Consolidated Statements of Operations and Comprehensive Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Operating revenues [Abstract]
Operating revenues			$ 16,324	$ 18,395		$ 16,637
Rate-regulated utility revenues			15,036	11,052		10,792
Electric operating revenues			13,869	9,876		9,467
Natural gas operating revenues			1,166	1,176		1,325
Operating revenues from affiliates			10	9		23
Total operating revenues			31,360	29,447		27,429
Operating expenses
Competitive businesses purchased power and fuel			8,817	10,007		9,369
Purchased power and fuel			3,823	3,077		3,103
Related Party Transaction, Purchases from Related Party			0	0		531
Purchased power			0	0		531
Operating and maintenance			10,048	8,322		8,568
Depreciation and amortization			3,936	2,450		2,314
Taxes other than income			1,576	1,200		1,154
Total operating expenses			28,200	25,056		25,039
Equity in losses of unconsolidated affiliates			(24)	(7)		0
Gain (Loss) on Disposition of Other Assets			(48)	18		437
Gain on consolidation and acquisition of businesses			0	0		289
Operating Income (Loss)			3,112	4,409		3,096
Other income and (deductions)
Interest Expense			(1,495)	(992)		(1,024)
Interest expense to affiliates			(41)	(41)		(41)
Other, net			413	(46)		455
Total other income and (deductions)			(1,123)	(1,079)		(610)
Income before income taxes			1,989	3,330		2,486
Income before income taxes			1,989	3,330		2,486
Income taxes			761	1,073		666
Net Income (Loss) Attributable to Noncontrolling Interest			70	(19)		197
Net Income			1,204	2,250		1,820
Net income attributable to common shareholders			1,134	2,269		1,623
Pension and non-pension postretirement benefit plans:
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions			0	0		(20)
Prior service benefit reclassified to periodic benefit cost, net of tax			(48)	(46)		(30)
Actuarial loss reclassified to periodic cost, net of tax			184	220		147
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax			181	99		497
Unrealized gain (loss) on cash flow hedges, net of taxes	$ 0		(2)	(9)		148
Unrealized gain (loss) on marketable securities, net of taxes			(4)	(3)		8
Unrealized gain (loss) on foreign currency translation, net of taxes			10	(21)		(9)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax			1	0		1
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease			0	0		(116)
Other comprehensive income (loss)			(36)	60	[1]	(644)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest			1,168	2,310		1,176
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest			70	(19)		197
Comprehensive income			$ 1,098	$ 2,329		$ 979
Average shares of common stock outstanding:
Basic			924	890		860
Diluted			927	893		864
Earnings per average common share:
Basic (in usd per share)			$ 1.23	$ 2.55		$ 1.89
Diluted (in usd per share)			1.22	2.54		1.88
Dividends per common share (in usd per share)			$ 1.264	$ 1.24		$ 1.24
Predecessor [Member]
Operating expenses
Gain (Loss) on Disposition of Other Assets	0					$ 0
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating revenues			$ 16,312	$ 18,386		16,614
Operating revenues from affiliates			1,439	749		779
Total operating revenues			17,751	19,135		17,393
Operating expenses
Purchased power and fuel			8,818	10,007		9,368
Related Party Transaction, Purchases from Related Party			12	14		557
Purchased power			12	14		557
Operating and maintenance			4,978	4,688		4,943
Operating and maintenance from affiliates			663	620		623
Depreciation and amortization			1,879	1,054		967
Taxes other than income			506	489		465
Total operating expenses			16,856	16,872		16,923
Equity in losses of unconsolidated affiliates			0	0		(20)
Gain (Loss) on Disposition of Other Assets			(59)	12		437
Gain on consolidation and acquisition of businesses			0	0		289
Operating Income (Loss)			836	2,275		1,176
Other income and (deductions)
Interest Expense			(325)	(322)		(303)
Interest expense to affiliates			(39)	(43)		(53)
Other, net			401	(60)		406
Total other income and (deductions)			37	(425)		50
Income (Loss) Attributable to Noncontrolling Interest			62	(32)		184
Income before income taxes			873	1,850		1,226
Income taxes			290	502		207
Net Income			558	1,340		1,019
Net income attributable to membership interest			496	1,372		835
Pension and non-pension postretirement benefit plans:
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions			(25)	(8)		0
Unrealized gain (loss) on cash flow hedges, net of taxes			(2)	3		132
Unrealized gain (loss) on marketable securities, net of taxes			(4)	(3)		8
