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, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating revenues
Operating Revenue				$ 17,360	$ 16,324	$ 18,395
Regulated Operating Revenue				16,171	15,036	11,052
Electric operating revenues	[1]			14,840	13,869	9,876
Natural gas operating revenues	[1]			1,333	1,166	1,176
Operating revenues from affiliates				7	10	9
Total operating revenues				33,531	31,360	29,447
Operating expenses
Competitive businesses purchased power and fuel				9,668	8,817	10,007
Cost of Purchased Power				4,367	3,823	3,077
Operating and maintenance				10,126	10,048	8,322
Depreciation and amortization				3,828	3,936	2,450
Taxes other than income				1,731	1,576	1,200
Total operating expenses				29,720	28,200	25,056
Gain (Loss) on Disposition of Other Assets				3	(48)	18
Bargain purchase gain				233	0	0
Gain on deconsolidation of business				213	0	0
Operating Income (Loss)				4,260	3,112	4,409
Other income and (deductions)
Interest Expense				(1,524)	(1,495)	(992)
Interest expense to affiliates				(36)	(41)	(41)
Other, net				1,056	413	(46)
Total other income and (deductions)				(504)	(1,123)	(1,079)
Income before income taxes				3,756	1,989	3,330
Income before income taxes				3,756	1,989	3,330
Income taxes				(125)	761	1,073
Income (Loss) from Equity Method Investments				(32)	(24)	(7)
Net Income (Loss)				3,849	1,204	2,250
Net Income Loss Attributable To Noncontrolling Interest And Preferred Stock Dividends And Other Adjustments				79	70	(19)
Net income attributable to common shareholders				3,770	1,134	2,269
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost, net of tax				(56)	(48)	(46)
Actuarial loss reclassified to periodic cost, net of tax				197	184	220
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax				(10)	181	99
Unrealized gain (loss) on cash flow hedges, net of taxes			$ 0	(3)	(2)	(9)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax				6	1	0
Unrealized gain (loss) on foreign currency translation, net of taxes				7	10	(21)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax				4	(4)	(3)
Other comprehensive income (loss)				171	(36)	60
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest				4,020	1,168	2,310
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest				77	70	(19)
Comprehensive income				$ 3,943	$ 1,098	$ 2,329
Average shares of common stock outstanding:
Basic				947	924	890
Diluted				949	927	893
Earnings per average common share:
Earnings Per Share, Basic				$ 3.98	$ 1.23	$ 2.55
Diluted (in usd per share)				3.97	1.22	2.54
Dividends per common share (in usd per share)				$ 1.31	$ 1.26	$ 1.24
Predecessor [Member]
Other income and (deductions)
Income (Loss) from Equity Method Investments						$ 0
Exelon Generation Co L L C [Member]
Operating revenues
Operating Revenue				$ 17,351	$ 16,312	18,386
Operating revenues from affiliates				1,115	1,439	749
Total operating revenues				18,466	17,751	19,135
Operating expenses
Cost of Purchased Power				9,671	8,818	10,007
Purchased power from affiliate				19	12	14
Operating and maintenance				5,594	4,978	4,688
Operating and maintenance from affiliates				697	663	620
Depreciation and amortization				1,457	1,879	1,054
Taxes other than income				555	506	489
Total operating expenses				17,993	16,856	16,872
Gain (Loss) on Disposition of Other Assets				2	(59)	12
Bargain purchase gain				233	0	0
Gain on deconsolidation of business				213	0	0
Operating Income (Loss)				921	836	2,275
Other income and (deductions)
Interest Expense				(401)	(325)	(322)
Interest expense to affiliates				(39)	(39)	(43)
Other, net				948	401	(60)
Total other income and (deductions)				508	37	(425)
Income before income taxes				1,429	873	1,850
Income taxes				(1,375)	290	502
Income (Loss) from Equity Method Investments						(8)
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions				(33)	(25)	(8)
Net Income (Loss)				2,771	558	1,340
Income (Loss) Attributable to Noncontrolling Interest, before Tax				77	62	(32)
Net income attributable to membership interest				2,694	496	1,372
Pension and non-pension postretirement benefit plans:
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions				(33)	(25)	(8)
Unrealized gain (loss) on cash flow hedges, net of taxes				(3)	(2)	3
Other Comprehensive Income Unrealized Income Loss On Equity Investments Arising During Period Net Of Tax				4	(4)	(3)
Unrealized gain (loss) on foreign currency translation, net of taxes				7	10	(21)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax				1	1	0
Other comprehensive income (loss)				15	9	(27)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest				2,786	567	1,313
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest				75	62	(32)
Comprehensive income				2,711	505	1,345
Commonwealth Edison Co [Member]
Operating revenues
Electric operating revenues				5,521	5,239	4,901
Operating revenues from affiliates				15	15	4
