EBP Key Assumptions (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits [Member]
Weighted average assumptions utilized to determine benefit obligations
Rate of compensation increase	4.88%	4.62%
Discount rate	4.38%	3.96%
Weighted average assumptions utilized to determine net periodic benefit cost
Discount rate	3.96%	4.68%	3.43%
Expected long-term rate of return on plan assets	6.38%	6.85%	5.90%
Rate of compensation increase	4.62%	4.56%	4.57%
Other Postretirement Benefits [Member]
Weighted average assumptions utilized to determine benefit obligations
Discount rate	4.50%	4.12%
Weighted average assumptions utilized to determine net periodic benefit cost
Discount rate	4.12%	4.80%	3.97%
Expected long-term rate of return on plan assets	5.70%	6.11%	5.26%
One percentage point change in assumed health care cost trend rates effects
Effect on total of service and interest cost components, Point increase	$ 0
Effect on total of service and interest cost components, Point decrease	0
Effect on other postretirement benefit obligation, Point increase	7
Effect on other postretirement benefit obligation, Point decrease	$ (6)
Health care cost trend rate assumed for next fiscal year	7.90%
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	2025