Condensed Consolidating Statements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Operating revenues
Operating revenues	$ 2,273	$ 2,256	$ 4,365	$ 4,423
Affiliate revenues	0	0	0	0
Total revenues	2,273	2,256	4,365	4,423
Operating expenses
Fuel used in electric generation	736	674	1,421	1,392
Purchased power	257	329	467	549
Operation and maintenance	627	510	1,156	1,004
Depreciation, amortization and accretion	231	179	397	333
Taxes other than on income	142	134	280	274
Other	5	2	5	(8)
Total operating expenses	1,998	1,828	3,726	3,544
Operating (loss) income	275	428	639	879
Other income (expense)
Interest income	1	0	2	1
Allowance for equity funds used during construction	25	26	49	55
Other, net	1	7	14	10
Total other income (expense), net	27	33	65	66
Interest charges
Interest charges	203	189	397	388
Allowance for borrowed funds used during construction	(11)	(9)	(20)	(18)
Total interest charges, net	192	180	377	370
(Loss) income from continuing operations before income tax and equity in earnings of consolidated subsidiaries	110	281	327	575
Income tax (benefit) expense	42	101	118	208
Income from continuing operations	68	180	209	367
Discontinued operations, net of tax	(4)	(2)	7	(4)
Net income (loss)	64	178	216	363
Net income attributable to noncontrolling interests, net of tax	(1)	(2)	(3)	(3)
Net income attributable to controlling interests	63	176	213	360
Comprehensive income
Comprehensive income	60	157	217	346
Comprehensive (income) loss attributable to noncontrolling interests, net of tax	(1)	(2)	(3)	(3)
Comprehensive income attributable to controlling interests	59	155	214	343
ASSETS
Utility plant, net	23,192		23,192		22,497
Current assets
Cash and cash equivalents	73	52	73	52
Receivables, net	849		849		889
Notes receivable from affiliated companies	0		0		0
Regulatory assets	302		302		275
Derivative collateral posted	124		124		147
Prepayments and other current assets	2,039		2,039		1,942
Total current assets	3,387		3,387		3,483
Deferred debits and other assets
Investment in consolidated subsidiaries	0		0		0
Regulatory assets	2,954		2,954		3,025
Goodwill	3,655		3,655		3,655
Nuclear decommissioning trust funds	1,757		1,757		1,647
Other assets and deferred debits	779		779		752
Total deferred debits and other assets	9,145		9,145		9,079
Total assets	35,724		35,724		35,059
Equity
Common stock equity	9,897		9,897		10,021
Noncontrolling interests	3		3		4
Total equity	9,900	10,049	9,900	10,049	10,025	10,027
Preferred stock of subsidiaries	93		93		93
Long-term debt, affiliate	273		273		273
Long-term debt, net	12,739		12,739		11,718
Total capitalization	23,005		23,005		22,109
Current liabilities
Current portion of long-term debt	925		925		950
Short-term debt	345		345		671
Notes payable to affiliated companies	0		0		0
Derivative liabilities	326		326		436
Other current liabilities	1,974		1,974		2,028
Total current liabilities	3,570		3,570		4,085
Deferred credits and other liabilities
Noncurrent income tax liabilities	2,670		2,670		2,355
Regulatory liabilities	2,612		2,612		2,700
Other liabilities and deferred credits	3,867		3,867		3,810
Total deferred credits and other liabilities	9,149		9,149		8,865
Total capitalization and liabilities	35,724		35,724		35,059
Condensed Consolidating Statement of Cash Flows
Net cash provided (used) by operating activities			751	780
Investing activities
Gross property additions			(1,080)	(1,004)
Nuclear fuel additions			(65)	(93)
Purchases of available-for-sale securities and other investments			(625)	(3,387)
Proceeds from available-for-sale securities and other investments			610	3,364
Other investing activities			81	82
Net cash provided (used) by investing activities			(1,079)	(1,038)
Financing activities
Issuance of common stock, net			6	26
Dividends paid on common stock			(446)	(366)
