Balance Sheet Components Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Current Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	$ 124	$ 120
Pension and other postretirement plans	0	0
Deferred income taxes	0	0
Debt issuance costs	0	0
Other	7	9
Total regulatory assets	131	129
Noncurrent Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	159	161
Pension and other postretirement plans	235	239
Deferred income taxes	86	86
Debt issuance costs	24	16
Other	22	22
Total regulatory assets	526	524
Current Regulatory Liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Asset retirement removal costs	0	0
Trojan decommissioning activities	21	17
Asset retirement obligations	0	0
Other	36	38
Total regulatory liabilities	57	55
Noncurrent Regulatory Liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Asset retirement removal costs	850	837
Trojan decommissioning activities	11	15
Asset retirement obligations	46	45
Other	31	31
Total regulatory liabilities	$ 938	$ 928