Commitments And Contingencies (Nuclear Insurance) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Long-term Purchase Commitment [Line Items]
Coverage for purchased public liability insurance, per incident	$ 375
Diablo Canyon [Member]
Long-term Purchase Commitment [Line Items]
Maximum public liability per nuclear incident under Price-Anderson Act	13,600
Maximum available public liability insurance for Diablo Canyon as required by Price-Anderson Act	375
Diablo Canyon [Member] | Nuclear Incident [Member]
Long-term Purchase Commitment [Line Items]
Amount of property damage and business interruption coverage provided by NEIL for Diablo Canyon	3,200
Diablo Canyon [Member] | Non Nuclear Incident [Member]
Long-term Purchase Commitment [Line Items]
Amount of property damage and business interruption coverage provided by NEIL for Diablo Canyon	2,000
Humboldt Bay Unit [Member]
Long-term Purchase Commitment [Line Items]
Amount of property damage coverage provided by NEIL	131
Amount of indemnification from the NRC for public liability arising from nuclear incidents	500
Amount of liability insurance for Humboldt Bay Unit 3	$ 53