Benefit Plans - Pension and Other Post-retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Vesting period	3 years
Plan assets	$ 31.0	$ 180.7
Company contributions	11.1
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit	(11.8)
Pension plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Lump-sum payments	(1.5)	0.0
Benefit obligation	112.1	277.9	$ 473.8
Plan assets	31.0	180.7	$ 382.8
Company contributions	18.0	$ 7.1
Pension plans | Salaried Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Lump-sum payments	$ 171.9
Restricted Stock And Restricted Stock Units (RSUs) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Vesting period	3 years