Resolution Of Remaining Chapter 11 Disputed Claims (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Resolution Of Remaining Chapter Eleven Disputed Claims [Line Items]
Escrow for payment of remaining net disputed claims	$ 494	$ 494
Balance at December 31, 2011	848
Interest accrued	13
Less: electricity supplier settlements	(23)
Balance at June 30, 2012	838
Interest accrued on disputed claims	320
Pacific Gas And Electric Company [Member]
Resolution Of Remaining Chapter Eleven Disputed Claims [Line Items]
Balance at June 30, 2012	164
Remaining disputed claims	674
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