Pension Benefits - Narrative (Details) $ in Millions			12 Months Ended
	Aug. 22, 2019 USD ($)	Jul. 13, 2018 USD ($)	Dec. 31, 2020 USD ($) employees	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Employer Contributions	$ 55.3	$ 5.1
Defined contribution plan, cost			$ 26.1	$ 26.0	$ 15.1
Payment for Pension Benefits			0.0	55.3	5.1
Payment for Pension Benefits			0.0	55.3	5.1
Pension and Other Postretirement Benefits Expense (Reversal of Expense), Noncash			$ 50.6
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Number of participants and beneficiaries | employees			3,175
Contribution as a percentage of compensation			3.00%
Actuarial loss amortization period			27 years
Amounts that will be amortized from AOCI in next fiscal Year			$ 3.0
Employer Contributions			0.0	55.3
Unfunded liability			(23.1)	(4.1)
Pension expense			58.6	(5.4)	(4.3)
Unrecognized pension gain (loss) arising during the year			7.8	(4.2)	(11.5)
Payment for Pension Benefits			117.1
Payment for Pension Benefits			117.1
Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Unfunded liability			30.7	28.9
Pension expense			0.8	1.0	0.8
Unrecognized pension gain (loss) arising during the year			(2.7)	$ (5.6)	$ 1.3
Terminal Funding Annuity [Member]
Defined Benefit Plan Disclosure [Line Items]
Proceeds from Annuities and Investment Certificates			205.4
Proceeds from Annuities and Investment Certificates			$ 205.4