Employee Benefit Plans (Components Of Net Periodic Pension Costs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Regulatory asset amortization	$ 14	$ 16	$ 10
Qualified Pension Plans [Member]
Service cost	96	96	85
Interest cost on benefit obligation	232	248	257
Expected return on plan assets	(384)	(378)	(362)
Amortization of prior service cost (credit)	6	5	7
Amortization of loss (gain)	77	50	2
Settlement and contractual termination benefit cost		13
Other	18	18	17
Net periodic costs	45	52	6
Non-Qualified Pension Plans [Member]
Service cost	1	1	2
Interest cost on benefit obligation	8	9	10
Amortization of prior service cost (credit)	2	2	2
Settlement credit			(1)
Net periodic costs	11	12	13
Other Post-Retirement Benefit Plans [Member]
Service cost	7	7	7
Interest cost on benefit obligation	35	38	46
Expected return on plan assets	(15)	(15)	(16)
Amortization of prior service cost (credit)	(8)	(8)	(8)
Amortization of net transition liability	10	11	10
Amortization of loss (gain)	(3)	(5)	(5)
Net periodic costs	26	28	34
Regulatory asset amortization	$ 8	$ 9	$ 9