Payments of short-term debt with original maturities greater than 90 days			(65)	0
Proceeds from issuance of short-term debt with original maturities greater than 90 days			65	0
Net increase (decrease) in short-term debt			(326)	314
Proceeds from issuance of long-term debt, net			1,432	494
Retirement of long-term debt			(450)	(700)
Other financing activities			(45)	(69)
Net cash provided (used) by financing activities			171	(301)
Net increase (decrease) in cash and cash equivalents			(157)	(559)
Cash and cash equivalents at beginning of period			230	611
Cash and cash equivalents at end of period	73	52	73	52
Parent
Operating revenues
Operating revenues	0	0	0	0
Affiliate revenues	0	0	0	0
Total revenues	0	0	0	0
Operating expenses
Fuel used in electric generation	0	0	0	0
Purchased power	0	0	0	0
Operation and maintenance	3	1	4	4
Depreciation, amortization and accretion	0	0	0	0
Taxes other than on income	0	0	0	0
Other	0	0	0	0
Total operating expenses	3	1	4	4
Operating (loss) income	(3)	(1)	(4)	(4)
Other income (expense)
Interest income	0	0	1	0
Allowance for equity funds used during construction	0	0	0	0
Other, net	0	4	8	4
Total other income (expense), net	0	4	9	4
Interest charges
Interest charges	64	63	130	136
Allowance for borrowed funds used during construction	0	0	0	0
Total interest charges, net	64	63	130	136
(Loss) income from continuing operations before income tax and equity in earnings of consolidated subsidiaries	(67)	(60)	(125)	(136)
Income tax (benefit) expense	(30)	(24)	(52)	(55)
Equity in earnings of consolidated subsidiaries	100	212	286	441
Income from continuing operations	63	176	213	360
Discontinued operations, net of tax	0	0	0	0
Net income (loss)	63	176	213	360
Net income attributable to noncontrolling interests, net of tax	0	0	0	0
Net income attributable to controlling interests	63	176	213	360
Comprehensive income
Comprehensive income	59	155	214	343
Comprehensive (income) loss attributable to noncontrolling interests, net of tax	0	0	0	0
Comprehensive income attributable to controlling interests	59	155	214	343
ASSETS
Utility plant, net	0		0		0
Current assets
Cash and cash equivalents	6	0	6	0
Receivables, net	0		0		0
Notes receivable from affiliated companies	62		62		53
Regulatory assets	0		0		0
Derivative collateral posted	0		0		0
Income taxes receivable					0
Prepayments and other current assets	137		137		128
Total current assets	205		205		298
Deferred debits and other assets
Investment in consolidated subsidiaries	13,871		13,871		14,043
Regulatory assets	0		0		0
Goodwill	0		0		0
Nuclear decommissioning trust funds	0		0		0
Other assets and deferred debits	115		115		140
Total deferred debits and other assets	13,986		13,986		14,183
Total assets	14,191		14,191		14,481
Equity
Common stock equity	9,897		9,897		10,021
Noncontrolling interests	0		0		0
Total equity	9,897		9,897		10,021
Preferred stock of subsidiaries	0		0		0
Long-term debt, affiliate	0		0		0
Long-term debt, net	3,992		3,992		3,543
Total capitalization	13,889		13,889		13,564
Current liabilities
Current portion of long-term debt	0		0		450
Short-term debt	201		201		250
Notes payable to affiliated companies	0		0		0
Derivative liabilities	0		0		38
Other current liabilities	78		78		161
Total current liabilities	279		279		899
Deferred credits and other liabilities
Noncurrent income tax liabilities	0		0		0
Regulatory liabilities	0		0		0
Other liabilities and deferred credits	23		23		18
Total deferred credits and other liabilities	23		23		18
Total capitalization and liabilities	14,191		14,191		14,481
Condensed Consolidating Statement of Cash Flows
Net cash provided (used) by operating activities			406	477
Investing activities
Gross property additions			0	0
Nuclear fuel additions			0	0
Proceeds from sales of assets to affiliated companies				0
Purchases of available-for-sale securities and other investments			0	0
