Available-For-Sale Securities (Schedule Of Accounts Receivable And Accounts Payable) (Detail) (Nuclear Decommissioning Trust (NDT) Fund [Member], Power [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Nuclear Decommissioning Trust (NDT) Fund [Member] \| Power [Member]
Accounts Receivable	$ 45	$ 18
Accounts Payable	$ 57	$ 53

Available-For-Sale Securities (Schedule Of Accounts Receivable And Accounts Payable) (Detail) (Nuclear Decommissioning Trust (NDT) Fund [Member], Power [Member], USD $)
In Millions, unless otherwise specified

Jun. 30, 2013

Dec. 31, 2012

Nuclear Decommissioning Trust (NDT) Fund [Member] | Power [Member]

Accounts Receivable

$ 45

$ 18

Accounts Payable

$ 57

$ 53