Pension Plans - Qualified and Non-Qualified Plans - Adjustments to Equity (Details) - Pension Plan [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Change in equity as a result of change in deferred net loss	$ (2.3)	$ 2.1	$ (1.3)
Change in equity as result of change in deferred net loss taxes	$ 0.0	$ 0.5	$ (0.4)