Consolidated Statements of Operations and Comprehensive Income (Unaudited) - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Operating revenues [Abstract]
Operating Revenue		$ 5,113	$ 4,550
Regulated Operating Revenue		4,570	4,118
Electric operating revenues			0
Natural gas operating revenues			0
Revenues from alternative revenue programs		10	79
Operating revenues from affiliates	[1]	0	0
Revenues		9,693	8,747
Operating expenses
Competitive businesses purchased power and fuel		3,289	2,795
Cost of Purchased Power		1,438	1,104
Operating and maintenance		2,384	2,438
Depreciation and amortization		1,091	896
Taxes other than income		446	436
Total operating expenses		8,648	7,669
Gain (Loss) on Disposition of Other Assets		56	4
Bargain purchase gain		0	226
Operating income		1,101	1,308
Other income and (deductions)
Interest expense, net		(365)	(363)
Interest expense to affiliates		(6)	(10)
Other, net		(28)	257
Total other income and (deductions)		(399)	(116)
Income before income taxes		702	1,192
Income taxes		59	211
Equity in losses of unconsolidated affiliates		(7)	(10)
Net income		636	971
Net income (loss) attributable to noncontrolling interests		51	(19)
Net income attributable to common shareholders		585	990
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost		(17)	(13)
Actuarial loss reclassified to periodic benefit cost		61	49
Pension and non-pension postretirement benefit plan valuation adjustment		18	(59)
Unrealized gain on cash flow hedges		8	6
Other Comprehensive Income Unrealized Income Loss On Equity Investments Arising During Period Net Of Tax		1	3
Unrealized gain on foreign currency translation		1	1
Unrealized gain on marketable securities		0	1
Other comprehensive income (loss)		72	(12)
Comprehensive income		708	959
Comprehensive income (loss) attributable to noncontrolling interests		52	(21)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent		$ 656	$ 980
Average shares of common stock outstanding:
Weighted average common shares outstanding — basic		966	928
Weighted average common shares outstanding — diluted		968	930
Earnings per average common share:
Basic		$ 0.61	$ 1.07
Diluted		0.60	1.06
Dividends declared per common share		$ 0.35	$ 0.33
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating Revenue		$ 5,114	$ 4,548
Regulated Operating Revenue			0
Electric operating revenues			0
Natural gas operating revenues			0
Revenues from alternative revenue programs			0
Operating revenues from affiliates		398	330
Revenues		5,512	4,878
Operating expenses
Cost of Purchased Power		3,289	2,796
Purchased power from affiliate		4	2
Operating and maintenance		1,178	1,313
Operating and maintenance from affiliates		161	179
Depreciation and amortization		448	302
Taxes other than income		138	143
Total operating expenses		5,218	4,735
Gain (Loss) on Disposition of Other Assets		53	4
Bargain purchase gain		0	226
Operating income		347	373
Other income and (deductions)
Interest expense, net		(91)	(90)
Interest expense to affiliates		(10)	(10)
Other, net		(44)	259
Total other income and (deductions)		(145)	159
Income before income taxes		202	532
Income taxes		9	123
Equity in losses of unconsolidated affiliates		(7)	(10)
Net income		186	399
Net income (loss) attributable to noncontrolling interests		50	(19)
Net income attributable to membership interest		136	418
Other comprehensive income (loss), net of income taxes
Unrealized gain on cash flow hedges		7	6
Other Comprehensive Income Unrealized Income Loss On Equity Investments Arising During Period Net Of Tax		1	4
Unrealized gain on foreign currency translation		(1)	1
Other comprehensive income (loss)		7	11
Comprehensive income		193	410
Comprehensive income (loss) attributable to noncontrolling interests		51	(21)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent		142	431
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Operating Revenue			0
Regulated Operating Revenue			0
Electric operating revenues		1,493	1,279
Natural gas operating revenues			0
Revenues from alternative revenue programs		5	14
Operating revenues from affiliates		14	5
Revenues		1,512	1,298
Operating expenses
Purchased power		411	329
Purchased power from affiliate		194	5
Operating and maintenance		253	307
Operating and maintenance from affiliates		60	63
Depreciation and amortization		228	208
Taxes other than income		77	72
Total operating expenses		1,223	984
Gain (Loss) on Disposition of Other Assets		3	0
Operating income		292	314
Other income and (deductions)
Interest expense, net		(86)	(82)
Interest expense to affiliates		(3)	(3)
Other, net		8	4
Total other income and (deductions)		(81)	(81)
Income before income taxes		211	233
Income taxes		46	92
Net income		165	141
Other comprehensive income (loss), net of income taxes
Comprehensive income		165	141
PECO Energy Co [Member]
Operating revenues [Abstract]
Operating Revenue			0
Regulated Operating Revenue			0
Electric operating revenues		633	589
Natural gas operating revenues		232	206
Revenues from alternative revenue programs		(1)	0
Operating revenues from affiliates		2	1
Revenues		866	796
Operating expenses
Purchased power		199	156
Purchased fuel		98	86
Purchased power from affiliate		36	45
