Consolidated Statements of Operations and Comprehensive Income (Unaudited) - USD ($) shares in Millions, $ in Millions		3 Months Ended
	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 23, 2016
Operating revenues [Abstract]
Operating Revenue		$ 4,560	$ 4,473
Regulated Operating Revenue		4,197	3,100
Electric operating revenues		3,644	2,657
Natural gas operating revenues		553	444
Revenues		8,757	7,573
Operating expenses
Competitive businesses purchased power and fuel		2,795	2,440
Purchased power and fuel		1,104	814
Operating and maintenance		2,460	2,835
Depreciation and amortization		896	685
Taxes other than income		436	325
Total operating expenses		7,691	7,099
Gain (Loss) on Disposition of Other Assets		4	9
Bargain purchase gain		226	0
Operating income		1,296	483
Other income and (deductions)
Interest expense, net		(363)	(277)
Interest expense to affiliates		(10)	(10)
Other, net		283	114
Total other income and (deductions)		(90)	(173)
Income before income taxes		1,206	310
Income taxes		215	184
Equity in losses of unconsolidated affiliates		(10)	(3)
Net income		981	123
Net loss attributable to noncontrolling interests and preference stock dividends		(14)	(50)
Net income attributable to common shareholders		995	173
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost		(13)	(12)
Actuarial loss reclassified to periodic benefit cost		(49)	46
Pension and non-pension postretirement benefit plan valuation adjustment		(59)	1
Unrealized gain (loss) on cash flow hedges		6	7
Unrealized gain (loss) on equity investments		3	3
Unrealized gain on foreign currency translation		1	(6)
Unrealized gain (loss) on marketable securities		1	(1)
Other comprehensive (loss) income		(12)	28
Comprehensive income		969	151
Comprehensive loss attributable to noncontrolling interests and preference stock dividends		(16)	(50)
Comprehensive income attributable to common shareholders		$ 985	$ 201
Average shares of common stock outstanding:
Weighted average common shares outstanding — basic		928	923
Weighted average common shares outstanding — diluted		930	925
Earnings per average common share:
Basic		$ 1.07	$ 0.19
Diluted		1.07	0.19
Dividends declared per common share		$ 0.3275	$ 0.31
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating Revenue		$ 4,558	$ 4,471
Operating revenues from affiliates		330	268
Revenues		4,888	4,739
Operating expenses
Purchased power and fuel		2,796	2,440
Purchased power from affiliate		2	2
Operating and maintenance		1,309	1,296
Operating and maintenance from affiliates		179	171
Depreciation and amortization		302	289
Taxes other than income		143	126
Total operating expenses		4,731	4,324
Gain (Loss) on Disposition of Other Assets		4	0
Bargain purchase gain		226	0
Operating income		387	415
Other income and (deductions)
Interest expense, net		(90)	(87)
Interest expense to affiliates		(10)	(10)
Other, net		259	93
Total other income and (deductions)		159	(4)
Income before income taxes		546	411
Income taxes		127	151
Equity in losses of unconsolidated affiliates		(10)	(3)
Net income		409	257
Net loss attributable to noncontrolling interests		(14)	(53)
Net income attributable to membership interest		423	310
Other comprehensive income (loss), net of income taxes
Unrealized gain (loss) on cash flow hedges		(6)	5
Unrealized gain (loss) on equity investments		(4)	2
Unrealized gain on foreign currency translation		(1)	(6)
Other comprehensive (loss) income		11	(1)
Comprehensive income		420	256
Comprehensive loss attributable to noncontrolling interests and preference stock dividends		(16)	(53)
Comprehensive income attributable to common shareholders		436	309
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Electric operating revenues		1,293	1,244
Operating revenues from affiliates		5	5
Revenues		1,298	1,249
Operating expenses
Purchased power and fuel		329	343
Purchased power from affiliate		5	5
Operating and maintenance		307	305
Operating and maintenance from affiliates		63	63
Depreciation and amortization		208	189
Taxes other than income		72	75
Total operating expenses		984	980
Gain (Loss) on Disposition of Other Assets		0	5
Operating income		314	274
Other income and (deductions)
Interest expense, net		(82)	(83)
Interest expense to affiliates		(3)	(3)
Other, net		4	4
Total other income and (deductions)		(81)	(82)
Income before income taxes		233	192
Income taxes		92	77
Net income		141	115
Other comprehensive income (loss), net of income taxes
Comprehensive income		141	115
PECO Energy Co [Member]
Operating revenues [Abstract]
Electric operating revenues		589	643
Natural gas operating revenues		206	197
Operating revenues from affiliates		1	1
Revenues		796	841
Operating expenses
Purchased power		156	166
Purchased fuel		86	77
Purchased power from affiliate		45	78
Operating and maintenance		174	177
Operating and maintenance from affiliates		34	38
Depreciation and amortization		71	67
Taxes other than income		38	42
Total operating expenses		604	645
Operating income		192	196
Other income and (deductions)
Interest expense, net		(28)	(28)
Interest expense to affiliates		(3)	(3)
Other, net		2	2
Total other income and (deductions)		(29)	(29)
Income before income taxes		163	167
