Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating revenues
Revenue from alternative revenue programs	$ (155)	$ (69)	$ 200
Total operating revenues	34,438	35,978	33,558
Operating expenses
Operating and maintenance	8,615	9,337	10,025
Depreciation and Amortization	4,252	4,353	3,828
Taxes other than income	1,732	1,783	1,731
Total operating expenses	30,096	32,143	29,619
Gain on sales of assets and businesses	31	56	3
Bargain purchase gain	0	0	233
Gain on deconsolidation of business	1	0	213
Operating income (loss)	4,374	3,891	4,388
Other income and (deductions)
Interest expense, net	(1,591)	(1,529)	(1,524)
Interest expense to affiliates	(25)	(25)	(36)
Other, net	1,227	(112)	947
Total other income and (deductions)	(389)	(1,666)	(613)
Income (loss) before income taxes	3,985	2,225	3,775
Income taxes	774	118	(126)
Equity in losses of unconsolidated affiliates	(183)	(28)	(32)
Net income (loss)	3,028	2,079	3,869
Net income (loss) attributable to noncontrolling interests and/or preference stock dividends	92	74	90
Net income (loss) attributable to common shareholders	2,936	2,005	3,779
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost	(65)	(66)	(56)
Actuarial loss reclassified to periodic cost	149	247	197
Pension and non-pension postretirement benefit plan valuation adjustment	(289)	(143)	10
Unrealized gain on cash flow hedges	0	12	3
Unrealized gain on marketable securities	0	0	6
Unrealized gain (loss) on investments in unconsolidated affiliates	1	2	4
Unrealized (loss) gain on foreign currency translation	6	(10)	7
Other comprehensive income (loss)	(198)	42	171
Comprehensive income (loss)	2,830	2,121	4,040
Comprehensive income attributable to noncontrolling interests and/or preference stock dividends	93	75	88
Comprehensive income (loss) attributable to common shareholders	$ 2,737	$ 2,046	$ 3,952
Average shares of common stock outstanding:
Weighted Average Number of Shares Outstanding, Basic	973	967	947
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	1	2	2
Weighted Average Number of Shares Outstanding, Diluted	974	969	949
Earnings per average common share:
Earnings Per Share, Basic	$ 3.02	$ 2.07	$ 3.99
Earnings Per Share, Diluted	$ 3.01	$ 2.07	$ 3.98
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		3	8
Exelon Generation Co L L C [Member]
Operating revenues
Operating revenues from affiliates	$ 1,172	$ 1,268	$ 1,115
Total operating revenues	18,924	20,437	18,500
Operating expenses
Purchased power and/or fuel from affiliates	7	14	19
Operating and maintenance	4,131	4,803	5,602
Operating and maintenance from affiliates	587	661	697
Depreciation and Amortization	1,535	1,797	1,457
Taxes other than income	519	556	555
Total operating expenses	17,628	19,510	18,001
Gain on sales of assets and businesses	27	48	2
Bargain purchase gain	0	0	233
Gain on deconsolidation of business	0	0	213
Operating income (loss)	1,323	975	947
Other income and (deductions)
Interest expense, net	(394)	(396)	(401)
Interest expense to affiliates	(35)	(36)	(39)
Other, net	1,023	(178)	948
Total other income and (deductions)	594	(610)	508
Income (loss) before income taxes	1,917	365	1,455
Income taxes	516	(108)	(1,376)
Equity in losses of unconsolidated affiliates	(184)	(30)	(33)
Net income (loss)	1,217	443	2,798
Net income (loss) attributable to noncontrolling interests	92	73	88
Net income (loss) attributable to membership interest	1,125	370	2,710
Other comprehensive income (loss), net of income taxes
Unrealized gain on cash flow hedges	0	12	3
Unrealized gain on marketable securities	0	0	1
Unrealized gain (loss) on investments in unconsolidated affiliates	1	1	4
Unrealized (loss) gain on foreign currency translation	6	(10)	7
Other comprehensive income (loss)	7	3	15
Comprehensive income (loss)	1,224	446	2,813
Comprehensive income attributable to noncontrolling interests and/or preference stock dividends	93	74	86
Comprehensive income (loss) attributable to common shareholders	1,131	372	2,727
Commonwealth Edison Co [Member]
Operating revenues
Revenue from alternative revenue programs	(133)	(29)	43
Operating revenues from affiliates	30	27	15
Total operating revenues	5,747	5,882	5,536
Operating expenses
Purchased power and/or fuel from affiliates	376	529	108
