Consolidated Statements of Cash Flows Statement (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities:
Net income	$ 493	$ 425
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	478	456
Deferred income taxes and amortization of investment tax credits	268	274
Changes in regulatory assets and liabilities	(27)	(23)
Other, net	(26)	(21)
Changes in other operating assets and liabilities:
Accounts receivable and other assets	(5)	(8)
Derivative collateral, net	56	44
Inventories	(37)	(34)
Income taxes, net	159	333
Accounts payable and other liabilities	(4)	6
Net cash flows from operating activities	1,355	1,452
Cash flows from investing activities:
Capital expenditures	(1,037)	(1,069)
Other, net	0	2
Net cash flows from investing activities	(1,037)	(1,067)
Cash flows from financing activities:
Net repayments of short-term debt	(688)	(36)
Proceeds from long-term debt	749	399
Repayments and redemptions of long-term debt and capital lease obligations	(91)	(74)
Preferred stock dividends	(2)	(2)
Common stock dividends	(150)	(550)
Other, net	(8)	(2)
Net cash flows from financing activities	(190)	(265)
Net change in cash and cash equivalents	128	120
Cash and cash equivalents at beginning of period	47	31
Cash and cash equivalents at end of period	$ 175	$ 151