Restructuring - Restructuring Charges By Plan (Details) $ in Millions	Dec. 31, 2020 USD ($)
Severance | DN Now Plan [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	$ 184.8
Severance | DN Now Plan [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	54.3
Severance | DN Now Plan [Member] | Eurasia Banking Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	78.9
Severance | DN Now Plan [Member] | Americas Banking Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	12.9
Severance | DN Now Plan [Member] | Retail Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	38.7
Severance | DN2020 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	95.8
Severance | DN2020 Plan [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	15.1
Severance | DN2020 Plan [Member] | Eurasia Banking Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	51.5
Severance | DN2020 Plan [Member] | Americas Banking Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	13.6
Severance | DN2020 Plan [Member] | Retail Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	15.6
Other Restructuring | DN Now Plan [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	5.9
Other Restructuring | DN Now Plan [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	1.6
Other Restructuring | DN Now Plan [Member] | Eurasia Banking Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	2.0
Other Restructuring | DN Now Plan [Member] | Americas Banking Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	0.1
Other Restructuring | DN Now Plan [Member] | Retail Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	$ 2.2