Employee Benefit Plans, Weighted-Average Assumptions (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Minimum [Member]
Employee Benefit Plans (Textual)
Yield curve maturities	6 months
Maximum [Member]
Employee Benefit Plans (Textual)
Yield curve maturities	99 years
Pension Plans [Member]
Weighted Average Assumptions Used to Determine Benefit Obligation
Discount rate	3.58%	4.08%
Rate of compensation increase	3.86%	3.81%
Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost
Discount rate	4.08%	4.45%	4.10%
Expected long-term rate of return on plan assets	7.29%	7.28%	7.29%
Rate of compensation increase	3.81%	3.79%	3.78%
Other Postretirement Benefit Plans [Member]
Weighted Average Assumptions Used to Determine Benefit Obligation
Discount rate	3.72%	4.26%
Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost
Discount rate	4.26%	4.53%	4.13%