Balance Sheet Components Asset Retirement Obligations (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Asset Retirement Obligation Disclosure [Abstract]
Trojan decommissioning activities	$ 69	$ 45
Utility plant	111	109
Non-utility property	16	13
Asset Retirement Obligations	$ 196	$ 167

The estimated amount of costs required as of the balance sheet date to comply with regulatory requirements pertaining to the retirement of a waste management facility, which will be paid after one year or beyond the normal operating cycle, if longer.

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The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Noncurrent portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Amount of a decommissioning liability associated with a legal obligation that a firm incurs when it constructs or operates an asset that must eventually be withdrawn from active service. This may include operating assets such as nuclear power plants or shipping vessels.

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