Restructuring Costs Costs Recognized and Remaining Costs Expected To Be Incurred (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Restructuring Cost and Reserve [Line Items]
Termination benefits	$ 110.8
Restructuring Costs, Expected Costs	0.2
One-time Termination Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Termination benefits	45.6
Restructuring Costs, Expected Costs	0.0
Lease Termination Costs [Member]
Restructuring Cost and Reserve [Line Items]
Termination benefits	1.6
Restructuring Costs, Expected Costs	0.0
Accelerated Share Based Compensation [Member]
Restructuring Cost and Reserve [Line Items]
Termination benefits	23.8
Restructuring Costs, Expected Costs	0.0
Retention Expense [Member]
Restructuring Cost and Reserve [Line Items]
Termination benefits	38.5
Restructuring Costs, Expected Costs	0.2
Pension curtailment [Member]
Restructuring Cost and Reserve [Line Items]
Termination benefits	1.3
Restructuring Costs, Expected Costs	$ 0.0