Employee Benefit Plans - Fair Value Measurements (Details) - Quoted Prices in Active Markets for Identical Assets (Level 1) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans
Fair value of plan assets	$ 156.5	$ 148.6
Cash
Defined Benefit Plans
Fair value of plan assets	0.6	0.6
U.S. treasury bonds
Defined Benefit Plans
Fair value of plan assets	20.9	27.0
Equity mutual funds
Defined Benefit Plans
Fair value of plan assets	$ 17.8	17.8
Target allocation percentage of investments	12.00%
Fixed income mutual funds
Defined Benefit Plans
Fair value of plan assets	$ 117.2	$ 103.2
Target allocation percentage of investments	88.00%