Operating and maintenance	1,041	1,068	1,157
Operating and maintenance from affiliates	264	267	270
Depreciation and Amortization	1,033	940	850
Taxes other than income	301	311	296
Total operating expenses	4,580	4,741	4,214
Gain on sales of assets and businesses	4	5	1
Operating income (loss)	1,171	1,146	1,323
Other income and (deductions)
Interest expense, net	(346)	(334)	(348)
Interest expense to affiliates	(13)	(13)	(13)
Other, net	39	33	22
Total other income and (deductions)	(320)	(314)	(339)
Income (loss) before income taxes	851	832	984
Income taxes	163	168	417
Net income (loss)	688	664	567
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)	688	664	567
PECO Energy Co [Member]
Operating revenues
Revenue from alternative revenue programs	(21)	(7)	0
Operating revenues from affiliates	6	8	7
Total operating revenues	3,100	3,038	2,870
Operating expenses
Purchased power and/or fuel from affiliates	157	126	135
Operating and maintenance	707	742	657
Operating and maintenance from affiliates	154	156	149
Depreciation and Amortization	333	301	286
Taxes other than income	165	163	154
Total operating expenses	2,388	2,452	2,215
Gain on sales of assets and businesses	1	1	0
Operating income (loss)	713	587	655
Other income and (deductions)
Interest expense, net	(124)	(115)	(115)
Interest expense to affiliates	(12)	(14)	(11)
Other, net	16	8	9
Total other income and (deductions)	(120)	(121)	(117)
Income (loss) before income taxes	593	466	538
Income taxes	65	6	104
Net income (loss)	528	460	434
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)	528	460	434
Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from alternative revenue programs	12	(26)	124
Operating revenues from affiliates	26	29	16
Total operating revenues	3,106	3,169	3,176
Operating expenses
Purchased power and/or fuel from affiliates	286	257	384
Operating and maintenance	600	615	563
Operating and maintenance from affiliates	160	162	153
Depreciation and Amortization	502	483	473
Taxes other than income	260	254	240
Total operating expenses	2,574	2,696	2,562
Gain on sales of assets and businesses	0	1	0
Operating income (loss)	532	474	614
Other income and (deductions)
Interest expense, net	(121)	(106)	(95)
Interest expense to affiliates	0	0	(10)
Other, net	28	19	16
Total other income and (deductions)	(93)	(87)	(89)
Income (loss) before income taxes	439	387	525
Income taxes	79	74	218
Net income (loss)	360	313	307
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)	360	313	307
Pepco Holdings LLC [Member]
Operating revenues
Revenue from alternative revenue programs	(14)	(7)	33
Operating revenues from affiliates	14	15	50
Total operating revenues	4,806	4,798	4,672
Operating expenses
Purchased power and/or fuel from affiliates	352	355	463
Operating and maintenance	939	978	918
Operating and maintenance from affiliates	143	152	150
Depreciation and Amortization	754	740	675
Taxes other than income	450	455	452
Total operating expenses	4,084	4,156	3,911
Gain on sales of assets and businesses	0	1	1
Operating income (loss)	722	643	762
Other income and (deductions)
Interest expense, net	(263)	(261)	(245)
Other, net	55	43	54
Total other income and (deductions)	(208)	(218)	(191)
Income (loss) before income taxes	514	425	571
Income taxes	38	33	217
Equity in losses of unconsolidated affiliates	1	1	1
Net income (loss)	477	393	355
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss) attributable to common shareholders	477	393	355
Potomac Electric Power Company [Member]
Operating revenues
Revenue from alternative revenue programs	(3)	(7)	19
Operating revenues from affiliates	5	6	6
Total operating revenues	2,260	2,232	2,151
Operating expenses
Purchased power and/or fuel from affiliates	264	206	255
Operating and maintenance	273	275	396
Operating and maintenance from affiliates	209	226	58
Depreciation and Amortization	374	385	321
Taxes other than income	378	379	371
Total operating expenses	1,899	1,919	1,760
Gain on sales of assets and businesses	0	0	1
Operating income (loss)	361	313	392
Other income and (deductions)
Interest expense, net	(133)	(128)	(121)
Other, net	31	31	32
Total other income and (deductions)	(102)	(97)	(89)
Income (loss) before income taxes	259	216	303
Income taxes	16	11	105
Net income (loss)	243	205	198
