Employee Benefit Plans - Asset Category and Fair Value of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 53.9	$ 49.1	$ 42.8
Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	52.1	48.8
Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 1.8	0.3	$ 0.2
Equity funds
Defined Benefit Plan Disclosure
Target Allocations by Asset Category	68.00%
Fair value of plan assets	$ 38.9	36.0
Equity funds | Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	38.9	36.0
Equity funds | Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 0.0	0.0
Fixed income funds
Defined Benefit Plan Disclosure
Target Allocations by Asset Category	26.00%
Fair value of plan assets	$ 13.2	12.8
Fixed income funds | Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	13.2	12.8
Fixed income funds | Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 0.0	0.0
Other investments
Defined Benefit Plan Disclosure
Target Allocations by Asset Category	6.00%
Fair value of plan assets	$ 1.8	0.3
Other investments | Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Other investments | Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 1.8	$ 0.3