Commitments And Contingencies (Environmental Remediation Liability Disclosure) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Site Contingency [Line Items]
Balance at June 30, 2012	$ 150
Pacific Gas And Electric Company [Member]
Site Contingency [Line Items]
Balance at December 31, 2011	785
Transfer to regulatory account for recovery	100
Amounts not recoverable in customer rates	96
Less: Payments	(61)
Balance at June 30, 2012	$ 920