Employee Benefits (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Employee Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Number of Non-Qualified Retirement Plans	2
Short Term Incentive Plan Payout	$ 9.7	$ 12.5	$ 10.5
Retirement Income Plan | Years Of Service
Employee Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Years of Service Requisite	1