Restructuring Restructuring - Narrative (Details) - USD ($) $ in Millions		12 Months Ended	17 Months Ended
	Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Length of information technology services agreement (in years)	5 years
Contract Cost, Total	$ 400.0
Minimum
Restructuring Cost and Reserve [Line Items]
Contract Cost, Expected Annual Cost	70.0
Maximum
Restructuring Cost and Reserve [Line Items]
Contract Cost, Expected Annual Cost	$ 90.0
2016 Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		$ 82.0		$ 116.0
Transition costs		17.0		17.0
Asset write-off costs		16.0		$ 16.0
Payments		39.0
2016 Restructuring [Member] | Expected restructuring expenses through completion
Restructuring Cost and Reserve [Line Items]
Transition costs			$ 35.0
Asset write-off costs			$ 16.0
Organizational restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		4.0
Payments		$ 0.0