Employee Retirement Plans - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (2,459.3)	$ (4,643.4)	$ (2,459.3)	$ (4,643.4)	$ (2,529.6)	$ (2,565.1)	$ (2,562.0)	$ (4,671.8)	$ (4,834.6)	$ (4,858.0)
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	25.0		25.0
Actual employer contributions to defined benefit plans	0.0	$ 28.0	0.2	$ 31.7
Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	145.0		145.0
Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	$ 195.0		$ 195.0
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Defined Benefit Plan Disclosure [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest							(140.4)
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							$ (107.2)