Employee Benefits (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Employer Contribution	$ 9.4
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	10.0
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Employer Contribution	0.3
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	$ 0.5