Resolution Of Remaining Chapter 11 Disputed Claims (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Pacific Gas And Electric Company [Member]
Resolution Of Remaining Chapter Eleven Disputed Claims [Line Items]
Interest accrued	$ 698	$ 685
Remaining disputed claims	156	157
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	$ 291	$ 291