Balance Sheet Components Regulatory Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Jun. 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	664	637
Asset retirement obligations	38	36
Power Cost Adjustment Mechanism	14	10
Other	39	37
Total regulatory liabilities	755	720
Current Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	185	194
Pension and other postretirement plans	0	0
Deferred income taxes	0	0
Deferred broker settlements	7	11
Debt reacquisition costs	0	0
Other	5	11
Total regulatory assets	197	216
Noncurrent Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	119	172
Pension and other postretirement plans	285	295
Deferred income taxes	82	87
Deferred broker settlements	0	0
Debt reacquisition costs	25	28
Other	17	12
Total regulatory assets	$ 528	$ 594