Proceeds from available-for-sale securities and other investments			0	0
Changes in advances to affiliated companies			(9)	(80)
Return of investment in consolidated subsidiaries			0	0
Contributions to consolidated subsidiaries			0	(10)
Other investing activities			(13)	0
Net cash provided (used) by investing activities			(22)	(90)
Financing activities
Issuance of common stock, net			6	26
Dividends paid on common stock			(446)	(366)
Dividends paid to parent			0	0
Dividends paid to parent in excess of retained earnings			0	0
Payments of short-term debt with original maturities greater than 90 days			0	0
Proceeds from issuance of short-term debt with original maturities greater than 90 days			0
Net increase (decrease) in short-term debt			(49)	49
Proceeds from issuance of long-term debt, net			444	494
Retirement of long-term debt			(450)	(700)
Changes in advances from affiliated companies			0	0
Contributions from parent			0	0
Other financing activities			0	0
Net cash provided (used) by financing activities			(495)	(497)
Net increase (decrease) in cash and cash equivalents			(111)	(110)
Cash and cash equivalents at beginning of period			117	110
Cash and cash equivalents at end of period	6	0	6	0
Subsidiary Guarantor
Operating revenues
Operating revenues	1,191	1,196	2,198	2,230
Affiliate revenues	0	0	0	0
Total revenues	1,191	1,196	2,198	2,230
Operating expenses
Fuel used in electric generation	390	348	726	703
Purchased power	177	256	322	409
Operation and maintenance	246	223	406	434
Depreciation, amortization and accretion	92	48	119	73
Taxes other than on income	90	83	172	168
Other	4	2	4	(8)
Total operating expenses	999	960	1,749	1,779
Operating (loss) income	192	236	449	451
Other income (expense)
Interest income	1	0	1	1
Allowance for equity funds used during construction	8	8	17	17
Other, net	1	1	2	6
Total other income (expense), net	10	9	20	24
Interest charges
Interest charges	79	73	152	148
Allowance for borrowed funds used during construction	(5)	(3)	(9)	(7)
Total interest charges, net	74	70	143	141
(Loss) income from continuing operations before income tax and equity in earnings of consolidated subsidiaries	128	175	326	334
Income tax (benefit) expense	49	64	122	124
Equity in earnings of consolidated subsidiaries	0	0	0	0
Income from continuing operations	79	111	204	210
Discontinued operations, net of tax	(3)	(2)	8	(3)
Net income (loss)	76	109	212	207
Net income attributable to noncontrolling interests, net of tax	(1)	(1)	(2)	(2)
Net income attributable to controlling interests	75	108	210	205
Comprehensive income
Comprehensive income	76	103	213	202
Comprehensive (income) loss attributable to noncontrolling interests, net of tax	(1)	(1)	(2)	(2)
Comprehensive income attributable to controlling interests	75	102	211	200
ASSETS
Utility plant, net	10,710		10,710		10,523
Current assets
Cash and cash equivalents	33	33	33	33
Receivables, net	375		375		372
Notes receivable from affiliated companies	0		0		0
Regulatory assets	266		266		244
Derivative collateral posted	103		103		123
Income taxes receivable					0
Prepayments and other current assets	934		934		852
Total current assets	1,711		1,711		1,683
Deferred debits and other assets
Investment in consolidated subsidiaries	0		0		0
Regulatory assets	1,481		1,481		1,602
Goodwill	0		0		0
Nuclear decommissioning trust funds	593		593		559
Other assets and deferred debits	235		235		242
Total deferred debits and other assets	2,309		2,309		2,403
Total assets	14,730		14,730		14,609
Equity
Common stock equity	4,770		4,770		4,728
Noncontrolling interests	3		3		4
Total equity	4,773		4,773		4,732
Preferred stock of subsidiaries	34		34		34
Long-term debt, affiliate	309		309		309
Long-term debt, net	4,057		4,057		4,482
Total capitalization	9,173		9,173		9,557
Current liabilities
Current portion of long-term debt	425		425		0