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)	243	205	198
Delmarva Power & Light Company [Member]
Operating revenues
Revenue from alternative revenue programs	(11)	4	6
Operating revenues from affiliates	7	8	8
Total operating revenues	1,306	1,332	1,300
Operating expenses
Purchased power and/or fuel from affiliates	70	120	179
Operating and maintenance	171	182	283
Operating and maintenance from affiliates	152	162	32
Depreciation and Amortization	184	182	167
Taxes other than income	56	56	57
Total operating expenses	1,089	1,143	1,071
Gain on sales of assets and businesses	0	1	0
Operating income (loss)	217	190	229
Other income and (deductions)
Interest expense, net	(61)	(58)	(51)
Other, net	13	10	14
Total other income and (deductions)	(48)	(48)	(37)
Income (loss) before income taxes	169	142	192
Income taxes	22	22	71
Net income (loss)	147	120	121
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)	147	120	121
Atlantic City Electric Company [Member]
Operating revenues
Revenue from alternative revenue programs	0	(4)	8
Operating revenues from affiliates	3	3	2
Total operating revenues	1,240	1,236	1,186
Operating expenses
Purchased power and/or fuel from affiliates	19	29	29
Operating and maintenance	187	188	279
Operating and maintenance from affiliates	133	142	28
Depreciation and Amortization	157	136	146
Taxes other than income	4	5	6
Total operating expenses	1,089	1,087	1,029
Operating income (loss)	151	149	157
Other income and (deductions)
Interest expense, net	(58)	(64)	(61)
Other, net	6	2	7
Total other income and (deductions)	(52)	(62)	(54)
Income (loss) before income taxes	99	87	103
Income taxes	0	12	26
Net income (loss)	99	75	77
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)	99	75	77
Generation commodities and services [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	17,754	19,168	17,394
Operating expenses
Purchased power and/or fuel	10,849	11,679	9,668
Generation commodities and services [Member] | Exelon Generation Co L L C [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	17,752	19,169	17,385
Operating expenses
Purchased power and/or fuel	10,849	11,679	9,671
Rate-regulated utility revenues [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	16,839	16,879	15,964
Operating expenses
Purchased power and/or fuel	4,648	4,991	4,367
Electricity, US Regulated [Member] | Commonwealth Edison Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	5,850	5,884	5,478
Operating expenses
Purchased power and/or fuel	1,565	1,626	1,533
Electricity, US Regulated [Member] | PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	2,505	2,469	2,369
Operating expenses
Purchased power and/or fuel	610	734	648
Electricity, US Regulated [Member] | Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	2,368	2,428	2,384
Operating expenses
Purchased power and/or fuel	585	671	566
Electricity, US Regulated [Member] | Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	4,639	4,609	4,428
Operating expenses
Purchased power and/or fuel	1,371	1,387	1,182
Electricity, US Regulated [Member] | Potomac Electric Power Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	2,258	2,233	2,126
Operating expenses
Purchased power and/or fuel	401	448	359
Electricity, US Regulated [Member] | Delmarva Power & Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	1,143	1,139	1,125
Operating expenses
Purchased power and/or fuel	381	352	282
Electricity, US Regulated [Member] | Atlantic City Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	1,237	1,237	1,176
Operating expenses
Purchased power and/or fuel	589	587	541
Natural Gas, US Regulated [Member] | PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	610	568	494
Operating expenses
Purchased power and/or fuel	262	230	186
Natural Gas, US Regulated [Member] | Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	700	738	652
Operating expenses
Purchased power and/or fuel	181	254	183
Natural Gas, US Regulated [Member] | Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	167	181	161
Operating expenses
Purchased power and/or fuel	75	89	71
Natural Gas, US Regulated [Member] | Delmarva Power & Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax	167	181	161
Operating expenses
Purchased power and/or fuel	$ 75	$ 89	$ 71