Employee Benefits - Accumulated Benefit Obligations (Details) - Pension Plan - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 2,992.9	$ 2,804.9
Information for pension plans with an accumulated benefit obligation in excess of plan assets
Projected benefit obligation	1,810.1	1,930.8
Accumulated benefit obligation	1,754.2	1,882.2
Fair value of plan assets	$ 1,504.6	$ 1,572.7