Short-term debt	144		144		233
Notes payable to affiliated companies	447		447		238
Derivative liabilities	237		237		268
Other current liabilities	912		912		839
Total current liabilities	2,165		2,165		1,578
Deferred credits and other liabilities
Noncurrent income tax liabilities	1,006		1,006		837
Regulatory liabilities	905		905		1,071
Other liabilities and deferred credits	1,481		1,481		1,566
Total deferred credits and other liabilities	3,392		3,392		3,474
Total capitalization and liabilities	14,730		14,730		14,609
Condensed Consolidating Statement of Cash Flows
Net cash provided (used) by operating activities			368	413
Investing activities
Gross property additions			(380)	(419)
Nuclear fuel additions			(15)	(13)
Proceeds from sales of assets to affiliated companies				0
Purchases of available-for-sale securities and other investments			(354)	(3,093)
Proceeds from available-for-sale securities and other investments			354	3,095
Changes in advances to affiliated companies			0	22
Return of investment in consolidated subsidiaries			0	0
Contributions to consolidated subsidiaries			0	0
Other investing activities			25	74
Net cash provided (used) by investing activities			(370)	(334)
Financing activities
Issuance of common stock, net			0	0
Dividends paid on common stock			0	0
Dividends paid to parent			(173)	(403)
Dividends paid to parent in excess of retained earnings			0	0
Payments of short-term debt with original maturities greater than 90 days			(65)	0
Proceeds from issuance of short-term debt with original maturities greater than 90 days			65
Net increase (decrease) in short-term debt			(89)	67
Proceeds from issuance of long-term debt, net			0	0
Retirement of long-term debt			0	0
Changes in advances from affiliated companies			209	16
Contributions from parent			0	10
Other financing activities			(4)	(6)
Net cash provided (used) by financing activities			(57)	(316)
Net increase (decrease) in cash and cash equivalents			(59)	(237)
Cash and cash equivalents at beginning of period			92	270
Cash and cash equivalents at end of period	33	33	33	33
Non-Guarantor Subsidiaries
Operating revenues
Operating revenues	1,082	1,060	2,167	2,193
Affiliate revenues	72	61	131	135
Total revenues	1,154	1,121	2,298	2,328
Operating expenses
Fuel used in electric generation	346	326	695	689
Purchased power	80	73	145	140
Operation and maintenance	448	343	870	694
Depreciation, amortization and accretion	139	131	278	260
Taxes other than on income	54	51	112	110
Other	2	0	2	0
Total operating expenses	1,069	924	2,102	1,893
Operating (loss) income	85	197	196	435
Other income (expense)
Interest income	0	0	0	0
Allowance for equity funds used during construction	17	18	32	38
Other, net	1	0	3	(2)
Total other income (expense), net	18	18	35	36
Interest charges
Interest charges	60	53	115	104
Allowance for borrowed funds used during construction	(6)	(6)	(11)	(11)
Total interest charges, net	54	47	104	93
(Loss) income from continuing operations before income tax and equity in earnings of consolidated subsidiaries	49	168	127	378
Income tax (benefit) expense	18	60	45	140
Equity in earnings of consolidated subsidiaries	0	0	0	0
Income from continuing operations	31	108	82	238
Discontinued operations, net of tax	(1)	0	(1)	(1)
Net income (loss)	30	108	81	237
Net income attributable to noncontrolling interests, net of tax	0	0	0	0
Net income attributable to controlling interests	30	108	81	237
Comprehensive income
Comprehensive income	25	96	80	228
Comprehensive (income) loss attributable to noncontrolling interests, net of tax	0	0	0	0
Comprehensive income attributable to controlling interests	25	96	80	228
ASSETS
Utility plant, net	12,398		12,398		11,887
Current assets
Cash and cash equivalents	34	19	34	19
Receivables, net	474		474		517
Notes receivable from affiliated companies	388		388		219
