Pension and Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Plan and SERP
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 3.7	$ 3.6
Expected return on plan assets	(6.4)	(7.7)
Amortization of net actuarial loss	1.2	0.8
Net periodic (benefit) cost	(1.5)	(3.3)
Employer contributions, net	0.2	0.2
Postretirement Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	0.0	0.1
Expected return on plan assets	0.0	(0.1)
Amortization of net actuarial loss	0.1	0.1
Net periodic (benefit) cost	0.1	0.1
Employer contributions, net	$ (0.3)	$ (0.1)