Pension and Postretirement Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension and Other Postretirement Benefits	$ 1.1	$ 1.3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.0	0.0
Other components of pension and postretirement benefit plans expense:
Interest cost on projected benefit obligation	6.0	4.2
Expected return on plan assets	(7.8)	(6.2)
Amortization of:
Prior service benefit	0.0	0.0
Actuarial loss	3.4	4.3
Total amortization	3.4	4.3
Pension / postretirement costs	1.6	2.3
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	11.0
Payment for Pension and Other Postretirement Benefits	1.9	1.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.2	0.1
Other components of pension and postretirement benefit plans expense:
Interest cost on projected benefit obligation	1.2	0.8
Expected return on plan assets	0.0	0.0
Amortization of:
Prior service benefit	(0.6)	(0.8)
Actuarial loss	0.4	1.0
Total amortization	(0.2)	0.2
Pension / postretirement costs	1.2	$ 1.1
Qualified Plan [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	$ 3.0
Nonqualified Plan [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year			$ 3.0