Restructuring - Restructuring Charges By Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 6.0	$ 10.0
Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.0	10.0
Severance | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.0	1.9
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	6.0	0.0
Other Restructuring [Member] | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	5.5	0.0
Eurasia Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.0	2.3
Eurasia Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.5	0.0
Americas Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.0	0.4
Americas Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.0	0.0
Retail | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.0	5.4
Retail | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.0	$ 0.0
DN Now [Member] | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	184.8
DN Now [Member] | Severance | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	54.3
DN Now [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	11.9
DN Now [Member] | Other Restructuring [Member] | Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	7.1
DN Now [Member] | Eurasia Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	78.9
DN Now [Member] | Eurasia Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	2.5
DN Now [Member] | Americas Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	12.9
DN Now [Member] | Americas Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.1
DN Now [Member] | Retail | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	38.7
DN Now [Member] | Retail | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	$ 2.2