Employee Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer			$ 3.8
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	$ 0.9		0.9
Defined Contribution Plan, Cost	2.8	$ 2.7	8.4	$ 8.0
Retirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.7	0.7	2.3	2.5
Interest cost	0.9	1.2	3.1	3.4
Expected return on plan assets	(1.6)	(1.7)	(4.8)	(5.7)
Amortization of unrecognized net loss	0.4	0.3	1.6	1.1
Settlement charge	0.6	0.4	2.7	2.6
Net periodic benefit cost	1.0	0.9	4.9	3.9
PBOP
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.0	0.0	0.0	0.1
Interest cost	0.4	0.4	1.1	1.1
Expected return on plan assets	(0.6)	(1.2)	(2.2)	(3.5)
Amortization of unrecognized net loss	0.0	0.0	0.0	0.0
Settlement charge	0.0	0.0	0.0	0.0
Net periodic benefit cost	$ (0.2)	$ (0.8)	$ (1.1)	$ (2.3)