Benefit Plans Benefit Plans - Accumulated Benefit Obligation In Excess of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Document Period End Date	Dec. 31, 2016
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 1,101.4	$ 546.4
Accumulated benefit obligation	1,092.7	546.1
Fair value of plan assets	$ 834.6	$ 347.9