Pension and Other Postretirement Benefit Plans - Information for Pension Plans with an Accumulated Benefit Obligation in Excess of Plan Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Plan Amendments		$ 0.0	$ (1.5)
Projected Benefit Obligation		854.0	747.0
Accumulated Benefit Obligation		812.0	713.7
Fair Value of Plan Assets		699.6	598.0
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Plan Amendments	[1]	$ (34.6)	$ (2.1)

[1] Plan design changes under the other postretirement benefit plans resulted in a decrease to the benefit obligation of $34.6 million in 2019.