Retirement and Deferred Compensation Plans (Fair Value of Benefit Plan Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	$ 118	$ 115
Corporate Bonds [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets		1
U.S. Government Bonds [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	83	87
Cash And Invested Cash [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	26	19
Other Investments [Member]
Fair Value of Benefit Plans' Assets [Abstract]
Fair value of plan assets	$ 9	$ 8