Balance Sheet Components Regulatory Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current Regulatory Liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Asset retirement removal costs	$ 0	$ 0
Asset retirement obligations	0	0
Power Cost Adjustment Mechanism	0	0
Other	3	6
Total regulatory liabilities	3	6
Noncurrent Regulatory Liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Asset retirement removal costs	651	637
Asset retirement obligations	37	36
Power Cost Adjustment Mechanism	14	10
Other	40	37
Total regulatory liabilities	742	720
Current Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	216	194
Pension and other postretirement plans	0	0
Deferred income taxes	0	0
Deferred broker settlements	9	11
Debt reacquisition costs	0	0
Other	7	11
Total regulatory assets	232	216
Noncurrent Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	172	172
Pension and other postretirement plans	290	295
Deferred income taxes	85	87
Deferred broker settlements	0	0
Debt reacquisition costs	27	28
Other	14	12
Total regulatory assets	$ 588	$ 594