Income taxes		36	43
Net income		127	124
Other comprehensive income (loss), net of income taxes
Comprehensive income		127	124
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues		665	678
Natural gas operating revenues		281	246
Operating revenues from affiliates		5	5
Revenues		951	929
Operating expenses
Purchased power		133	127
Purchased fuel		83	75
Purchased power from affiliate		134	171
Operating and maintenance		148	168
Operating and maintenance from affiliates		35	34
Depreciation and amortization		128	109
Taxes other than income		62	58
Total operating expenses		723	742
Operating income		228	187
Other income and (deductions)
Interest expense, net		(23)	(20)
Interest expense to affiliates		(4)	(4)
Other, net		4	4
Total other income and (deductions)		(23)	(20)
Income before income taxes		205	167
Income taxes		80	66
Net income		125	101
Preference stock dividends		0	3
Net income attributable to common shareholders		125	98
Other comprehensive income (loss), net of income taxes
Comprehensive income		125	101
Comprehensive loss attributable to noncontrolling interests and preference stock dividends		0	3
Comprehensive income attributable to common shareholders		125	98
Pepco Holdings LLC [Member] | Predecessor [Member]
Operating revenues [Abstract]
Electric operating revenues				$ 1,096
Natural gas operating revenues				57
Operating revenues from affiliates				0
Revenues				1,153
Operating expenses
Purchased power and fuel				471
Purchased fuel				26
Purchased power from affiliate				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
Operating income				105
Other income and (deductions)
Interest expense, net				(65)
Other, net				(4)
Total other income and (deductions)				(69)
Income before income taxes				36
Income taxes				17
Net income				19
Other comprehensive income (loss), net of income taxes
Actuarial loss reclassified to periodic benefit cost				1
Other comprehensive (loss) income				1
Comprehensive income				$ 20
Pepco Holdings LLC [Member] | Successor [Member]
Operating revenues [Abstract]
Electric operating revenues	$ 90	1,097
Natural gas operating revenues	3	66
Operating revenues from affiliates	12	12
Revenues	105	1,175
Operating expenses
Purchased power and fuel	26	288
Purchased fuel	1	29
Purchased power from affiliate	11	144
Operating and maintenance	447	223
Operating and maintenance from affiliates	2	33
Depreciation and amortization	14	167
Taxes other than income	15	111
Total operating expenses	516	995
Operating income	(411)	180
Other income and (deductions)
Interest expense, net	(6)	(62)
Other, net	2	13
Total other income and (deductions)	(4)	(49)
Income before income taxes	(415)	131
Income taxes	(106)	(9)
Net income	(309)	140
Other comprehensive income (loss), net of income taxes
Actuarial loss reclassified to periodic benefit cost	0	0
Other comprehensive (loss) income	0	0
Comprehensive income	$ (309)	140
Potomac Electric Power Company [Member]
Operating revenues [Abstract]
Electric operating revenues		529	550
Operating revenues from affiliates		1	1
Revenues		530	551
Operating expenses
Purchased power and fuel		83	191
Purchased power from affiliate		83	6
Operating and maintenance		101	288
Operating and maintenance from affiliates		12	2
Depreciation and amortization		82	75
Taxes other than income		90	94
Total operating expenses		451	656
Operating income		79	(105)
Other income and (deductions)
Interest expense, net		(29)	(37)
Other, net		8	9
Total other income and (deductions)		(21)	(28)
Income before income taxes		58	(133)
Income taxes		0	(25)
Net income		58	(108)
Other comprehensive income (loss), net of income taxes
Comprehensive income		58	(108)
Delmarva Power and Light Company [Member]
Operating revenues [Abstract]
Electric operating revenues		294	301
Natural gas operating revenues		66	59
Operating revenues from affiliates		2	2
Revenues		362	362
Operating expenses
Purchased power		77	147
Purchased fuel		29	25
Purchased power from affiliate		51	4
Operating and maintenance		66	204
Operating and maintenance from affiliates		7	0
Depreciation and amortization		39	39
Taxes other than income		15	15
Total operating expenses		284	434
Operating income		78	(72)
Other income and (deductions)
Interest expense, net		(13)	(12)
Other, net		3	3
Total other income and (deductions)		(10)	(9)
Income before income taxes		68	(81)
Income taxes		11	(9)
Net income		57	(72)
Other comprehensive income (loss), net of income taxes
Comprehensive income		57	(72)
Atlantic City Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues		274	290
Operating revenues from affiliates		1	1
Revenues		275	291
Operating expenses
Purchased power and fuel		128	157
Purchased power from affiliate		9	1
Operating and maintenance		69	211
Operating and maintenance from affiliates		7	1
Depreciation and amortization		35	40
Taxes other than income		2	2
Total operating expenses		250	412
Operating income		25	(121)
Other income and (deductions)
Interest expense, net		(15)	(16)
Other, net		2	4
Total other income and (deductions)		(13)	(12)
Income before income taxes		12	(133)
Income taxes		(16)	(33)
Net income		28	(100)
Other comprehensive income (loss), net of income taxes
Comprehensive income		$ 28	$ (100)