Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating revenues
Competitive businesses revenues			$ 19,168	$ 17,394	$ 16,330
Rate-regulated utility revenues			16,879	15,964	14,988
Electric operating revenues				0	0
Natural gas operating revenues				0	0
Revenues from alternative revenue programs			(62)	207	48
Operating revenues from affiliates				0	0
Total operating revenues			35,985	33,565	31,366
Operating expenses
Competitive businesses purchased power and fuel			11,679	9,668	8,817
Rate-regulated utility purchased power and fuel			4,991	4,367	3,823
Operating and maintenance			9,337	10,025	9,954
Depreciation and amortization			4,353	3,828	3,936
Taxes other than income			1,783	1,731	1,576
Total operating expenses			32,143	29,619	28,106
Gain (loss) on sales of assets and businesses			56	3	(48)
Bargain purchase gain			0	233	0
Gain on deconsolidation of business			0	213	0
Operating income (loss)			3,898	4,395	3,212
Other income and (deductions)
Interest expense, net			(1,529)	(1,524)	(1,495)
Interest expense to affiliates			(25)	(36)	(41)
Other, net			(112)	947	297
Total other income and (deductions)			(1,666)	(613)	(1,239)
Income (loss) before income taxes			2,232	3,782	1,973
Income taxes			120	(126)	753
Equity in losses of unconsolidated affiliates			(28)	(32)	(24)
Net income (loss)			2,084	3,876	1,196
Net income (loss) attributable to noncontrolling interests and/or preference stock dividends			74	90	75
Net income (loss) attributable to common shareholders			2,010	3,786	1,121
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost			(66)	(56)	(48)
Actuarial loss reclassified to periodic cost			247	197	184
Pension and non-pension postretirement benefit plan valuation adjustment			(143)	10	(181)
Unrealized gain on cash flow hedges			12	3	2
Unrealized gain on marketable securities			0	6	1
Unrealized gain (loss) on investments in unconsolidated affiliates			2	4	(4)
Unrealized (loss) gain on foreign currency translation			(10)	7	10
Other comprehensive income (loss)			42	171	(36)
Comprehensive income (loss)			2,126	4,047	1,160
Comprehensive income attributable to noncontrolling interests and/or preference stock dividends			75	88	75
Comprehensive income (loss) attributable to common shareholders			$ 2,051	$ 3,959	$ 1,085
Average shares of common stock outstanding:
Weighted Average Number of Shares Outstanding, Basic			967	947	924
Weighted Average Number of Shares Outstanding, Diluted			969	949	927
Earnings per average common share:
Earnings Per Share, Basic			$ 2.08	$ 4.00	$ 1.21
Earnings Per Share, Diluted			$ 2.07	$ 3.99	$ 1.21
Exelon Generation Co L L C [Member]
Operating revenues
Competitive businesses revenues			$ 19,169	$ 17,385	$ 16,318
Rate-regulated utility revenues				0	0
Electric operating revenues				0	0
Natural gas operating revenues				0	0
Revenues from alternative revenue programs				0	0
Operating revenues from affiliates			1,268	1,115	1,439
Total operating revenues			20,437	18,500	17,757
Operating expenses
Competitive businesses purchased power and fuel			11,679	9,671	8,818
Purchased power and/or fuel from affiliates			14	19	12
Operating and maintenance			4,803	5,602	5,000
Operating and maintenance from affiliates			661	697	663
Depreciation and amortization			1,797	1,457	1,879
Taxes other than income			556	555	506
Total operating expenses			19,510	18,001	16,878
Gain (loss) on sales of assets and businesses			48	2	(59)
Bargain purchase gain			0	233	0
Gain on deconsolidation of business			0	213	0
Operating income (loss)			975	947	820
Other income and (deductions)
Interest expense, net			(396)	(401)	(325)
Interest expense to affiliates			(36)	(39)	(39)
Other, net			(178)	948	401
Total other income and (deductions)			(610)	508	37
Income (loss) before income taxes			365	1,455	857
Income taxes			(108)	(1,376)	282
Equity in losses of unconsolidated affiliates			(30)	(33)	(25)