Operating and maintenance		233	174
Operating and maintenance from affiliates		42	34
Depreciation and amortization		75	71
Taxes other than income		41	38
Total operating expenses		724	604
Operating income		142	192
Other income and (deductions)
Interest expense, net		(30)	(28)
Interest expense to affiliates		(3)	(3)
Other, net		2	2
Total other income and (deductions)		(31)	(29)
Income before income taxes		111	163
Income taxes		(2)	36
Net income		113	127
Other comprehensive income (loss), net of income taxes
Comprehensive income		113	127
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Operating Revenue			0
Regulated Operating Revenue			0
Electric operating revenues		654	640
Natural gas operating revenues		330	271
Revenues from alternative revenue programs		(13)	35
Operating revenues from affiliates		6	5
Revenues		977	951
Operating expenses
Purchased power		192	133
Purchased fuel		123	83
Purchased power from affiliate		65	134
Operating and maintenance		184	148
Operating and maintenance from affiliates		37	35
Depreciation and amortization		134	128
Taxes other than income		65	62
Total operating expenses		800	723
Operating income		177	228
Other income and (deductions)
Interest expense, net		(25)	(23)
Interest expense to affiliates		0	(4)
Other, net		4	4
Total other income and (deductions)		(21)	(23)
Income before income taxes		156	205
Income taxes		28	80
Net income		128	125
Other comprehensive income (loss), net of income taxes
Comprehensive income		128	125
Pepco Holdings LLC [Member]
Operating revenues [Abstract]
Operating Revenue			0
Regulated Operating Revenue			0
Electric operating revenues		1,151	1,067
Natural gas operating revenues		78	66
Revenues from alternative revenue programs		18	30
Operating revenues from affiliates		4	12
Revenues		1,251	1,175
Operating expenses
Purchased power		374	288
Purchased fuel		41	29
Purchased power from affiliate		105	144
Operating and maintenance		271	223
Operating and maintenance from affiliates		38	33
Depreciation and amortization		183	167
Taxes other than income		113	111
Total operating expenses		1,125	995
Operating income		126	180
Other income and (deductions)
Interest expense, net		(63)	(62)
Other, net		11	13
Total other income and (deductions)		(52)	(49)
Income before income taxes		74	131
Income taxes		9	(9)
Net income		65	140
Other comprehensive income (loss), net of income taxes
Comprehensive Income (Loss), Net of Tax, Attributable to Parent		65	140
Potomac Electric Power Company [Member]
Operating revenues [Abstract]
Operating Revenue			0
Regulated Operating Revenue			0
Electric operating revenues		536	514
Natural gas operating revenues			0
Revenues from alternative revenue programs		19	15
Operating revenues from affiliates		2	1
Revenues		557	530
Operating expenses
Purchased power		130	83
Purchased power from affiliate		52	83
Operating and maintenance		73	101
Operating and maintenance from affiliates		57	12
Depreciation and amortization		96	82
Taxes other than income		93	90
Total operating expenses		501	451
Operating income		56	79
Other income and (deductions)
Interest expense, net		(31)	(29)
Other, net		8	8
Total other income and (deductions)		(23)	(21)
Income before income taxes		33	58
Income taxes		2	0
Net income		31	58
Other comprehensive income (loss), net of income taxes
Comprehensive income		31	58
Delmarva Power and Light Company [Member]
Operating revenues [Abstract]
Operating Revenue			0
Regulated Operating Revenue			0
Electric operating revenues		303	285
Natural gas operating revenues		78	66
Revenues from alternative revenue programs		1	9
Operating revenues from affiliates		2	2
Revenues		384	362
Operating expenses
Purchased power		90	77
Purchased fuel		41	29
Purchased power from affiliate		46	51
Operating and maintenance		57	66
Operating and maintenance from affiliates		41	7
Depreciation and amortization		45	39
Taxes other than income		15	15
Total operating expenses		335	284
Operating income		49	78
Other income and (deductions)
Interest expense, net		(13)	(13)
Other, net		2	3
Total other income and (deductions)		(11)	(10)
Income before income taxes		38	68
Income taxes		7	11
Net income		31	57
Other comprehensive income (loss), net of income taxes
Comprehensive Income (Loss), Net of Tax, Attributable to Parent		31	57
Atlantic City Electric Company [Member]
Operating revenues [Abstract]
Operating Revenue			0
Regulated Operating Revenue			0
Electric operating revenues		311	268
Natural gas operating revenues			0
Revenues from alternative revenue programs		(2)	6
Operating revenues from affiliates		1	1
Revenues		310	275
Operating expenses
Purchased power		155	128
Purchased power from affiliate		6	9
Operating and maintenance		54	69
Operating and maintenance from affiliates		36	7
Depreciation and amortization		33	35
Taxes other than income		3	2
Total operating expenses		287	250
Operating income		23	25
Other income and (deductions)
Interest expense, net		(16)	(15)
Other, net		1	2
Total other income and (deductions)		(15)	(13)
Income before income taxes		8	12
Income taxes		1	(16)
Net income		7	28
Other comprehensive income (loss), net of income taxes
Comprehensive income		$ 7	$ 28

[1] Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.