Available-For-Sale Securities (Schedule Of Accounts Receivable And Accounts Payable) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Rabbi Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Accounts Receivable	$ 1	$ 1
Accounts Payable	0	2
Nuclear Decommissioning Trust (NDT) Fund [Member] | Power [Member]
Schedule of Available-for-sale Securities [Line Items]
Accounts Receivable	10	39
Accounts Payable	$ 2	$ 36