Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net income	$ 140	$ 147	$ 121
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	248	227	238
Deferred income taxes	47	56	67
Renewable adjustment clause deferrals	1	22	(12)
Pension and other postretirement benefits	27	15	11
Regulatory deferral of settled derivative instruments	(9)	12	26
Power cost deferrals, net of amortization	(4)	10	(1)
Increase (decrease) in net liabilities from price risk management activities	(175)	9	118
Regulatory deferrals--price risk management activities	172	(6)	(118)
Allowance for equity funds used during construction	(6)	(5)	(13)
Decoupling mechanism deferrals, net of amortization	2	3	(10)
Unrealized gains on non-qualified benefit plan trust assets	3	0	(5)
Other non-cash income and expenses, net	16	16	3
Changes in working capital:
(Increase) decrease in receivables and unbilled revenues	(4)	(15)	24
Decrease (increase) in margin deposits	34	3	(27)
Income tax refund received	8	9	53
Increase in income taxes receivable	0	0	(22)
Increase (decrease) in payables and accrued liabilities	1	5	(11)
Other working capital items, net	1	(7)	0
Contribution to pension plan	0	(26)	(30)
Contribution to voluntary employees’ benefit association trust	(2)	(16)	(1)
Other, net	(6)	(6)	(20)
Net cash provided by operating activities	494	453	391
Cash flows from investing activities:
Capital expenditures	(303)	(300)	(450)
Purchases of nuclear decommissioning trust securities	(26)	(50)	(46)
Sales of nuclear decommissioning trust securities	23	46	50
Distribution from nuclear decommissioning fund	0	0	19
Proceeds from Sale of Productive Assets	10	0	0
Other, net	2	5	(3)
Net cash used in investing activities	(294)	(299)	(430)
Cash flows from financing activities:
Proceeds from issuance of long-term debt	0	0	249
Payments on long-term debt	(100)	(73)	(186)
Issuances (maturities) of commercial paper, net	13	(11)	(19)
Borrowings on short-term debt	0	0	11
Payments on short-term debt	0	0	(11)
Dividends paid	(81)	(79)	(78)
Premium paid on repayment of long-term debt	0	(7)	0
Debt issuance costs	0	0	(2)
Noncontrolling interests’ capital (distributions) contributions	0	(4)	10
Net cash (used in) provided by financing activities	(194)	(152)	12
Change in cash and cash equivalents	6	2	(27)
Cash and cash equivalents, beginning of year	6	4	31
Cash and cash equivalents, end of year	12	6	4
Supplemental disclosures of cash flow information:
Cash paid for interest, net of amounts capitalized	97	103	98
Cash paid for income taxes	13	3	0
Non-cash investing and financing activities:
Accrued capital additions	19	19	12
Accrued dividends payable	21	21	20
Preliminary engineering transferred to Construction work in progress from Other noncurrent assets	$ 0	$ 7	$ 0