Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2017

Balance Sheet Components [Abstract]

Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]

The following is the activity in the allowance for uncollectible accounts (in millions):

	Years Ended December 31,
	2017			2016			2015
Balance as of beginning of year	$	6		$	6		$	6
Increase in provision	6			5			6
Amounts written off, less recoveries	(6		)	(5		)	(6		)
Balance as of end of year	$	6		$	6		$	6

Investments held in trust [Table Text Block]

The trusts are comprised of the following investments as of December 31 (in millions):  

	Nuclear     Decommissioning Trust				Non-Qualified Benefit     Plan Trust
	2017		2016		2017		2016
Cash equivalents	$	25	$	21	$	1	$	1
Marketable securities, at fair value:
Equity securities	—		—		7		6
Debt securities	17		20		1		1
Insurance contracts, at cash surrender value	—		—		28		26
	$	42	$	41	$	37	$	34

Schedule of Other Assets and Other Liabilities [Table Text Block]

Other current assets and Accrued expenses and other current liabilities consist of the following (in millions):

	As of December 31,
	2017		2016
Other current assets:
Prepaid expenses	$	50	$	48
Margin deposits	11		8
Assets from price risk management activities	6		18
Other	6		3
	$	73	$	77
Accrued expenses and other current liabilities:
Regulatory liabilities—current	$	31	$	51
Accrued employee compensation and benefits	60		52
Accrued dividends payable	31		30
Accrued interest payable	27		25
Accrued taxes payable	31		25
Other	61		71
	$	241	$	254