Consolidated Statements of Operations and Comprehensive Income (Unaudited) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Operating revenues [Abstract]
Total operating revenues	$ 6,082		$ 4,690
Operating expenses
Purchased power and fuel	2,981		1,765
Purchased power from affiliate	0		0
Operating and maintenance	1,764		1,968
Depreciation and amortization	543		382
Taxes other than income	277		194
Total operating expenses	5,565		4,309
Gain (loss) on equity method investments	(9)		(22)
Operating income	508		359
Other income and deductions
Interest expense	(617)		(189)
Interest expense to affiliates, net	(6)		(6)
Other, net	172		194
Total other income and deductions	(451)		(1)
Income before income taxes	57		358
Income taxes	56		158
Net income	1		200
Net income (loss) attributable to noncontrolling interests and preferred security dividends	(5)		0
Net income on common stock	(4)		200
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost	0		1
Actuarial loss reclassified to periodic cost	51		41
Transition obligation reclassified to periodic cost	0		1
Pension and non-pension postretirement benefit plans valuation adjustment	75		(8)
Change in unrealized gain (loss) on cash-flow hedges	(58)		215
Change in unrealized income (loss) on equity investments	28
Change in unrealized income (loss) on foreign currency translation	(1)
Change in unrealized gain (loss) on marketable securities	(1)		1
Other comprehensive income (loss)	94	[1]	251
Comprehensive income	95		451
Average shares of common stock outstanding:
Basic	855		705
Diluted	855		707
Earnings per average common share - basic
Net income	$ (0.01)		$ 0.28
Earnings per average common share - diluted
Net income	$ (0.01)		$ 0.28
Dividends per common share	$ 0.53		$ 0.53
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating revenues	3,141		2,373
Operating revenues from affiliates	392		370
Total operating revenues	3,533		2,743
Operating expenses
Purchased power	2,169		1,044
Purchased power from affiliate	0
Operating and maintenance	965		1,039
Operating and maintenance from affiliate	147		140
Depreciation and amortization	214		153
Taxes other than income	93		73
Total operating expenses	3,588		2,449
Gain (loss) on equity method investments	(9)		(22)
Operating income	(64)		272
Other income and deductions
Interest expense	(82)		(54)
Other, net	128		178
Total other income and deductions	46		124
Income before income taxes	(18)		396
Income taxes	(1)		230
Net income	(17)		166
Income (Loss) attributable to noncontrolling interest	(1)		2
Net income on membership interest	(18)		168
Pension and non-pension postretirement benefit plans:
Change in unrealized gain (loss) on cash-flow hedges	(130)		252
Change in unrealized income (loss) on equity investments	28
Change in unrealized income (loss) on foreign currency translation	(1)
Change in unrealized gain (loss) on marketable securities	(1)
Other comprehensive income (loss)	(104)	[1]	252
Comprehensive income	(121)		418
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Operating revenues	1,159		1,387
Operating revenues from affiliates	1		1
Total operating revenues	1,160		1,388
Operating expenses
Purchased power	237		373
Purchased power from affiliate	145		247
Operating and maintenance	292		276
Operating and maintenance from affiliate	36		42
Depreciation and amortization	167		149
Taxes other than income	74		75
Total operating expenses	951		1,162
Operating income	209		226
Other income and deductions
Interest expense	(350)		(79)
Interest expense to affiliates, net	(3)		(3)
Other, net	5		4
Total other income and deductions	(348)		(78)
Income before income taxes	(139)		148
Income taxes	(58)		61
Net income	(81)		87
Pension and non-pension postretirement benefit plans:
Change in unrealized gain (loss) on marketable securities	0		1
Other comprehensive income (loss)	0		1
Comprehensive income	(81)		88
PECO Energy Co [Member]
Operating revenues [Abstract]
Operating revenues	895		874
Operating revenues from affiliates	0		1
Total operating revenues	895		875
Operating expenses
Purchased power and fuel	265		300
Purchased power from affiliate	141		111
Operating and maintenance	164		173
Operating and maintenance from affiliate	24		30
Depreciation and amortization	57		53
Taxes other than income	41		31
Total operating expenses	692		698
Operating income	203		177
Other income and deductions
Interest expense	(26)		(28)
Interest expense to affiliates, net	(3)		(3)
Other, net	3		2
Total other income and deductions	(26)		(29)
Income before income taxes	177		148
Income taxes	55		51
Net income	122		97
Preferred security dividends	(1)		(1)
Net income on common stock	121		96
Pension and non-pension postretirement benefit plans:
Change in unrealized gain (loss) on cash-flow hedges	0		1
Other comprehensive income (loss)	0		1
Comprehensive income	122		98
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Operating revenues	876		694
Operating revenues from affiliates	4		3
Total operating revenues	880		697
Operating expenses
Purchased power and fuel	313		293
Purchased power from affiliate	113		92
Operating and maintenance	124		154
Operating and maintenance from affiliate	19		42
Depreciation and amortization	93		79
Taxes other than income	55		48
Total operating expenses	717		708
Operating income	163		(11)
Other income and deductions
Interest expense	(33)		(41)
Other, net	5		6
Total other income and deductions	(28)		(35)
Income before income taxes	135		(46)
Income taxes	55		(16)
Net income	80		(30)
Preferred security dividends	(3)		(3)
Net income on common stock	77		(33)
Pension and non-pension postretirement benefit plans:
Comprehensive income	$ 80		$ (30)

[1] (a) All amounts are net of tax. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.