Restructuring - Restructuring Charges By Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 10.0	$ 3.8
Restructuring and Related Cost, Cost Incurred to Date	119.1
Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	10.0	3.8
Eurasia Banking
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	49.1
Eurasia Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	2.3	1.5
Americas Banking
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	10.9
Americas Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.4	0.4
Retail
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	27.6
Retail | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	5.4	0.8
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	31.5
Corporate | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	1.9	$ 1.1
DN Now [Member] | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	119.0
DN Now [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.1
DN Now [Member] | Eurasia Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	49.1
DN Now [Member] | Eurasia Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.0
DN Now [Member] | Americas Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	10.8
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	27.6
DN Now [Member] | Retail | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.0
DN Now [Member] | Corporate | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	31.5
DN Now [Member] | Corporate | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	$ 0.0