Employee Retirement Benefits (Components Of Net Periodic Benefit Cost As Well As Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income For Qualified Plan And SERP) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Service cost	$ 9	$ 8	$ 11
Interest cost	12	13	13
Expected return on plan assets	(21)	(20)	(22)
Amortization of actuarial loss and prior service cost	3	1	1
Other	3	1	2
Net periodic benefit cost	6	3	5
Current year actuarial (gain) loss	38	(5)	7
Amortization of actuarial loss	(6)	(2)	(3)
Total recognized in other comprehensive (income) loss	32	(7)	4
Total recognized in net periodic benefit cost and other comprehensive (income) loss	$ 38	$ (4)	$ 9