Pension and Other Postemployment Benefits (Details 2)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average discount rate	4.25%	4.50%	4.25%
Expected long-term return on plan assets	7.50%	7.50%	7.75%
Rate of compensation increase	4.20%	4.20%	4.20%
OPEB
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average discount rate	4.00%	4.25%	4.00%
Expected long-term return on plan assets	7.50%	7.50%	7.75%