Retirement and Deferred Compensation Plans (Fair Value of Benefit Plan Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	$ 1,736	$ 1,589
Corporate Bonds [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	320	274
U.S. Government Bonds [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	246	280
Foreign Government Bonds [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	138	67
State And Municipal Bonds [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	29	29
Limited Partnerships And Common And Preferred Stock [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	671	599
Bulk Annuity Insurance Policy [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	178	165
Invested Cash [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	88	106
Other Investments [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	$ 66	$ 69