Restructuring (Textuals) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2019
Unusual or Infrequent Item [Line Items]
Restructuring Charges	$ 3.8	$ 3.9
DN Now Plan [Member] | Minimum [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Expected Cost	170.0
DN Now Plan [Member] | Maximum [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Expected Cost	200.0
DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring Charges	3.8
Anticipated Annual Synergies	130.0
DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring Charges	3.8
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	3.8	3.9
Subsequent Event [Member] | DN Now Plan [Member]
Unusual or Infrequent Item [Line Items]
Anticipated Annual Synergies			$ 160.0
Severance
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	166.7
Restructuring Charges	3.8	3.9
Severance | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	62.7
Severance | DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	95.8
Severance | Strategic Alliance Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	8.2
Severance | Eurasia Banking
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	94.5
Restructuring Charges	1.5	2.5
Severance | Eurasia Banking | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	34.8
Severance | Eurasia Banking | DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	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
Severance | Americas Banking
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	22.6
Restructuring Charges	0.4	0.1
Severance | Americas Banking | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	9.0
Severance | Americas Banking | DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	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
Severance | Retail
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	28.9
Restructuring Charges	0.8	0.5
Severance | Retail | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	13.3
Severance | Retail | DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	15.6
Severance | Retail | Strategic Alliance Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	0.0
Severance | Corporate
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	20.7
Restructuring Charges	1.1	$ 0.8
Severance | Corporate | DN Now [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	5.6
Severance | Corporate | DN2020 Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	15.1
Severance | Corporate | Strategic Alliance Plan [Member]
Unusual or Infrequent Item [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	$ 0.0