Net income (loss)			443	2,798	550
Net income (loss) attributable to noncontrolling interests			73	88	67
Net income (loss) attributable to membership interest			370	2,710	483
Other comprehensive income (loss), net of income taxes
Unrealized gain on cash flow hedges			12	3	2
Unrealized gain on marketable securities			0	1	1
Unrealized gain (loss) on investments in unconsolidated affiliates			1	4	(4)
Unrealized (loss) gain on foreign currency translation			(10)	7	10
Other comprehensive income (loss)			3	15	9
Comprehensive income (loss)			446	2,813	559
Comprehensive income attributable to noncontrolling interests and/or preference stock dividends			74	86	67
Comprehensive income (loss) attributable to common shareholders			372	2,727	492
Commonwealth Edison Co [Member]
Operating revenues
Competitive businesses revenues				0	0
Rate-regulated utility revenues				0	0
Electric operating revenues			5,884	5,478	5,263
Natural gas operating revenues				0	0
Revenues from alternative revenue programs			(29)	43	(24)
Operating revenues from affiliates			27	15	15
Total operating revenues			5,882	5,536	5,254
Operating expenses
Purchased power			1,626	1,533	1,411
Purchased power and/or fuel from affiliates			529	108	47
Operating and maintenance			1,068	1,157	1,303
Operating and maintenance from affiliates			267	270	227
Depreciation and amortization			940	850	775
Taxes other than income			311	296	293
Total operating expenses			4,741	4,214	4,056
Gain (loss) on sales of assets and businesses			5	1	7
Operating income (loss)			1,146	1,323	1,205
Other income and (deductions)
Interest expense, net			(334)	(348)	(448)
Interest expense to affiliates			(13)	(13)	(13)
Other, net			33	22	(65)
Total other income and (deductions)			(314)	(339)	(526)
Income (loss) before income taxes			832	984	679
Income taxes			168	417	301
Net income (loss)			664	567	378
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)			664	567	378
PECO Energy Co [Member]
Operating revenues
Competitive businesses revenues				0	0
Rate-regulated utility revenues				0	0
Electric operating revenues			2,469	2,369	2,524
Natural gas operating revenues			568	494	462
Revenues from alternative revenue programs			(7)	0	0
Operating revenues from affiliates			8	7	8
Total operating revenues			3,038	2,870	2,994
Operating expenses
Purchased power			734	648	598
Purchased fuel			230	186	162
Purchased power and/or fuel from affiliates			126	135	287
Operating and maintenance			742	657	665
Operating and maintenance from affiliates			156	149	146
Depreciation and amortization			301	286	270
Taxes other than income			163	154	164
Total operating expenses			2,452	2,215	2,292
Gain (loss) on sales of assets and businesses			1	0	0
Operating income (loss)			587	655	702
Other income and (deductions)
Interest expense, net			(115)	(115)	(111)
Interest expense to affiliates			(14)	(11)	(12)
Other, net			8	9	8
Total other income and (deductions)			(121)	(117)	(115)
Income (loss) before income taxes			466	538	587
Income taxes			6	104	149
Net income (loss)			460	434	438
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)			460	434	438
Baltimore Gas and Electric Company [Member]
Operating revenues
Competitive businesses revenues				0	0
Rate-regulated utility revenues				0	0
Electric operating revenues			2,428	2,384	2,531
Natural gas operating revenues			738	652	628
Revenues from alternative revenue programs			(26)	124	53
Operating revenues from affiliates			29	16	21
Total operating revenues			3,169	3,176	3,233
Operating expenses
Purchased power			671	566	528
Purchased fuel			254	183	162
Purchased power and/or fuel from affiliates			257	384	604
Operating and maintenance			615	563	605
Operating and maintenance from affiliates			162	153	132
Depreciation and amortization			483	473	423
Taxes other than income			254	240	229
Total operating expenses			2,696	2,562	2,683
Gain (loss) on sales of assets and businesses			1	0	0
