EBP Key Assumptions (Details 3)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits [Member]
Weighted average assumptions utilized to determine benefit obligations
Discount rate	4.34%	3.66%
Rate of compensation increase	4.83%	4.93%
Cash balance interest crediting rate	4.25%	4.25%
Weighted average assumptions utilized to determine net periodic benefit cost (credit)
Discount rate	3.67%	4.17%	4.37%
Expected long-term rate of return on plan assets	5.34%	6.45%	6.85%
Rate of compensation increase	4.93%	4.87%	4.88%
Cash balance interest crediting rate	4.25%	4.25%	4.25%
Other Postretirement Benefits [Member]
Weighted average assumptions utilized to determine benefit obligations
Discount rate	4.39%	3.71%
Weighted average assumptions utilized to determine net periodic benefit cost (credit)
Discount rate	3.71%	4.27%	4.50%
Expected long-term rate of return on plan assets	4.95%	5.53%	6.11%
Health care cost trend rate assumed for next fiscal year	7.50%
Direction and pattern of change for assumed health care cost trend rate	decreases
Ultimate health care cost trend rate	4.50%
Year that rate reaches ultimate trend rate	2026