Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating revenues
Revenue from alternative revenue programs		$ 6	$ (155)	$ (69)
Total operating revenues		33,039	34,438	35,978
Operating expenses
Operating and maintenance		9,408	8,615	9,337
Depreciation and Amortization		5,014	4,252	4,353
Taxes other than income		1,714	1,732	1,783
Total operating expenses		30,240	30,096	32,143
Gain on sales of assets and businesses		24	31	56
Gain on deconsolidation of business		0	1	0
Operating income (loss)		2,823	4,374	3,891
Other income and (deductions)
Interest expense, net		(1,610)	(1,591)	(1,529)
Interest expense to affiliates		(25)	(25)	(25)
Other, net		1,145	1,227	(112)
Total other income and (deductions)		(490)	(389)	(1,666)
Income (loss) before income taxes		2,333	3,985	2,225
Income taxes		373	774	118
Equity in losses of unconsolidated affiliates		(6)	(183)	(28)
Net income (loss)		1,954	3,028	2,079
Net income (loss) attributable to common shareholders		1,963	2,936	2,005
Net income (loss) attributable to noncontrolling interests		(9)	92	74
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost		(40)	(65)	(66)
Actuarial loss reclassified to periodic cost		190	149	247
Pension and non-pension postretirement benefit plan valuation adjustment		(357)	(289)	(143)
Unrealized gain on cash flow hedges		(3)	0	12
Unrealized gain (loss) on investments in unconsolidated affiliates		0	1	2
Unrealized (loss) gain on foreign currency translation		4	6	(10)
Other comprehensive income (loss)		(206)	(198)	42
Comprehensive income (loss)		1,748	2,830	2,121
Comprehensive income attributable to noncontrolling interests		(9)	93	75
Comprehensive income (loss) attributable to common shareholders		$ 1,757	$ 2,737	$ 2,046
Average shares of common stock outstanding:
Weighted Average Number of Shares Outstanding, Basic		976	973	967
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements		1	1	2
Weighted Average Number of Shares Outstanding, Diluted	[1]	977	974	969
Earnings per average common share:
Earnings Per Share, Basic		$ 2.01	$ 3.02	$ 2.07
Earnings Per Share, Diluted		$ 2.01	$ 3.01	$ 2.07
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		0	0	3
Exelon Generation Co L L C [Member]
Operating revenues
Operating revenues from affiliates		$ 1,211	$ 1,172	$ 1,268
Total operating revenues		17,603	18,924	20,437
Operating expenses
Purchased power and/or fuel from affiliates		(7)	7	14
Operating and maintenance		4,613	4,131	4,803
Operating and maintenance from affiliates		555	587	661
Depreciation and Amortization		2,123	1,535	1,797
Taxes other than income		482	519	556
Total operating expenses		17,358	17,628	19,510
Gain on sales of assets and businesses		11	27	48
Operating income (loss)		256	1,323	975
Other income and (deductions)
Interest expense, net		(328)	(394)	(396)
Interest expense to affiliates		(29)	(35)	(36)
Other, net		937	1,023	(178)
Total other income and (deductions)		580	594	(610)
Income (loss) before income taxes		836	1,917	365
Income taxes		249	516	(108)
Equity in losses of unconsolidated affiliates		(8)	(184)	(30)
Net income (loss)		579	1,217	443
Net income (loss) attributable to noncontrolling interests		(10)	92	73
Net income (loss) attributable to membership interest		589	1,125	370
Other comprehensive income (loss), net of income taxes
Unrealized gain on cash flow hedges		(2)	0	12
Unrealized gain (loss) on investments in unconsolidated affiliates		0	1	1
Unrealized (loss) gain on foreign currency translation		4	6	(10)
Other comprehensive income (loss)		2	7	3
Comprehensive income (loss)		581	1,224	446
Comprehensive income attributable to noncontrolling interests		(10)	93	74
Comprehensive income (loss) attributable to common shareholders		591	1,131	372
Commonwealth Edison Co [Member]
Operating revenues
Revenue from alternative revenue programs		(47)	(133)	(29)
Operating revenues from affiliates		37	30	27
Total operating revenues		5,904	5,747	5,882
Operating expenses
Purchased power and/or fuel from affiliates		345	376	529
Operating and maintenance		1,231	1,041	1,068
Operating and maintenance from affiliates		289	264	267
Depreciation and Amortization		1,133	1,033	940
Taxes other than income		299	301	311
Total operating expenses		4,950	4,580	4,741
Gain on sales of assets and businesses		0	4	5
Operating income (loss)		954	1,171	1,146
