Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net income	$ 1,352	$ 1,310	$ 1,188
Adjustments to reconcile net income to net cash flows from operating activities:
Loss (gain) on other items, net	50	(39)	11
Depreciation and amortization	1,341	1,276	1,256
Stock-based compensation	0	0	123
Changes in regulatory assets and liabilities	(12)	20	23
Deferred income taxes and amortization of investment tax credits	937	854	864
Other, net	(66)	(55)	(45)
Changes in other operating assets and liabilities:
Trade receivables and other assets	(139)	(44)	17
Derivative collateral, net	(8)	(96)	81
Trading securities	0	0	499
Contributions to pension and other postretirement benefit plans, net	(133)	(139)	(82)
Accrued property, income and other taxes	(53)	(332)	(296)
Accounts payable and other liabilities	(49)	4	(67)
Net cash flows from operating activities	3,220	2,759	3,572
Cash flows from investing activities:
Capital expenditures	(2,684)	(2,593)	(3,413)
Purchases of available-for-sale securities	(123)	(106)	(499)
Proceeds from sales of available-for-sale securities	111	100	256
Proceeds from Constellation Energy Group, Inc. 14% note	0	0	1,000
Proceeds from sales of assets and business, net	10	146	13
Equity method investments	(124)	(66)	(34)
(Increase) decrease in restricted cash and other	(6)	35	8
Net cash flows from investing activities	(2,816)	(2,484)	(2,669)
Cash flows from financing activities:
Proceeds from MEHC senior debt	0	0	250
Repayments of MEHC subordinated debt	(334)	(281)	(734)
Proceeds from subsidiary debt	790	231	992
Repayments of subsidiary debt	(1,548)	(192)	(444)
Net proceeds from (repayments of) short-term debt	545	149	(664)
Net purchases of common stock	0	(56)	(123)
Net payments to noncontrolling interests	(24)	(80)	(19)
Other, net	(18)	(5)	(16)
Net cash flows from financing activities	(589)	(234)	(758)
Effect of exchange rate changes	1	0	4
Net change in cash and cash equivalents	(184)	41	149
Cash and cash equivalents at beginning of period	470	429	280
Cash and cash equivalents at end of period	$ 286	$ 470	$ 429