Commitments And Contingencies (Environmental Remediation Liability Composed) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Utility-owned natural gas compressor site near Hinkley, California	$ 270	[1]	$ 239	[1]
Utility-owned natural gas compressor site near Topock, Arizona	207	[1]	226	[1]
Utility-owned generation facilities (other than for fossil fuel-fired), other facilities, and third-party disposal sites	181		181
Former MGP sites owned by the Utility or third parties	169		158
Fossil fuel-fired generation facilities formerly owned by the Utility	88		87
Decommissioning fossil fuel-fired generation facilities and sites	19		19
Total environmental remediation liability	$ 934		$ 910

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