Employee Benefits (Details) - Other Postretirement Benefit Plans, Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.6	$ 1.2
Interest cost	14.0	14.3
Expected return on plan assets	(14.1)	(15.0)
Amortization of net pension loss	3.4	4.0
Total periodic pension cost	4.9	$ 4.5
Expected future benefit payments, remainder of the year	45.3
Contributions by employer	$ 0.2