Resolution Of Remaining Chapter 11 Disputed Claims (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Resolution Of Remaining Chapter Eleven Disputed Claims [Line Items]
Escrow for payment of remaining net disputed claims		$ 494
Balance at December 31, 2011	848
Interest accrued	20
Less: electricity supplier settlements	(24)
Balance at September 30, 2012	844
Pacific Gas And Electric Company [Member]
Resolution Of Remaining Chapter Eleven Disputed Claims [Line Items]
Interest accrued	680
Remaining disputed claims	164
CAISO And PX [Member]
Resolution Of Remaining Chapter Eleven Disputed Claims [Line Items]
Carrying amounts due from CAISO and PX as of the balance sheet date for disputed claims related to the Chapter 11 Filing	$ 301	$ 320