Regulatory assets	36		36		31
Derivative collateral posted	21		21		24
Income taxes receivable					0
Prepayments and other current assets	1,099		1,099		1,049
Total current assets	2,052		2,052		1,861
Deferred debits and other assets
Investment in consolidated subsidiaries	0		0		0
Regulatory assets	1,473		1,473		1,423
Goodwill	0		0		0
Nuclear decommissioning trust funds	1,164		1,164		1,088
Other assets and deferred debits	875		875		856
Total deferred debits and other assets	3,512		3,512		3,367
Total assets	17,962		17,962		17,115
Equity
Common stock equity	5,432		5,432		5,646
Noncontrolling interests	0		0		0
Total equity	5,432		5,432		5,646
Preferred stock of subsidiaries	59		59		59
Long-term debt, affiliate	0		0		0
Long-term debt, net	4,690		4,690		3,693
Total capitalization	10,181		10,181		9,398
Current liabilities
Current portion of long-term debt	500		500		500
Short-term debt	0		0		188
Notes payable to affiliated companies	3		3		34
Derivative liabilities	89		89		130
Other current liabilities	1,117		1,117		1,112
Total current liabilities	1,709		1,709		1,964
Deferred credits and other liabilities
Noncurrent income tax liabilities	2,084		2,084		1,976
Regulatory liabilities	1,622		1,622		1,543
Other liabilities and deferred credits	2,366		2,366		2,234
Total deferred credits and other liabilities	6,072		6,072		5,753
Total capitalization and liabilities	17,962		17,962		17,115
Condensed Consolidating Statement of Cash Flows
Net cash provided (used) by operating activities			458	567
Investing activities
Gross property additions			(700)	(585)
Nuclear fuel additions			(50)	(80)
Proceeds from sales of assets to affiliated companies				0
Purchases of available-for-sale securities and other investments			(271)	(294)
Proceeds from available-for-sale securities and other investments			256	269
Changes in advances to affiliated companies			(169)	40
Return of investment in consolidated subsidiaries			0	0
Contributions to consolidated subsidiaries			0	0
Other investing activities			70	8
Net cash provided (used) by investing activities			(864)	(642)
Financing activities
Issuance of common stock, net			0	0
Dividends paid on common stock			0	0
Dividends paid to parent			(310)	(275)
Dividends paid to parent in excess of retained earnings			0	0
Payments of short-term debt with original maturities greater than 90 days			0	0
Proceeds from issuance of short-term debt with original maturities greater than 90 days			0
Net increase (decrease) in short-term debt			(188)	198
Proceeds from issuance of long-term debt, net			988	0
Retirement of long-term debt			0	0
Changes in advances from affiliated companies			(31)	3
Contributions from parent			0	0
Other financing activities			(40)	(63)
Net cash provided (used) by financing activities			419	(137)
Net increase (decrease) in cash and cash equivalents			13	(212)
Cash and cash equivalents at beginning of period			21	231
Cash and cash equivalents at end of period	34	19	34	19
Other
Operating revenues
Operating revenues	0	0	0	0
Affiliate revenues	(72)	(61)	(131)	(135)
Total revenues	(72)	(61)	(131)	(135)
Operating expenses
Fuel used in electric generation	0	0	0	0
Purchased power	0	0	0	0
Operation and maintenance	(70)	(57)	(124)	(128)
Depreciation, amortization and accretion	0	0	0	0
Taxes other than on income	(2)	0	(4)	(4)
Other	(1)	0	(1)	0
Total operating expenses	(73)	(57)	(129)	(132)
Operating (loss) income	1	(4)	(2)	(3)
Other income (expense)
Interest income	0	0	0	0
Allowance for equity funds used during construction	0	0	0	0
Other, net	(1)	2	1	2
Total other income (expense), net	(1)	2	1	2
Interest charges
Interest charges	0	0	0	0
Allowance for borrowed funds used during construction	0	0	0	0
Total interest charges, net	0	0	0	0
(Loss) income from continuing operations before income tax and equity in earnings of consolidated subsidiaries	0	(2)	(1)	(1)
