Consolidated Statements of Operations and Comprehensive Income (Unaudited) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating revenues [Abstract]
Operating revenues from affiliates	$ 48.00	$ 9.00	$ 6.00
Total operating revenues	23,489.00	19,063.00	18,644.00
Operating expenses
Purchased power	10,157.00	7,267.00	6,435.00
Operating and maintenance	7,961.00	5,184.00	4,600.00
Operating and maintenance for regulatory required programs
Depreciation and amortization	1,881.00	1,347.00	2,075.00
Taxes other than income	1,019.00	785.00	808.00
Total operating expenses	21,018.00	14,583.00	13,918.00
Gain (loss) on equity method investments	(91.00)	(1.00)	0
Operating income	2,380.00	4,479.00	4,726.00
Other income and deductions
Interest expense	(903.00)	(701.00)	(792.00)
Interest expense to affiliates, net	(25.00)	(25.00)	(25.00)
Other, net	346.00	203.00	312.00
Total other income and deductions	(582.00)	(523.00)	(505.00)
Income before income taxes	1,798.00	3,956.00	4,221.00
Income taxes	627.00	1,457.00	1,658.00
Income from continuing operations
Discontinued operations
Income from discontinued operations, net
Net income	1,171.00	2,499.00	2,563.00
Net income (loss) attributable to noncontrolling interests and preferred security dividends	(11.00)	(4.00)	0
Net income on common stock	1,160.00	2,495.00	2,563.00
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost	1.00	(5.00)	(11.00)
Actuarial loss reclassified to periodic cost	168.00	136.00	114.00
Transition obligation reclassified to periodic cost	2.00	4.00	3.00
Pension and non-pension postretirement benefit plans valuation adjustment	(371.00)	(250.00)	(288.00)
Change in unrealized gain (loss) on cash-flow hedges	(120.00)	88.00	(151.00)
Change in unrealized income (loss) on equity investments	1.00	0	0
Change in unrealized gain (loss) on marketable securities	2.00	0	(1.00)
Other comprehensive income (loss)	(317.00)	(27.00)	(334.00)
Comprehensive income	854.00	2,472.00	2,229.00
Average shares of common stock outstanding:
Basic	816.00	663.00	661.00
Diluted	819.00	665.00	663.00
Earnings per average common share - basic
Income from continuing operations	$ 1.42	$ 3.76	$ 3.88
Earnings per average common share - diluted
Net income	$ 1.42	$ 3.75	$ 3.87
Dividends per common share	$ 2.10	$ 2.10	$ 2.10
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating revenues	12,735.00	9,286.00	6,923.00
Operating revenues from affiliates	1,702.00	1,161.00	3,102.00
Total operating revenues	14,437.00	10,447.00	10,025.00
Operating expenses
Purchased power	7,061.00	3,589.00	3,463.00
Operating and maintenance	4,398.00	2,827.00	2,521.00
Operating and maintenance from affiliate	630.00	321.00	291.00
Depreciation and amortization	768.00	570.00	474.00
Taxes other than income	369.00	264.00	230.00
Total operating expenses	13,226.00	7,571.00	6,979.00
Gain (loss) on equity method investments	(91.00)	(1.00)
Operating income	1,120.00	2,875.00	3,046.00
Other income and deductions
Interest expense	(301.00)	(170.00)	(153.00)
Other, net	239.00	122.00	257.00
Total other income and deductions	(62.00)	(48.00)	104.00
Income before income taxes	1,058.00	2,827.00	3,150.00
Income taxes	500.00	1,056.00	1,178.00
Discontinued operations
Net income	558.00	1,771.00	1,972.00
Income (Loss) attributable to noncontrolling interest	4.00
Net income on membership interest	562.00	1,771.00	1,972.00
Pension and non-pension postretirement benefit plans:
Change in unrealized gain (loss) on cash-flow hedges	(403.00)	(98.00)	(144.00)
Change in unrealized income (loss) on equity investments	1.00
Other comprehensive income (loss)	(402.00)	(98.00)	(144.00)
Comprehensive income	156.00	1,673.00	1,828.00
