Employee Benefits (Details) - Other Postretirement Benefit Plans, Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.6	$ 1.2	$ 4.8	$ 3.6
Interest cost	14.0	14.3	42.0	42.9
Expected return on plan assets	(14.2)	(15.0)	(42.4)	(45.0)
Amortization of net pension loss	3.5	4.0	10.3	12.0
Total periodic pension cost	4.9	$ 4.5	14.7	$ 13.5
Expected future benefit payments, remainder of the year	$ 45.4		45.4
Contributions by employer			$ 33.1