Restructuring - Restructuring Charges By Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 8.6	$ 38.3	$ 19.8	$ 44.4
Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges	8.6	38.3	19.7	44.4
Eurasia Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1.3	12.3	4.1	16.0
Americas Banking | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.6	7.5	1.2	7.8
Americas Banking | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0	0.0	0.1	0.0
Retail | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.9	6.0	4.5	6.8
Corporate | Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges	5.8	$ 12.5	9.9	13.8
DN2020 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges				6.0
Strategic Alliance Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 0.1
DN Now [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 8.6		$ 19.8