Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$ 698us-gaap_NetIncomeLoss	$ 682us-gaap_NetIncomeLoss	$ 537us-gaap_NetIncomeLoss
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	726	675	640
Allowance for equity funds	(51)	(57)	(58)
Deferred income taxes and amortization of investment tax credits	297	230	312
Changes in regulatory assets and liabilities	(112)	(32)	1
Other, net	22us-gaap_OtherNoncashIncomeExpense	21us-gaap_OtherNoncashIncomeExpense	26us-gaap_OtherNoncashIncomeExpense
Changes in other operating assets and liabilities:
Accounts receivable and other assets	5	(7)	(17)
Derivative collateral, net	(16)	43	68
Inventories	37us-gaap_IncreaseDecreaseInInventories	14us-gaap_IncreaseDecreaseInInventories	(35)us-gaap_IncreaseDecreaseInInventories
Income taxes, net	(155)	(26)	118
Accounts payable and other liabilities	119	10	35
Net cash flows from operating activities	1,570	1,553	1,627
Cash flows from investing activities:
Capital expenditures	(1,066)	(1,065)	(1,346)
Other, net	(13)	16	4
Net cash flows from investing activities	(1,079)	(1,049)	(1,342)
Cash flows from financing activities:
Proceeds from long-term debt	425	299	749
Repayments of long-term debt and capital lease obligations	(238)	(284)	(102)
Net proceeds from (repayments of) short-term debt	20	0	(688)
Redemption of preferred stock	0	(40)	0
Common stock dividends	(725)us-gaap_PaymentsOfDividendsCommonStock	(500)us-gaap_PaymentsOfDividendsCommonStock	(200)us-gaap_PaymentsOfDividendsCommonStock
Preferred stock dividends	0	(2)	(2)
Other, net	(3)	(4)	(9)
Net cash flows from financing activities	(521)	(531)	(252)
Net change in cash and cash equivalents	(30)	(27)	33
Cash and cash equivalents at beginning of period	53	80	47
Cash and cash equivalents at end of period	$ 23	$ 53	$ 80

The increase (decrease) during the reporting period in cash placed with or received from a broker or counterparty.

No definition available.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.

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Amount of deferred income tax expense (benefit) and income tax credits.

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The increase (decrease) during the reporting period in the aggregate amount of obligations incurred but not paid and other operating obligations not separately disclosed in the statement of cash flows.

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No definition available.

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The increase (decrease) during the reporting period in the total amount of receivables from all parties and other operating assets not separately disclosed in the statement of cash flows.

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The increase (decrease) during the reporting period in the capitalized cost of equity (based on assumed rate of return) and / or borrowed funds (based on interest rate) used to finance construction of regulated assets, which is expected to be recovered through rate adjustments. As a result of this capitalization, net income is increased. This element pertains to certain regulated industries, such as public utilities.

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The increase (decrease) during the reporting period in the amounts payable to taxing authorities for taxes that are based on the reporting entity's earnings, net of amounts receivable from taxing authorities for refunds of overpayments or recoveries of income taxes.

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The increase (decrease) during the reporting period in the aggregate value of all inventory held by the reporting entity, associated with underlying transactions that are classified as operating activities.

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The increase (decrease) during the reporting period in the value of assets that are created when regulatory agencies permits public utilities to defer costs (revenues) to the balance sheet. This element is a the increase (decrease) of regulatory assets and liabilities combined.

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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

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Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Other income (expense) included in net income that results in no cash inflows or outflows in the period. Includes noncash adjustments to reconcile net income (loss) to cash provided by (used in) operating activities that are not separately disclosed.

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The net cash outflow or inflow from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.

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The cash outflow for reacquisition of callable preferred stock.

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Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.

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Amount of cash outflow in the form of ordinary dividends to preferred shareholders of the parent entity.

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The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

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The cash inflow from amounts received from a long-term debt instrument secured by a first mortgage deed of trust, containing a pledge of real property. The lender has the highest claim on the property in case of default.

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The net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.

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The net cash inflow or outflow for borrowing having initial term of repayment within one year or the normal operating cycle, if longer.

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The cash outflow associated with security instruments that either represent a creditor or an ownership relationship with the holder of the investment security with a maturity of beyond one year or normal operating cycle, if longer. Includes repayments of (a) debt, (b) capital lease obligations, (c) mandatory redeemable capital securities, and (d) any combination of (a), (b), or (c).

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Amount of operating expense for depreciation and amortization of regulated operation.

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