Pension and Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Pension Plan and SERP
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 3.3	$ 3.7
Expected return on plan assets	(7.6)	(6.4)
Amortization of net actuarial loss	1.0	1.2
Net periodic (benefit) cost	(3.3)	(1.5)
Employer contributions, net	0.2	0.2
Postretirement Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	0.0	0.0
Expected return on plan assets	0.0	0.0
Amortization of net actuarial loss	0.0	0.1
Net periodic (benefit) cost	0.0	0.1
Employer contributions, net	$ (0.4)	$ (0.3)
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	45.00%		40.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	55.00%		60.00%