Restructuring - Restructuring Charges By Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 50.2	$ 65.0	$ 49.4
Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	213.1
Restructuring Charges	50.1	65.0	49.4
Severance | Eurasia Banking Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	106.5
Restructuring Charges	13.5	37.1	24.6
Severance | Americas Banking Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	24.1
Restructuring Charges	1.8	8.9	4.2
Severance | Retail Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	37.8
Restructuring Charges	9.7	13.3	14.8
Severance | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	44.7
Restructuring Charges	25.1	5.7	5.8
Other - Americas Banking | Americas Banking Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.1	0.0
DN2020 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		$ 6.0	$ 47.0
DN2020 Plan [Member] | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	95.8
DN2020 Plan [Member] | Severance | Eurasia Banking Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	51.5
DN2020 Plan [Member] | Severance | Americas Banking Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	13.6
DN2020 Plan [Member] | Severance | Retail Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	15.6
DN2020 Plan [Member] | Severance | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	$ 15.1