Restructuring - Restructuring Charges By Plan (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Severance
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	$ 101.1
Severance | Services Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	56.0
Severance | Software Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	10.3
Severance | Systems Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	25.6
Severance | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	9.2
Severance | Global Realigment Plan
Restructuring Cost and Reserve [Line Items]
Costs incurred to date		$ 105.0
Severance | DN2020 Plan [Member] | Services Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	52.9
Severance | DN2020 Plan [Member] | Software Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	8.0
Severance | DN2020 Plan [Member] | Systems Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	21.0
Severance | DN2020 Plan [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	7.9
Severance | Delta Program [Member] [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	3.2
Severance | Strategic Alliance Plan [Member]
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	$ 8.1
Other Restructuring [Member] | Global Realigment Plan
Restructuring Cost and Reserve [Line Items]
Costs incurred to date		$ 3.5