Employee Retirement Plans - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (2,466.1)	$ (2,565.1)	$ (2,378.9)	$ (2,562.0)
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	15.0
Actual employer contributions to defined benefit plans	0.3	$ 0.2
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	1.1
Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	155.0
Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	185.0
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Defined Benefit Plan Disclosure [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(170.1)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Defined Benefit Plan Disclosure [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 132.5		$ (131.2)