Pension and Other Post Retirement Benefits - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) Entity Postretirement_Plan	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of Postretirement Plans | Postretirement_Plan	2
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 2.2	$ 1.9	$ 1.8
Defined Benefit Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	(2.1)	(0.2)	(6.1)
Defined Benefit Plan, Service Cost	8.2	6.5	$ 6.1
Aggregate accumulated benefit obligation	394.8	457.0
Defined benefit plan, estimated future employer contributions in next fiscal year	5.7
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 6.6	$ 1.6
Loan Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of Limited Liability Company with Investments | Entity	1