Restructuring (Textuals) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended	36 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2021
Unusual or Infrequent Item [Line Items]
Restructuring charges	$ 8.6	$ 38.3	$ 19.8	$ 44.4
DN Now Plan [Member] | Minimum [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Expected Cost	125.0		125.0
DN Now Plan [Member] | Maximum [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Expected Cost	175.0		175.0
DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring charges	8.6		19.8
DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring charges				6.0
Strategic Alliance Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring charges				0.1
Segment Reconciling Items [Member]
Unusual or Infrequent Item [Line Items]
Restructuring charges	19.7	40.8	63.1	46.9
Subsequent Event [Member] | DN Now Plan [Member]
Unusual or Infrequent Item [Line Items]
Anticipated Annual Synergies					$ 175.0	$ 400.0
Severance
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	182.7		182.7
Restructuring charges	8.6	38.3	19.7	44.4
Severance | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	78.6		78.6
Severance | DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	95.8		95.8
Severance | Strategic Alliance Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	8.2		8.2
Severance | Eurasia Banking
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	97.1		97.1
Restructuring charges	1.3	12.3	4.1	16.0
Severance | Eurasia Banking | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	37.4		37.4
Severance | Eurasia Banking | DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	51.5		51.5
Severance | Eurasia Banking | Strategic Alliance Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	8.2		8.2
Severance | Americas Banking
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	23.5		23.5
Restructuring charges	0.6	7.5	1.2	7.8
Severance | Americas Banking | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	9.8		9.8
Severance | Americas Banking | DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	13.6		13.6
Severance | Americas Banking | Strategic Alliance Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.0		0.0
Severance | Retail
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	32.6		32.6
Restructuring charges	0.9	6.0	4.5	6.8
Severance | Retail | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	17.0		17.0
Severance | Retail | DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	15.6		15.6
Severance | Retail | Strategic Alliance Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.0		0.0
Severance | Corporate
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	29.5		29.5
Restructuring charges	5.8	12.5	9.9	13.8
Severance | Corporate | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	14.4		14.4
Severance | Corporate | DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	15.1		15.1
Severance | Corporate | Strategic Alliance Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.0		0.0
Other Restructuring [Member] | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.1		0.1
Other Restructuring [Member] | Eurasia Banking | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.0		0.0
Other Restructuring [Member] | Americas Banking
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.1		0.1
Restructuring charges	0.0	$ 0.0	0.1	$ 0.0
Other Restructuring [Member] | Retail | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.0		0.0
Other Restructuring [Member] | Corporate | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	$ 0.0		$ 0.0