Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Expenses related to Cascade Crossing	$ 52	$ 0	$ 0
Business days after the invoice date	16
Days after the due date	45
Wholesale accounts receivable written off	0	0	0
Other Investments	104	0
Margin deposit	9	46
Letters of Credit Outstanding, Amount	29	45
Public Utilities, Allowance for Funds Used During Construction, Rate	7.50%	7.50%	7.80%
Public Utilities, Allowance for Funds Used During Construction, Capitalized Interest	7	4	3
Allowance for equity funds used during construction	13	6	5
Depreciation expense rate	3.70%	3.80%	3.70%
Asset Retirement Removal Costs Included in Depreciation Expense	55	55	49
Finite-Lived Intangible Assets, Accumulated Amortization	170	151
Amortization of Intangible Assets	22	22	19
Future Amortization Expense, Year One	23
Future Amortization Expense, Year Two	22
Future Amortization Expense, Year Three	19
Future Amortization Expense, Year Four	16
Future Amortization Expense, Year Five	14
Power Cost Deadband - Lower Threshold	15
Power Cost Deadband - Upper Threshold	30
Net variable power cost overrun	11
Net Variable Power Cost Underrun		17	34
Estimated Refund Under Power Cost Adjustment Mechanism	0	0	(10)
Potential Refund Under the PCAM		17
Actual Refund Under Power Cost Adjustment Mechanism		0	(6)
Franchise taxes	41	42	41
Deferred Tax Assets, Regulatory Assets and Liabilities	16	20
Noncurrent Regulatory Assets [Member]
Property, Plant and Equipment [Line Items]
Deferred Tax Assets, Regulatory Assets and Liabilities	$ 76	$ 80