Balance Sheet Components Electric Utility Plant, Net (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Amortization of Intangible Assets	$ 12	$ 10	$ 23	$ 22
Electric utility plant	9,674		9,674		$ 9,534
Construction work-in-progress	346		346		213
Total cost	10,020		10,020		9,747
Less: accumulated depreciation and amortization	(3,447)		(3,447)		(3,313)
Electric utility plant, net	$ 6,573		$ 6,573		$ 6,434

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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-Section 50
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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
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-Name Accounting Standards Codification
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-Section S99
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Period end book value of accumulated depreciation on property, plant and equipment (PPE) that is owned by the regulated operations of the public utility.

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Period end amount of construction work in progress in public utility.

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Period end amount of total net PPE.

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Period end amount of total gross PPE.

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