Other income and (deductions)
Interest expense, net		(369)	(346)	(334)
Interest expense to affiliates		(13)	(13)	(13)
Other, net		43	39	33
Total other income and (deductions)		(339)	(320)	(314)
Income (loss) before income taxes		615	851	832
Income taxes		177	163	168
Net income (loss)		438	688	664
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)		438	688	664
PECO Energy Co [Member]
Operating revenues
Revenue from alternative revenue programs		16	(21)	(7)
Operating revenues from affiliates		9	6	8
Total operating revenues		3,058	3,100	3,038
Operating expenses
Purchased power and/or fuel from affiliates		188	157	126
Operating and maintenance		816	707	742
Operating and maintenance from affiliates		159	154	156
Depreciation and Amortization		347	333	301
Taxes other than income		172	165	163
Total operating expenses		2,512	2,388	2,452
Gain on sales of assets and businesses		0	1	1
Operating income (loss)		546	713	587
Other income and (deductions)
Interest expense, net		(136)	(124)	(115)
Interest expense to affiliates		(11)	(12)	(14)
Other, net		18	16	8
Total other income and (deductions)		(129)	(120)	(121)
Income (loss) before income taxes		417	593	466
Income taxes		(30)	65	6
Net income (loss)		447	528	460
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)		447	528	460
Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from alternative revenue programs		16	12	(26)
Operating revenues from affiliates		20	26	29
Total operating revenues		3,098	3,106	3,169
Operating expenses
Purchased power and/or fuel from affiliates		311	286	257
Operating and maintenance		617	600	615
Operating and maintenance from affiliates		172	160	162
Depreciation and Amortization		550	502	483
Taxes other than income		268	260	254
Total operating expenses		2,598	2,574	2,696
Gain on sales of assets and businesses		0	0	1
Operating income (loss)		500	532	474
Other income and (deductions)
Interest expense, net		(133)	(121)	(106)
Other, net		23	28	19
Total other income and (deductions)		(110)	(93)	(87)
Income (loss) before income taxes		390	439	387
Income taxes		41	79	74
Net income (loss)		349	360	313
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)		349	360	313
Pepco Holdings LLC [Member]
Operating revenues
Revenue from alternative revenue programs		21	(14)	(7)
Operating revenues from affiliates		17	14	15
Total operating revenues		4,663	4,806	4,798
Operating expenses
Purchased power and/or fuel from affiliates		366	352	355
Operating and maintenance		940	939	978
Operating and maintenance from affiliates		159	143	152
Depreciation and Amortization		782	754	740
Taxes other than income		450	450	455
Total operating expenses		4,045	4,084	4,156
Gain on sales of assets and businesses		11	0	1
Operating income (loss)		629	722	643
Other income and (deductions)
Interest expense, net		(268)	(263)	(261)
Other, net		57	55	43
Total other income and (deductions)		(211)	(208)	(218)
Income (loss) before income taxes		418	514	425
Income taxes		(77)	38	33
Equity in losses of unconsolidated affiliates		0	1	1
Net income (loss)		495	477	393
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss) attributable to common shareholders		495	477	393
Potomac Electric Power Company [Member]
Operating revenues
Revenue from alternative revenue programs		40	(3)	(7)
Operating revenues from affiliates		7	5	6
Total operating revenues		2,149	2,260	2,232
Operating expenses
Purchased power and/or fuel from affiliates		278	264	206
Operating and maintenance		248	273	275
Operating and maintenance from affiliates		205	209	226
Depreciation and Amortization		377	374	385
Taxes other than income		367	378	379
Total operating expenses		1,799	1,899	1,919
Gain on sales of assets and businesses		9	0	0
Operating income (loss)		359	361	313
Other income and (deductions)
Interest expense, net		(138)	(133)	(128)
Other, net		38	31	31
Total other income and (deductions)		(100)	(102)	(97)
Income (loss) before income taxes		259	259	216
Income taxes		(7)	16	11
Net income (loss)		266	243	205
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)		266	243	205
Delmarva Power & Light Company [Member]
Operating revenues
Revenue from alternative revenue programs		(7)	(11)	4
Operating revenues from affiliates		9	7	8
Total operating revenues		1,271	1,306	1,332
Operating expenses
