Employee Benefit Plans (Assumptions in Determining Net Periodic Benefit Costs) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Assumptions used in determining net periodic benefit costs [Abstract]
Weighted average discount rate	4.30%	4.13%	4.10%
Weighted average expected rate of return on plan assets	6.00%	6.00%	6.25%
Pension Benefits | Minimum
Assumptions used in determining net periodic benefit costs [Abstract]
Rate of compensation increase	2.25%	2.25%	2.25%
Pension Benefits | Maximum
Assumptions used in determining net periodic benefit costs [Abstract]
Rate of compensation increase	8.50%	8.50%	8.50%
Other Postretirement Benefits
Assumptions used in determining net periodic benefit costs [Abstract]
Weighted average discount rate	4.45%	4.37%	4.10%
Weighted average expected rate of return on plan assets	5.36%	5.53%	5.70%