Pension Plans - Fair Value of Pension Plan Assets (Details) - Pension Plan - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 56.2	$ 13.0
Total assets at fair value		224.1	179.8
Quoted Prices in Active Market (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		12.4	2.7
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		43.8	10.3
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		3.4	2.7
Cash and equivalents | Quoted Prices in Active Market (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3.4	2.7
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
Common stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		7.3
Common stock | Quoted Prices in Active Market (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		7.3
Common stock | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Common stock | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Preferred stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1.7
Preferred stock | Quoted Prices in Active Market (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1.7
Preferred stock | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Preferred stock | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		8.5	0.4
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		8.5	0.4
Corporate bonds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0	0.0
Government issued
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2.7
Government issued | Quoted Prices in Active Market (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Government issued | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2.7
Government issued | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		30.7	8.1
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		30.7	8.1
Mutual funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0	0.0
Mutual funds | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Investments measured at NAV	[1]	155.9	165.6
Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1.9	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		1.9	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 | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Investments measured at NAV	[1]	$ 12.0	$ 1.2

[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