Income tax (benefit) expense	5	1	3	(1)
Equity in earnings of consolidated subsidiaries	(100)	(212)	(286)	(441)
Income from continuing operations	(105)	(215)	(290)	(441)
Discontinued operations, net of tax	0	0	0	0
Net income (loss)	(105)	(215)	(290)	(441)
Net income attributable to noncontrolling interests, net of tax	0	(1)	(1)	(1)
Net income attributable to controlling interests	(105)	(216)	(291)	(442)
Comprehensive income
Comprehensive income	(100)	(197)	(290)	(427)
Comprehensive (income) loss attributable to noncontrolling interests, net of tax	0	(1)	(1)	(1)
Comprehensive income attributable to controlling interests	(100)	(198)	(291)	(428)
ASSETS
Utility plant, net	84		84		87
Current assets
Cash and cash equivalents	0	0	0	0
Receivables, net	0		0		0
Notes receivable from affiliated companies	(450)		(450)		(272)
Regulatory assets	0		0		0
Derivative collateral posted	0		0		0
Income taxes receivable					0
Prepayments and other current assets	(131)		(131)		(87)
Total current assets	(581)		(581)		(359)
Deferred debits and other assets
Investment in consolidated subsidiaries	(13,871)		(13,871)		(14,043)
Regulatory assets	0		0		0
Goodwill	3,655		3,655		3,655
Nuclear decommissioning trust funds	0		0		0
Other assets and deferred debits	(446)		(446)		(486)
Total deferred debits and other assets	(10,662)		(10,662)		(10,874)
Total assets	(11,159)		(11,159)		(11,146)
Equity
Common stock equity	(10,202)		(10,202)		(10,374)
Noncontrolling interests	0		0		0
Total equity	(10,202)		(10,202)		(10,374)
Preferred stock of subsidiaries	0		0		0
Long-term debt, affiliate	(36)		(36)		(36)
Long-term debt, net	0		0		0
Total capitalization	(10,238)		(10,238)		(10,410)
Current liabilities
Current portion of long-term debt	0		0		0
Short-term debt	0		0		0
Notes payable to affiliated companies	(450)		(450)		(272)
Derivative liabilities	0		0		0
Other current liabilities	(133)		(133)		(84)
Total current liabilities	(583)		(583)		(356)
Deferred credits and other liabilities
Noncurrent income tax liabilities	(420)		(420)		(458)
Regulatory liabilities	85		85		86
Other liabilities and deferred credits	(3)		(3)		(8)
Total deferred credits and other liabilities	(338)		(338)		(380)
Total capitalization and liabilities	(11,159)		(11,159)		(11,146)
Condensed Consolidating Statement of Cash Flows
Net cash provided (used) by operating activities			(481)	(677)
Investing activities
Gross property additions			0	0
Nuclear fuel additions			0	0
Proceeds from sales of assets to affiliated companies				0
Purchases of available-for-sale securities and other investments			0	0
Proceeds from available-for-sale securities and other investments			0	0
Changes in advances to affiliated companies			178	18
Return of investment in consolidated subsidiaries			0	0
Contributions to consolidated subsidiaries			0	10
Other investing activities			(1)	0
Net cash provided (used) by investing activities			177	28
Financing activities
Issuance of common stock, net			0	0
Dividends paid on common stock			0	0
Dividends paid to parent			483	678
Dividends paid to parent in excess of retained earnings			0	0
Payments of short-term debt with original maturities greater than 90 days			0	0
Proceeds from issuance of short-term debt with original maturities greater than 90 days			0
Net increase (decrease) in short-term debt			0	0
Proceeds from issuance of long-term debt, net			0	0
Retirement of long-term debt			0	0
Changes in advances from affiliated companies			(178)	(19)
Contributions from parent			0	(10)
Other financing activities			(1)	0
Net cash provided (used) by financing activities			304	649
Net increase (decrease) in cash and cash equivalents			0	0
Cash and cash equivalents at beginning of period			0	0
Cash and cash equivalents at end of period	$ 0	$ 0	$ 0	$ 0