Consolidated Statements of Cash Flows Statement (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income	$ 281	$ 256
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	317	305
Deferred income taxes and amortization of investment tax credits	170	136
Changes in regulatory assets and liabilities	(4)	(19)
Other, net	(18)	(15)
Changes in other operating assets and liabilities:
Accounts receivable and other assets	54	89
Derivative collateral, net	13	18
Inventories	(37)	(40)
Income taxes, net	130	287
Accounts payable and other liabilities	(24)	22
Net cash flows from operating activities	882	1,039
Cash flows from investing activities:
Capital expenditures	(721)	(712)
Other, net	(13)	2
Net cash flows from investing activities	(734)	(710)
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	(90)	(1)
Preferred stock dividends	(1)	(1)
Common stock dividends	(50)	(550)
Other, net	(8)	(2)
Net cash flows from financing activities	(88)	(191)
Net change in cash and cash equivalents	60	138
Cash and cash equivalents at beginning of period	47	31
Cash and cash equivalents at end of period	$ 107	$ 169