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Operating revenues	5,441.00	6,054.00	6,202.00
Operating revenues from affiliates	2.00	2.00	2.00
Total operating revenues	5,443.00	6,056.00	6,204.00
Operating expenses
Purchased power	1,518.00	2,382.00	2,297.00
Purchased power from affiliate	789.00	653.00	1,010.00
Operating and maintenance	1,182.00	1,031.00	917.00
Operating and maintenance from affiliate	163.00	158.00	152.00
Depreciation and amortization	610.00	554.00	516.00
Taxes other than income	295.00	296.00	256.00
Total operating expenses	4,557.00	5,074.00	5,148.00
Operating income	886.00	982.00	1,056.00
Other income and deductions
Interest expense	(294.00)	(330.00)	(373.00)
Interest expense to affiliates, net	(13.00)	(15.00)	(13.00)
Other, net	39.00	29.00	24.00
Total other income and deductions	(268.00)	(316.00)	(362.00)
Income before income taxes	618.00	666.00	694.00
Income taxes	239.00	250.00	357.00
Discontinued operations
Net income	379.00	416.00	337.00
Pension and non-pension postretirement benefit plans:
Change in unrealized gain (loss) on marketable securities	1.00	0	(1.00)
Other comprehensive income (loss)	1.00	0	(1.00)
Comprehensive income	380.00	416.00	336.00
PECO Energy Co [Member]
Operating revenues [Abstract]
Operating revenues	3,183.00	3,715.00	5,514.00
Operating revenues from affiliates	3.00	5.00	5.00
Total operating revenues	3,186.00	3,720.00	5,519.00
Operating expenses
Purchased power	842.00	1,369.00	677.00
Purchased power from affiliate	533.00	495.00	2,085.00
Operating and maintenance	698.00	698.00	644.00
Operating and maintenance from affiliate	111.00	96.00	89.00
Depreciation and amortization	217.00	202.00	1,060.00
Taxes other than income	162.00	205.00	303.00
Total operating expenses	2,563.00	3,065.00	4,858.00
Operating income	623.00	655.00	661.00
Other income and deductions
Interest expense	(111.00)	(122.00)	(181.00)
Interest expense to affiliates, net	(12.00)	(12.00)	(12.00)
Other, net	8.00	14.00	8.00
Total other income and deductions	(115.00)	(120.00)	(185.00)
Income before income taxes	508.00	535.00	476.00
Income taxes	127.00	146.00	152.00
Discontinued operations
Net income	381.00	389.00	324.00
Preferred security dividends	(4.00)	(4.00)	(4.00)
Net income on common stock	377.00	385.00	320.00
Pension and non-pension postretirement benefit plans:
Amortization of realized loss on settled cash flow swaps	0	0	1.00
Change in unrealized gain (loss) on marketable securities	1.00	0	0
Other comprehensive income (loss)	1.00	0	(1.00)
Comprehensive income	382.00	389.00	323.00
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Operating revenues	2,725.00	3,060.00	3,534.00
Operating revenues from affiliates	10.00	8.00	7.00
Total operating revenues	2,735.00	3,068.00	3,541.00
Operating expenses
Purchased power and fuel	973.00	1,245.00	1,719.00
Purchased power from affiliate	396.00	348.00	428.00
Operating and maintenance	622.00	530.00	469.00
Operating and maintenance from affiliate	106.00	150.00	126.00
Depreciation and amortization	298.00	274.00	249.00
Taxes other than income	208.00	207.00	200.00
Total operating expenses	2,603.00	2,754.00	3,191.00
Operating income	132.00	314.00	350.00
Other income and deductions
Interest expense	(144.00)	(129.00)	(131.00)
Other, net	23.00	26.00	25.00
Total other income and deductions	(121.00)	(103.00)	(106.00)
Income before income taxes	11.00	211.00	244.00
Income taxes	7.00	75.00	97.00
Discontinued operations
Net income	4.00	136.00	147.00
Preferred security dividends	(13.00)	(13.00)	(13.00)
Net income on common stock	(9.00)	123.00	134.00
Pension and non-pension postretirement benefit plans:
Comprehensive income	$ 4.00	$ 136.00	$ 147.00