Balance Sheet Components Regulatory Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	$ 100	$ 100
Pension and other postretirement plans	0	0
Deferred income taxes	0	0
Debt issuance costs	0	0
Deferred capital projects	14	19
Other	11	14
Total regulatory assets	125	133
Noncurrent Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	174	121
Pension and other postretirement plans	242	247
Deferred income taxes	87	86
Debt issuance costs	15	15
Deferred capital projects	0	0
Other	27	25
Total regulatory assets	545	494
Current Regulatory Liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Asset retirement removal costs	0	0
Trojan decommissioning activities	22	23
Asset retirement obligations	0	0
Other	37	37
Total regulatory liabilities	59	60
Noncurrent Regulatory Liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Asset retirement removal costs	813	804
Trojan decommissioning activities	29	34
Asset retirement obligations	40	39
Other	29	29
Total regulatory liabilities	$ 911	$ 906