Total operating revenues				5,536	5,254	4,905
Operating expenses
Purchased power				1,533	1,411	1,301
Purchased power from affiliate				108	47	18
Operating and maintenance				1,157	1,303	1,372
Operating and maintenance from affiliates				270	227	195
Depreciation and amortization				850	775	707
Taxes other than income				296	293	296
Total operating expenses				4,214	4,056	3,889
Gain (Loss) on Disposition of Other Assets				1	7	1
Operating Income (Loss)				1,323	1,205	1,017
Other income and (deductions)
Interest Expense				(348)	(448)	(319)
Interest expense to affiliates				(13)	(13)	(13)
Other, net				22	(65)	21
Total other income and (deductions)				(339)	(526)	(311)
Income before income taxes				984	679	706
Income taxes				417	301	280
Income (Loss) from Equity Method Investments				0	0	0
Net Income (Loss)				567	378	426
Pension and non-pension postretirement benefit plans:
Comprehensive income				567	378	426
PECO Energy Co [Member]
Operating revenues
Electric operating revenues				2,369	2,524	2,485
Natural gas operating revenues				494	462	545
Operating revenues from affiliates				7	8	2
Total operating revenues				2,870	2,994	3,032
Operating expenses
Purchased power				648	598	735
Purchased fuel				186	162	235
Purchased power from affiliate				135	287	220
Operating and maintenance				657	665	684
Operating and maintenance from affiliates				149	146	110
Depreciation and amortization				286	270	260
Taxes other than income				154	164	160
Total operating expenses				2,215	2,292	2,404
Gain (Loss) on Disposition of Other Assets				0	0	2
Operating Income (Loss)				655	702	630
Other income and (deductions)
Interest Expense				(115)	(111)	(102)
Interest expense to affiliates				(11)	(12)	(12)
Other, net				9	8	5
Total other income and (deductions)				(117)	(115)	(109)
Income before income taxes				538	587	521
Income taxes				104	149	143
Income (Loss) from Equity Method Investments				0	0	0
Net Income (Loss)				434	438	378
Net income attributable to common shareholders				434	438	378
Pension and non-pension postretirement benefit plans:
Comprehensive income				434	438	378
Baltimore Gas and Electric Company [Member]
Operating revenues
Electric operating revenues				2,484	2,603	2,490
Natural gas operating revenues				676	609	631
Operating revenues from affiliates				16	21	14
Total operating revenues				3,176	3,233	3,135
Operating expenses
Purchased power				566	528	602
Purchased fuel				183	162	205
Purchased power from affiliate				384	604	498
Operating and maintenance				563	605	565
Operating and maintenance from affiliates				153	132	118
Depreciation and amortization				473	423	366
Taxes other than income				240	229	224
Total operating expenses				2,562	2,683	2,578
Gain (Loss) on Disposition of Other Assets				0	0	1
Operating Income (Loss)				614	550	558
Other income and (deductions)
Interest Expense				(95)	(87)	(83)
Interest expense to affiliates				(10)	(16)	(16)
Other, net				16	21	18
Total other income and (deductions)				(89)	(82)	(81)
Income before income taxes				525	468	477
Income taxes				218	174	189
Income (Loss) from Equity Method Investments				0	0	0
Net Income (Loss)				307	294	288
Dividends, Preferred Stock				0	8	13
Net income attributable to common shareholders				307	286	275
Pension and non-pension postretirement benefit plans:
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest				307	294	288
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest				0	8	13
Comprehensive income				307	286	275
Pepco Holdings LLC [Member]
Operating expenses
Purchased power from affiliate		$ 0				0
Pepco Holdings LLC [Member] | Predecessor [Member]
Operating revenues
Electric operating revenues		1,096				4,770
Natural gas operating revenues		57				165
Operating revenues from affiliates		0				0
Total operating revenues		1,153				4,935
Operating expenses
Purchased power		471				1,986
Purchased fuel		26				87
Operating and maintenance		294				1,156
Operating and maintenance from affiliates		0				0
Depreciation and amortization		152				624
Taxes other than income		105				455
Total operating expenses		1,048				4,308
Gain (Loss) on Disposition of Other Assets		0				46
Operating Income (Loss)		105				673
Other income and (deductions)
Interest Expense		(65)				(280)
Other, net		(4)				88
Total other income and (deductions)		(69)				(192)
Income before income taxes		36				481
Income taxes		17				163
Income (Loss) from Equity Method Investments		0
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions		0				0
Net Income (Loss)		19				327
Net income attributable to membership interest		19				327
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest		19				318
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest		0				9
Pension and non-pension postretirement benefit plans:
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions		0				0
