Pension Plans - Fair Value of Pension Plan Assets (Details) - Pension Plan - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 13.0	$ 16.8
Total assets at fair value		179.8	198.0
Quoted Prices in Active Market (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2.7	5.0
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		10.3	11.8
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0	0.0
Cash and equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2.7	5.0
Cash and equivalents | Quoted Prices in Active Market (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2.7	5.0
Cash and equivalents | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0	0.0
Cash and equivalents | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0	0.0
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.4	0.3
Corporate bonds | Quoted Prices in Active Market (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0	0.0
Corporate bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.4	0.3
Corporate bonds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0	0.0
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		8.1	9.7
Alternative Investment	[1]	165.6	180.2
Mutual funds | Quoted Prices in Active Market (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0	0.0
Mutual funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		8.1	9.7
Mutual funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0	0.0
Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1.8	1.8
Insurance contracts | Quoted Prices in Active Market (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0	0.0
Insurance contracts | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1.8	1.8
Insurance contracts | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0	0.0
Other private investments
Defined Benefit Plan Disclosure [Line Items]
Alternative Investment	[1]	$ 1.2	$ 1.0

[1] The fair value amounts presented in the table above are intended to permit reconciliation of the fair value hierarchy to the total fair value of plan assets.