Employee Benefits (Details) - Other Postretirement Benefit Plans, Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.2	$ 1.1	$ 2.4	$ 2.1
Interest cost	14.3	15.2	28.6	30.4
Expected return on plan assets	(15.0)	(13.4)	(30.0)	(26.8)
Amortization of net pension loss	4.0	3.2	8.0	6.4
Total periodic pension cost	4.5	$ 6.1	9.0	$ 12.1
Expected future benefit payments, remainder of the year	$ 60.3		60.3
Contributions by employer			$ 24.4