Available-For-Sale Securities (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013
Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities Impairment Charge	$ 12,000,000
Nuclear Decommissioning Trust (NDT) Fund [Member] | Power [Member]
Schedule of Available-for-sale Securities [Line Items]
Decommissioning Liability, Noncurrent	369,000,000
Nuclear Decommissioning Trust (NDT) Fund [Member] | Power [Member] | Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Decommissioning Costs Including Contingencies	2,200,000,000
Nuclear Decommissioning Trust (NDT) Fund [Member] | Power [Member] | Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Decommissioning Costs Including Contingencies	2,400,000,000
Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member] | Power [Member]
Schedule of Available-for-sale Securities [Line Items]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent	141,000,000
Debt Securities [Member] | Rabbi Trusts [Member] | Power [Member]
Schedule of Available-for-sale Securities [Line Items]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent	$ 4,000,000