Pension and Other Postretirement Benefits - Contributions to Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions to pension and other postretirement plans	$ 13.4	$ 37.5
Pensions
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions to pension and other postretirement plans	11.9	36.0
Other postretirement benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions to pension and other postretirement plans	1.5	1.5
Qualified Plan | Pensions | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions to pension and other postretirement plans	7.0	30.0
Nonqualified Plan | Pensions | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions to pension and other postretirement plans	$ 4.9	$ 6.0