Balance Sheet Components Regulatory Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	$ 88	$ 123
Pension and other postretirement plans	0	0
Deferred income taxes	0	0
Deferred broker settlements	8	20
Debt reacquisition costs	0	0
Deferred capital projects	0	0
Other	3	1
Total regulatory assets	99	144
Noncurrent Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	71	71
Pension and other postretirement plans	301	321
Deferred income taxes	74	80
Deferred broker settlements	0	1
Debt reacquisition costs	18	22
Deferred capital projects	29	16
Other	11	13
Total regulatory assets	504	524
Current Regulatory Liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Asset retirement removal costs	0	0
regulatory liabilities - trojan decommissioning trust	0	0
Asset retirement obligations	0	0
Other	4	12
Total regulatory liabilities	4	12
Noncurrent Regulatory Liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Asset retirement removal costs	733	692
regulatory liabilities - trojan decommissioning trust	41	0
Asset retirement obligations	39	39
Other	39	34
Total regulatory liabilities	$ 852	$ 765