Purchased power and/or fuel from affiliates		75	70	120
Operating and maintenance		208	171	182
Operating and maintenance from affiliates		153	152	162
Depreciation and Amortization		191	184	182
Taxes other than income		65	56	56
Total operating expenses		1,120	1,089	1,143
Gain on sales of assets and businesses		0	0	1
Operating income (loss)		151	217	190
Other income and (deductions)
Interest expense, net		(61)	(61)	(58)
Other, net		10	13	10
Total other income and (deductions)		(51)	(48)	(48)
Income (loss) before income taxes		100	169	142
Income taxes		(25)	22	22
Net income (loss)		125	147	120
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)		125	147	120
Atlantic City Electric Company [Member]
Operating revenues
Revenue from alternative revenue programs		(12)	0	(4)
Operating revenues from affiliates		4	3	3
Total operating revenues		1,245	1,240	1,236
Operating expenses
Purchased power and/or fuel from affiliates		13	19	29
Operating and maintenance		192	187	188
Operating and maintenance from affiliates		134	133	142
Depreciation and Amortization		180	157	136
Taxes other than income		8	4	5
Total operating expenses		1,123	1,089	1,087
Sale and Leaseback Transaction, Gain (Loss), Net		2	0	0
Operating income (loss)		124	151	149
Other income and (deductions)
Interest expense, net		(59)	(58)	(64)
Other, net		6	6	2
Total other income and (deductions)		(53)	(52)	(62)
Income (loss) before income taxes		71	99	87
Income taxes		(41)	0	12
Net income (loss)		112	99	75
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)		112	99	75
Generation commodities and services [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		16,400	17,754	19,168
Operating expenses
Purchased power and/or fuel		9,592	10,849	11,679
Generation commodities and services [Member] | Exelon Generation Co L L C [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		16,392	17,752	19,169
Operating expenses
Purchased power and/or fuel		9,592	10,849	11,679
Rate-regulated utility revenues [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		16,633	16,839	16,879
Operating expenses
Purchased power and/or fuel		4,512	4,648	4,991
Electricity, US Regulated [Member] | Commonwealth Edison Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		5,914	5,850	5,884
Operating expenses
Purchased power and/or fuel		1,653	1,565	1,626
Electricity, US Regulated [Member] | PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		2,519	2,505	2,469
Operating expenses
Purchased power and/or fuel		645	610	734
Electricity, US Regulated [Member] | Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		2,323	2,368	2,428
Operating expenses
Purchased power and/or fuel		509	585	671
Electricity, US Regulated [Member] | Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,463	4,639	4,609
Operating expenses
Purchased power and/or fuel		1,279	1,371	1,387
Electricity, US Regulated [Member] | Potomac Electric Power Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		2,102	2,258	2,233
Operating expenses
Purchased power and/or fuel		324	401	448
Electricity, US Regulated [Member] | Delmarva Power & Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,107	1,143	1,139
Operating expenses
Purchased power and/or fuel		359	381	352
Electricity, US Regulated [Member] | Atlantic City Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,253	1,237	1,237
Operating expenses
Purchased power and/or fuel		596	589	587
Natural Gas, US Regulated [Member] | PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		514	610	568
Operating expenses
Purchased power and/or fuel		185	262	230
Natural Gas, US Regulated [Member] | Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		739	700	738
Operating expenses
Purchased power and/or fuel		171	181	254
Natural Gas, US Regulated [Member] | Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		162	167	181
Operating expenses
Purchased power and/or fuel		69	75	89
Natural Gas, US Regulated [Member] | Delmarva Power & Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		162	167	181
Operating expenses
Purchased power and/or fuel		$ 69	$ 75	$ 89

[1] The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was less than 1 million for the years ended December 31, 2020 and December 31, 2019 and approximately 3 million for the year ended December 31, 2018.