	12.3		12.3
Americas Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.7	0.6	1.8	1.2
Americas Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.0	0.0	0.0	0.1
Retail
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	33.0		33.0
Retail | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	2.0	0.9	10.8	4.5
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	35.6		35.6
Corporate | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	2.5	$ 5.8	6.0	$ 9.9
DN Now [Member] | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	144.3		144.3
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	63.5		63.5
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	12.2		12.2
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	33.0		33.0
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	35.6		35.6
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