Employee Benefits (Details) - Other Postretirement Benefit Plans, Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.2	$ 1.1	$ 3.6	$ 3.2
Interest cost	14.3	15.2	42.9	45.6
Expected return on plan assets	(15.0)	(13.4)	(45.0)	(40.2)
Amortization of net pension loss	4.0	3.2	12.0	9.6
Total periodic pension cost	4.5	$ 6.1	13.5	$ 18.2
Expected future benefit payments, remainder of the year	$ 60.0		60.0
Contributions by employer			$ 48.9