Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2015

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,
	2015			2014			2013
Balance as of beginning of year	$	6		$	6		$	5
Increase in provision	6			6			6
Amounts written off, less recoveries	(6		)	(6		)	(5		)
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
	2015		2014		2015		2014
Cash equivalents	$	18	$	65	$	1	$	—
Marketable securities, at fair value:
Equity securities	—		—		5		6
Debt securities	22		25		1		—
Insurance contracts, at cash surrender value	—		—		26		26
	$	40	$	90	$	33	$	32

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,
	2015		2014
Other current assets:
Prepaid expenses	$	43	$	39
Current deferred income tax asset	—		33
Accrued sales tax refund related to Tucannon River Wind Farm	—		23
Margin deposits	33		11
Assets from price risk management activities	10		6
Other	2		3
	$	88	$	115
Accrued expenses and other current liabilities:
Regulatory liabilities—current	$	55	$	60
Accrued employee compensation and benefits	51		51
Accrued interest payable	25		26
Accrued dividends payable	28		23
Accrued taxes payable	25		22
Other	75		54
	$	259	$	236