Operating income (loss)			474	614	550
Other income and (deductions)
Interest expense, net			(106)	(95)	(87)
Interest expense to affiliates			0	(10)	(16)
Other, net			19	16	21
Total other income and (deductions)			(87)	(89)	(82)
Income (loss) before income taxes			387	525	468
Income taxes			74	218	174
Net income (loss)			313	307	294
Preference stock dividends			0	0	8
Net income (loss) attributable to common shareholders			313	307	286
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)			313	307	294
Comprehensive income attributable to noncontrolling interests and/or preference stock dividends			0	0	8
Comprehensive income (loss) attributable to common shareholders			313	307	286
Pepco Holdings LLC [Member]
Operating revenues
Electric operating revenues			4,609	4,428
Natural gas operating revenues			181	161
Revenues from alternative revenue programs			0	40
Operating revenues from affiliates			15	50
Total operating revenues			4,805	4,679
Operating expenses
Purchased power			1,387	1,182
Purchased fuel			89	71
Purchased power and/or fuel from affiliates			355	463
Operating and maintenance			978	918
Operating and maintenance from affiliates			152	150
Depreciation and amortization			740	675
Taxes other than income			455	452
Total operating expenses			4,156	3,911
Gain (loss) on sales of assets and businesses			1	1
Operating income (loss)			650	769
Other income and (deductions)
Interest expense, net			(261)	(245)
Other, net			43	54
Total other income and (deductions)			(218)	(191)
Income (loss) before income taxes			432	578
Income taxes			35	217
Equity in losses of unconsolidated affiliates			1	1
Net income (loss)			398	362
Net income (loss) attributable to membership interest			398	362
Other comprehensive income (loss), net of income taxes
Actuarial loss reclassified to periodic cost			0	0
Other comprehensive income (loss)			0	0
Comprehensive income (loss) attributable to common shareholders			398	362
Pepco Holdings LLC [Member] | Predecessor [Member]
Operating revenues
Competitive businesses revenues	$ 0
Rate-regulated utility revenues	0
Electric operating revenues	1,122
Natural gas operating revenues	57
Revenues from alternative revenue programs	(26)
Operating revenues from affiliates	0
Total operating revenues	1,153
Operating expenses
Purchased power	471
Purchased fuel	26
Purchased power and/or fuel from affiliates	0
Operating and maintenance	294
Operating and maintenance from affiliates	0
Depreciation and amortization	152
Taxes other than income	105
Total operating expenses	1,048
Gain (loss) on sales of assets and businesses	0
Operating income (loss)	105
Other income and (deductions)
Interest expense, net	(65)
Other, net	(4)
Total other income and (deductions)	(69)
Income (loss) before income taxes	36
Income taxes	17
Equity in losses of unconsolidated affiliates	0
Net income (loss)	19
Net income (loss) attributable to membership interest	19
Other comprehensive income (loss), net of income taxes
Actuarial loss reclassified to periodic cost	1
Other comprehensive income (loss)	1
Comprehensive income (loss) attributable to common shareholders	$ 20
Pepco Holdings LLC [Member] | Successor [Member]
Operating revenues
Competitive businesses revenues		$ 0		0
Rate-regulated utility revenues		0		0
Electric operating revenues		3,463		4,428
Natural gas operating revenues		92		161
Revenues from alternative revenue programs		43		40
Operating revenues from affiliates		45	15	50
Total operating revenues		3,643		4,679
Operating expenses
Purchased power		925
Purchased fuel		36
Purchased power and/or fuel from affiliates		486
Operating and maintenance		1,144
Operating and maintenance from affiliates		89	152	150
Depreciation and amortization		515
Taxes other than income		354
Total operating expenses		3,549
Gain (loss) on sales of assets and businesses		(1)
Operating income (loss)		93
