Employee Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 59	$ 52	$ 55
Interest cost		77	76	71
Expected return on plan assets		(97)	(107)	(112)
Amortization of prior service cost		15	15	19
Amortization of net actuarial loss		4	4	4
Net periodic benefit cost		58	40	37
Pension Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		472	453	479
Interest cost		714	715	673
Expected return on plan assets		(770)	(828)	(873)
Amortization of prior service cost		(7)	8	15
Amortization of net actuarial loss		22	24	10
Net periodic benefit cost		431	372	304
Less: transfer to regulatory account	[1]	(92)	(34)	34
Total		$ 339	$ 338	$ 338

[1] The Utility recorded these amounts to a regulatory account as they are probable of recovery from customers in future rates.