Employee Benefits (Details) - Other Postretirement Benefit Plans, Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.6	$ 1.2	$ 3.2	$ 2.4
Interest cost	14.0	14.3	28.0	28.6
Expected return on plan assets	(14.1)	(15.0)	(28.2)	(30.0)
Amortization of net pension loss	3.4	4.0	6.8	8.0
Total periodic pension cost	4.9	$ 4.5	9.8	$ 9.0
Expected future benefit payments, remainder of the year	$ 45.4		45.4
Contributions by employer			$ 13.5