Pension and Other Postretirement Benefits - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Requisite service period			3 years
Contributions by employer	$ 10.0	$ 60.0	$ 11.7	$ 81.6
Defined Benefit Plan, Expected Future Benefit Payment, Remainder of Fiscal Year	$ 0.0		$ 0.0