Consolidated Statements of Cash Flows Statement (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 160	$ 151
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	168	157
Deferred income taxes and amortization of investment tax credits	51	89
Changes in regulatory assets and liabilities	(7)	0
Other, net	(10)	(11)
Changes in other operating assets and liabilities:
Accounts receivable and other assets	110	82
Derivative collateral, net	22	85
Inventories	(10)	(23)
Income taxes, net	(32)	(17)
Accounts payable and other liabilities	17	(34)
Net cash flows from operating activities	469	479
Cash flows from investing activities:
Capital expenditures	(259)	(405)
Other, net	6	9
Net cash flows from investing activities	(253)	(396)
Cash flows from financing activities:
Net repayments of short-term debt	0	(688)
Proceeds from long-term debt	0	749
Repayments and redemptions of long-term debt and capital lease obligations	(11)	(90)
Common stock dividends	(150)	(50)
Preferred stock dividends	(1)	(1)
Other, net	(1)	(5)
Net cash flows from financing activities	(163)	(85)
Net change in cash and cash equivalents	53	(2)
Cash and cash equivalents at beginning of period	80	47
Cash and cash equivalents at end of period	$ 133	$ 45