Commitments And Contingencies (Environmental Remediation Liability Composed) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Utility-owned natural gas compressor site near Hinkley, California	$ 268	[1]	$ 239	[1]
Utility-owned natural gas compressor site near Topock, Arizona	197	[1]	226	[1]
Utility-owned generation facilities (other than for fossil fuel-fired), other facilities, and third-party disposal sites	179		181
Former MGP sites owned by the Utility or third parties	165		158
Fossil fuel-fired generation facilities formerly owned by the Utility	85		87
Decommissioning fossil fuel-fired generation facilities and sites	20		19
Total environmental remediation liability	$ 914		$ 910

[1] See "Hinkley Natural Gas Compressor Site" below.