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Employee Benefit Plans (Schedule Of Assumed Health Care Cost Trend) (Details)
$ in Millions
12 Months Ended
Dec. 31, 2017
USD ($)
Employee Benefit Plans [Abstract]  
Effect on postretirement benefit obligation, One-Percentage-Point Increase $ 128
Effect on postretirement benefit obligation, One-Percentage-Point Decrease (129)
Effect on service and interest cost, One-Percentage-Point Increase 9
Effect on service and interest cost, One-Percentage-Point Decrease $ (10)
Assumed health care cost trend rate 6.80%
Ultimate trend rate 4.50%
Assumed return 6.20%
10 year actual rate of return 7.80%
Number of Aa-grade non-callable bonds used to develop the yield curve for rate used 623