Consolidated Statements of Operations and Comprehensive Income (Unaudited) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Operating revenues [Abstract]
Total operating revenues	$ 4,686,000,000	$ 4,956,000,000
Operating expenses
Purchased power and fuel	1,765,000,000	2,001,000,000
Purchased power from affiliate	0	0
Operating and maintenance	1,964,000,000	1,223,000,000
Depreciation and amortization	382,000,000	327,000,000
Taxes other than income	194,000,000	203,000,000
Total operating expenses	4,305,000,000	3,754,000,000
Gain (loss) on equity method investments	(22,000,000)	0
Operating income	359,000,000	1,202,000,000
Other income and deductions
Interest expense, net	(189,000,000)	(175,000,000)
Interest expense to affiliates, net	(6,000,000)	(6,000,000)
Other, net	194,000,000	94,000,000
Total other income and deductions	(1,000,000)	(87,000,000)
Income from continuing operations before income taxes	358,000,000	1,115,000,000
Income taxes	158,000,000	446,000,000
Net income	200,000,000	669,000,000
Net income (loss) attributable to noncontrolling interests and preferred security dividends	0	1,000,000
Net income on common stock	200,000,000	668,000,000
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost	1,000,000	(1,000,000)
Actuarial loss reclassified to periodic cost	41,000,000	33,000,000
Transition obligation reclassified to periodic cost	1,000,000	1,000,000
Pension and non-pension postretirement benefit plans valuation adjustment	(8,000,000)	39,000,000
Change in unrealized gain (loss) on cash-flow hedges	215,000,000	(46,000,000)
Change in unrealized gain (loss) on marketable securities	1,000,000	0
Other comprehensive income (loss)		26,000,000
Comprehensive income	451,000,000	694,000,000
Average shares of common stock outstanding:
Basic	705,000,000	662,000,000
Diluted	707,000,000	664,000,000
Earnings per average common share - basic
Net income	$ 0.28	$ 1.01
Earnings per average common share - diluted
Net income	$ 0.28	$ 1.01
Dividends per common share	$ 0.53	$ 0.53
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating revenues	2,373,000,000	2,337,000,000
Operating revenues from affiliates	366,000,000	306,000,000
Total operating revenues	2,739,000,000	2,643,000,000
Operating expenses
Purchased power	1,044,000,000	883,000,000
Operating and maintenance	1,039,000,000	680,000,000
Operating and maintenance from affiliate	136,000,000	74,000,000
Depreciation and amortization	153,000,000	139,000,000
Taxes other than income	73,000,000	66,000,000
Total operating expenses	2,445,000,000	1,842,000,000
Gain (loss) on equity method investments	(22,000,000)	0
Operating income	272,000,000	801,000,000
Other income and deductions
Interest expense, net	(54,000,000)	(45,000,000)
Other, net	178,000,000	75,000,000
Total other income and deductions	124,000,000	30,000,000
Income from continuing operations before income taxes	396,000,000	831,000,000
Income taxes	230,000,000	336,000,000
Net income	166,000,000	495,000,000
Net income (loss) attributable to noncontrolling interests and preferred security dividends	(2,000,000)	0
Net income on common stock	168,000,000	495,000,000
Pension and non-pension postretirement benefit plans:
Change in unrealized gain (loss) on cash-flow hedges	252,000,000	(70,000,000)
Other comprehensive income (loss)	252,000,000	(70,000,000)
Comprehensive income	420,000,000	425,000,000
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Operating revenues	1,387,000,000	1,465,000,000
Operating revenues from affiliates	1,000,000	1,000,000
Total operating revenues	1,388,000,000	1,466,000,000
Operating expenses
Purchased power	373,000,000	626,000,000
Purchased power from affiliate	247,000,000	163,000,000
Operating and maintenance	276,000,000	229,000,000
Operating and maintenance from affiliate	42,000,000	37,000,000
Depreciation and amortization	149,000,000	134,000,000
Taxes other than income	75,000,000	77,000,000
Total operating expenses	1,162,000,000	1,266,000,000
Operating income	226,000,000	200,000,000
Other income and deductions
Interest expense, net	(79,000,000)	(82,000,000)
Interest expense to affiliates, net	(3,000,000)	(3,000,000)
Other, net	4,000,000	4,000,000
Total other income and deductions	(78,000,000)	(81,000,000)
Income from continuing operations before income taxes	148,000,000	119,000,000
Income taxes	61,000,000	50,000,000
Net income	87,000,000	69,000,000
Pension and non-pension postretirement benefit plans:
Change in unrealized gain (loss) on marketable securities	1,000,000	0
Other comprehensive income (loss)	1,000,000	0
Comprehensive income	88,000,000	69,000,000
PECO Energy Co [Member]
Operating revenues [Abstract]
Operating revenues	874,000,000	1,152,000,000
Operating revenues from affiliates	1,000,000	1,000,000
Total operating revenues	875,000,000	1,153,000,000
Operating expenses
Purchased power and fuel	300,000,000	492,000,000
Purchased power from affiliate	111,000,000	141,000,000
Operating and maintenance	173,000,000	184,000,000
Operating and maintenance from affiliate	30,000,000	22,000,000
Depreciation and amortization	53,000,000	48,000,000
Taxes other than income	31,000,000	56,000,000
Total operating expenses	698,000,000	943,000,000
Operating income	177,000,000	210,000,000
Other income and deductions
Interest expense, net	(28,000,000)	(31,000,000)
Interest expense to affiliates, net	(3,000,000)	(3,000,000)
Other, net	2,000,000	6,000,000
Total other income and deductions	(29,000,000)	(28,000,000)
Income from continuing operations before income taxes	148,000,000	182,000,000
Income taxes	51,000,000	56,000,000
Net income	97,000,000	126,000,000
Preferred security dividends	(1,000,000)	(1,000,000)
Net income on common stock	96,000,000	125,000,000
Pension and non-pension postretirement benefit plans:
Change in unrealized gain (loss) on cash-flow hedges	1,000,000	0
Comprehensive income	98,000,000	126,000,000
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Operating revenues	693,000,000	975,000,000
Operating revenues from affiliates	3,000,000	1,000,000
Total operating revenues	696,000,000	976,000,000
Operating expenses
Purchased power and fuel	293,000,000	487,000,000
Purchased power from affiliate	92,000,000	57,000,000
Operating and maintenance	153,000,000	120,000,000
Operating and maintenance from affiliate	42,000,000	32,000,000
Depreciation and amortization	79,000,000	77,000,000
Taxes other than income	48,000,000	50,000,000
Total operating expenses	707,000,000	823,000,000
Gain (loss) on equity method investments	0	0
Operating income	(11,000,000)	153,000,000
Other income and deductions
Interest expense, net	(41,000,000)	(33,000,000)
Interest expense to affiliates, net	0	0
Other, net	6,000,000	8,000,000
Total other income and deductions	(35,000,000)	(25,000,000)
Income from continuing operations before income taxes	(46,000,000)	128,000,000
Income taxes	(16,000,000)	47,000,000
Net income	(30,000,000)	81,000,000
Preferred security dividends	(3,000,000)	(3,000,000)
Net income on common stock	(33,000,000)	78,000,000
Pension and non-pension postretirement benefit plans:
Comprehensive income	$ (30,000,000)	$ 81,000,000