Employee Benefit Plans - Asset Category and Fair Value of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 42.8	$ 48.5	$ 41.1
Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	42.6	45.6
Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	0.2	2.9	$ 1.3
Equity funds
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 30.0	33.0
Equity funds | Minimum
Defined Benefit Plan Disclosure
Target Allocations by Asset Category (percent)	60.00%
Equity funds | Maximum
Defined Benefit Plan Disclosure
Target Allocations by Asset Category (percent)	68.00%
Equity funds | Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 30.0	33.0
Equity funds | Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Fixed income funds
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 12.6	12.6
Fixed income funds | Minimum
Defined Benefit Plan Disclosure
Target Allocations by Asset Category (percent)	26.00%
Fixed income funds | Maximum
Defined Benefit Plan Disclosure
Target Allocations by Asset Category (percent)	30.00%
Fixed income funds | Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 12.6	12.6
Fixed income funds | Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Other investments
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 0.2	2.9
Other investments | Minimum
Defined Benefit Plan Disclosure
Target Allocations by Asset Category (percent)	3.00%
Other investments | Maximum
Defined Benefit Plan Disclosure
Target Allocations by Asset Category (percent)	6.00%
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	$ 0.2	$ 2.9