Balance Sheet Components Regulatory Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 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	4	6
Total regulatory liabilities	4	6
Noncurrent Regulatory Liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Asset retirement removal costs	678	637
Asset retirement obligations	39	36
Power Cost Adjustment Mechanism	6	10
Other	37	37
Total regulatory liabilities	760	720
Current Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	142	194
Pension and other postretirement plans	0	0
Deferred income taxes	0	0
Deferred broker settlements	9	11
Debt reacquisition costs	0	0
Other	3	11
Total regulatory assets	154	216
Noncurrent Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	85	172
Pension and other postretirement plans	280	295
Deferred income taxes	78	87
Deferred broker settlements	1	0
Debt reacquisition costs	23	28
Other	23	12
Total regulatory assets	$ 490	$ 594