Restructuring - Restructuring Charges By Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 17.1	$ 11.5	$ 23.1	$ 21.5
Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	10.3	11.5	10.3	21.5
Severance | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.0	1.6	0.0	3.5
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	6.8		12.8	0.0
Other Restructuring [Member] | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	5.1		10.6	0.0
Eurasia Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	8.8	5.8	8.8	8.1
Eurasia Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.1		0.6	0.0
Americas Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.3	0.7	0.3	1.1
Retail | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	1.2	$ 3.4	1.2	8.8
Retail | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	1.6		1.6	$ 0.0
DN Now [Member] | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	195.1		195.1
DN Now [Member] | Severance | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	54.3		54.3
DN Now [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	18.7		18.7
DN Now [Member] | Other Restructuring [Member] | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	12.2		12.2
DN Now [Member] | Eurasia Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	87.7		87.7
DN Now [Member] | Eurasia Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	2.6		2.6
DN Now [Member] | Americas Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	13.2		13.2
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	39.9		39.9
DN Now [Member] | Retail | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	$ 3.8		$ 3.8