Employee Benefit Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of net periodic benefit cost:
Service cost	$ 1.7	$ 1.5	$ 2.9
Interest cost	9.3	10.1	9.9
Expected return on plan assets	(12.5)	(13.0)	(14.7)
Recognized net actuarial (gain)	(0.4)	0.0	0.0
Amortization of prior service cost	0.1	0.1	0.1
Net periodic benefit (income)	$ (1.8)	$ (1.3)	$ (1.8)
Weighted average assumptions used to determine net periodic benefit cost:
Discount rate	4.07%	4.19%	3.70%
Expected return on plan assets	5.36%	5.56%	5.64%