Employee Benefits (Net Periodic Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net periodic benefit cost:
Service cost	$ 0.0	$ 5.4
Interest cost	44.1	51.1
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (income):
Income tax provision (benefit) related to amounts in other comprehensive income	(0.1)	13.3
Other Postretirement Benefits Plan
Net periodic benefit cost:
Service cost	0.0	5.4	$ 6.5
Interest cost	44.1	51.1	55.9
Expected return on plan assets	(60.0)	(59.3)	(56.2)
Amortization of prior net losses	14.6	15.5	13.7
Amortization of prior net service credit	(0.4)	0.0	0.0
Settlement adjustment	10.9	7.6	0.0
Net periodic pension cost	9.2	20.3	19.9
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (income):
Net actuarial gains (losses) and other adjustments	(0.9)	(43.7)	69.5
Net prior service credit	0.0	(10.7)	0.0
Settlement adjustment	(10.9)	(7.6)	0.0
Amortization of prior net losses	(14.6)	(15.5)	(13.7)
Amortization of prior net service credit	0.4	0.0	0.0
Total recognized in other comprehensive loss (income)	(26.0)	(77.5)	55.8
Total recognized in net periodic benefit cost and other comprehensive loss (income)	$ (16.8)	$ (57.2)	$ 75.7