Other income and (deductions)
Interest expense, net		(195)
Other, net		44
Total other income and (deductions)		(151)
Income (loss) before income taxes		(58)
Income taxes		3
Equity in losses of unconsolidated affiliates		0
Net income (loss)		(61)
Net income (loss) attributable to membership interest		(61)
Other comprehensive income (loss), net of income taxes
Actuarial loss reclassified to periodic cost		0
Other comprehensive income (loss)		0
Comprehensive income (loss) attributable to common shareholders		$ (61)
Potomac Electric Power Company [Member]
Operating revenues
Competitive businesses revenues				0	0
Rate-regulated utility revenues				0	0
Electric operating revenues			2,233	2,126	2,167
Natural gas operating revenues				0	0
Revenues from alternative revenue programs			0	26	14
Operating revenues from affiliates			6	6	5
Total operating revenues			2,239	2,158	2,186
Operating expenses
Purchased power			448	359	411
Purchased power and/or fuel from affiliates			206	255	295
Operating and maintenance			275	396	607
Operating and maintenance from affiliates			226	58	35
Depreciation and amortization			385	321	295
Taxes other than income			379	371	377
Total operating expenses			1,919	1,760	2,020
Gain (loss) on sales of assets and businesses			0	1	8
Operating income (loss)			320	399	174
Other income and (deductions)
Interest expense, net			(128)	(121)	(127)
Other, net			31	32	36
Total other income and (deductions)			(97)	(89)	(91)
Income (loss) before income taxes			223	310	83
Income taxes			13	105	41
Net income (loss)			210	205	42
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)			210	205	42
Delmarva Power & Light Company [Member]
Operating revenues
Competitive businesses revenues				0	0
Rate-regulated utility revenues				0	0
Electric operating revenues			1,139	1,125	1,128
Natural gas operating revenues			181	161	148
Revenues from alternative revenue programs			4	6	(6)
Operating revenues from affiliates			8	8	7
Total operating revenues			1,332	1,300	1,277
Operating expenses
Purchased power			352	282	369
Purchased fuel			89	71	60
Purchased power and/or fuel from affiliates			120	179	154
Operating and maintenance			182	283	422
Operating and maintenance from affiliates			162	32	19
Depreciation and amortization			182	167	157
Taxes other than income			56	57	55
Total operating expenses			1,143	1,071	1,236
Gain (loss) on sales of assets and businesses			1	0	9
Operating income (loss)			190	229	50
Other income and (deductions)
Interest expense, net			(58)	(51)	(50)
Other, net			10	14	13
Total other income and (deductions)			(48)	(37)	(37)
Income (loss) before income taxes			142	192	13
Income taxes			22	71	22
Net income (loss)			120	121	(9)
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)			120	121	(9)
Atlantic City Electric Company [Member]
Operating revenues
Competitive businesses revenues				0	0
Rate-regulated utility revenues				0	0
Electric operating revenues			1,237	1,176	1,245
Natural gas operating revenues				0	0
Revenues from alternative revenue programs			(4)	8	9
Operating revenues from affiliates			3	2	3
Total operating revenues			1,236	1,186	1,257
Operating expenses
Purchased power			587	541	614
Purchased power and/or fuel from affiliates			29	29	37
Operating and maintenance			188	279	410
Operating and maintenance from affiliates			142	28	18
Depreciation and amortization			136	146	165
Taxes other than income			5	6	7
Total operating expenses			1,087	1,029	1,251
Gain (loss) on sales of assets and businesses			0	0	1
Operating income (loss)			149	157	7
Other income and (deductions)
Interest expense, net			(64)	(61)	(62)
Other, net			2	7	9
Total other income and (deductions)			(62)	(54)	(53)
Income (loss) before income taxes			87	103	(46)
Income taxes			12	26	(4)
Net income (loss)			75	77	(42)
Other comprehensive income (loss), net of income taxes
Comprehensive income (loss)			$ 75	$ 77	$ (42)