Regulatory Assets, Liabilities, And Balancing Accounts (Current Regulatory Balancing Accounts, Net) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	$ 784	$ 708
Utility Generation [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	412	241
Distribution Revenue Adjustment Mechanism [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	422	223
Public Purpose Programs [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	96	97
Hazardous Substance [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	56	57
Gas Fixed Cost [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	(101)	16
Energy Procurement [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	(129)	(48)
Other Current Balancing Accounts [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	136	227
Energy Recovery Bonds [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	$ (108)	$ (105)