Actuarial loss reclassified to periodic cost, net of tax		1				9
Unrealized gain (loss) on cash flow hedges, net of taxes		0				(1)
Other comprehensive income (loss)		1				10
Comprehensive income		$ 20				337
Pepco Holdings LLC [Member] | Successor [Member]
Operating revenues
Electric operating revenues			3,506	4,468
Natural gas operating revenues			92	161
Operating revenues from affiliates			45	50
Total operating revenues			3,643	4,679
Operating expenses
Purchased power			925	1,182
Purchased fuel			36	71
Purchased power from affiliate			486	463
Operating and maintenance			1,144	918
Operating and maintenance from affiliates			89	150
Depreciation and amortization			515	675
Taxes other than income			354	452
Total operating expenses			3,549	3,911
Gain (Loss) on Disposition of Other Assets			(1)	1
Operating Income (Loss)			93	769
Other income and (deductions)
Interest Expense			(195)	(245)
Other, net			44	54
Total other income and (deductions)			(151)	(191)
Income before income taxes			(58)	578
Income taxes			3	217
Income (Loss) from Equity Method Investments			0	(1)
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions			0	1
Net Income (Loss)			(61)	362
Net income attributable to membership interest			(61)	362
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest			(61)	362
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest			0	0
Pension and non-pension postretirement benefit plans:
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions			0	1
Actuarial loss reclassified to periodic cost, net of tax			0	0
Unrealized gain (loss) on cash flow hedges, net of taxes				0
Other comprehensive income (loss)			0	0
Comprehensive income			$ (61)	362
Potomac Electric Power Company [Member]
Operating revenues
Electric operating revenues				2,152	2,181	2,124
Operating revenues from affiliates				6	5	5
Total operating revenues				2,158	2,186	2,129
Operating expenses
Purchased power				359	411	719
Purchased power from affiliate				255	295	0
Operating and maintenance				396	607	435
Operating and maintenance from affiliates				58	35	4
Depreciation and amortization				321	295	256
Taxes other than income				371	377	376
Total operating expenses				1,760	2,020	1,790
Gain (Loss) on Disposition of Other Assets				1	8	46
Operating Income (Loss)				399	174	385
Other income and (deductions)
Interest Expense				(121)	(127)	(124)
Other, net				32	36	28
Total other income and (deductions)				(89)	(91)	(96)
Income before income taxes				310	83	289
Income taxes				105	41	102
Income (Loss) from Equity Method Investments				0	0	0
Net Income (Loss)				205	42	187
Pension and non-pension postretirement benefit plans:
Comprehensive income				205	42	187
Delmarva Power and Light Company [Member]
Operating revenues
Electric operating revenues				1,131	1,122	1,132
Natural gas operating revenues				161	148	164
Operating revenues from affiliates				8	7	6
Total operating revenues				1,300	1,277	1,302
Operating expenses
Purchased power				282	369	555
Purchased fuel				71	60	79
Purchased power from affiliate				179	154	0
Operating and maintenance				283	422	303
Operating and maintenance from affiliates				32	19	1
Depreciation and amortization				167	157	148
Taxes other than income				57	55	51
Total operating expenses				1,071	1,236	1,137
Gain (Loss) on Disposition of Other Assets				0	9	0
Operating Income (Loss)				229	50	165
Other income and (deductions)
Interest Expense				(51)	(50)	(50)
Other, net				14	13	10
Total other income and (deductions)				(37)	(37)	(40)
Income before income taxes				192	13	125
Income taxes				71	22	49
Income (Loss) from Equity Method Investments				0	0	0
Net Income (Loss)				121	(9)	76
Pension and non-pension postretirement benefit plans:
Comprehensive income				121	(9)	76
Atlantic City Electric Company [Member]
Operating revenues
Electric operating revenues				1,184	1,254	1,291
Operating revenues from affiliates				2	3	4
Total operating revenues				1,186	1,257	1,295
Operating expenses
Purchased power				541	614	708
Purchased power from affiliate				29	37	0
Operating and maintenance				279	410	268
Operating and maintenance from affiliates				28	18	3
Depreciation and amortization				146	165	175
Taxes other than income				6	7	7
Total operating expenses				1,029	1,251	1,161
Gain (Loss) on Disposition of Other Assets				0	1	0
Operating Income (Loss)				157	7	134
Other income and (deductions)
Interest Expense				(61)	(62)	(64)
Other, net				7	9	3
Total other income and (deductions)				(54)	(53)	(61)
Income before income taxes				103	(46)	73
Income taxes				26	(4)	33
Income (Loss) from Equity Method Investments				0	0	0
Net Income (Loss)				77	(42)	40
Pension and non-pension postretirement benefit plans:
Comprehensive income				$ 77	$ (42)	$ 40

[1] Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 24 — Supplemental Financial Information for total utility taxes for the years ended December 31, 2017, 2016 and 2015.