Unrealized gain (loss) on foreign currency translation, net of taxes			10	(21)		(9)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax			1	0		(1)
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease			0	0
Other comprehensive income (loss)			9	(27)	[1]	(250)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest			567	1,313		769
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest			62	(32)		184
Comprehensive income			505	1,345		585
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Electric operating revenues			5,239	4,901		4,560
Operating revenues from affiliates			15	4		4
Total operating revenues			5,254	4,905		4,564
Operating expenses
Related Party Transaction, Purchases from Related Party			47	18		176
Purchased power			1,411	1,301		1,001
Operating and maintenance			1,303	1,372		1,263
Operating and maintenance from affiliates			227	195		166
Depreciation and amortization			775	707		687
Taxes other than income			293	296		293
Total operating expenses			4,056	3,889		3,586
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			7	1		2
Operating Income (Loss)			1,205	1,017		980
Other income and (deductions)
Interest Expense			(448)	(319)		(308)
Interest expense to affiliates			(13)	(13)		(13)
Other, net			(65)	21		17
Total other income and (deductions)			(526)	(311)		(304)
Income before income taxes			679	706		676
Income taxes			301	280		268
Net Income			378	426		408
Pension and non-pension postretirement benefit plans:
Comprehensive income			378	426		408
PECO Energy Co [Member]
Operating revenues [Abstract]
Electric operating revenues			2,524	2,485		2,446
Natural gas operating revenues			462	545		646
Operating revenues from affiliates			8	2		2
Total operating revenues			2,994	3,032		3,094
Operating expenses
Related Party Transaction, Purchases from Related Party			287	220		194
Purchased power			598	735		740
Purchased fuel			162	235		327
Operating and maintenance			665	684		767
Operating and maintenance from affiliates			146	110		99
Depreciation and amortization			270	260		236
Taxes other than income			164	160		159
Total operating expenses			2,292	2,404		2,522
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			0	2		0
Operating Income (Loss)			702	630		572
Other income and (deductions)
Interest Expense			(111)	(102)		(101)
Interest expense to affiliates			(12)	(12)		(12)
Other, net			8	5		7
Total other income and (deductions)			(115)	(109)		(106)
Income before income taxes			587	521		466
Income taxes			149	143		114
Net Income			438	378		352
Net income attributable to common shareholders			438	378		352
Pension and non-pension postretirement benefit plans:
Comprehensive income			438	378		352
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues			2,603	2,490		2,460
Natural gas operating revenues			609	631		680
Operating revenues from affiliates			21	14		25
Total operating revenues			3,233	3,135		3,165
Operating expenses
Related Party Transaction, Purchases from Related Party			604	498		382
Purchased power			528	602		733
Purchased fuel			162	205		302
Operating and maintenance			605	565		614
Operating and maintenance from affiliates			132	118		103
Depreciation and amortization			423	366		371
Taxes other than income			229	224		221
Total operating expenses			2,683	2,578		2,726
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			0	1		0
Operating Income (Loss)			550	558		439
Other income and (deductions)
Interest Expense			(87)	(83)		(90)
Interest expense to affiliates			(16)	(16)		(16)
Other, net			21	18		18
Total other income and (deductions)			(82)	(81)		(88)
Income before income taxes			468	477		351
Income taxes			174	189		140
Net Income			294	288		211
Dividends, Preferred Stock			8	13		13
Net income attributable to common shareholders			286	275		198
Pension and non-pension postretirement benefit plans:
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest			294	288		211
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest			8	13		13
Comprehensive income			286	275		198
Pepco Holdings LLC [Member]
Operating expenses
Related Party Transaction, Purchases from Related Party	0			0		0
Pepco Holdings LLC [Member] | Predecessor [Member]
Operating revenues [Abstract]
Electric operating revenues	1,096			4,770		4,614
Natural gas operating revenues	57			165		194
Operating revenues from affiliates	0			0		0
Total operating revenues	1,153			4,935		4,808
Operating expenses
Purchased power	471			1,986		1,940
Purchased fuel	26			87		117
Operating and maintenance	294			1,156		1,183
Operating and maintenance from affiliates	0			0		0
Depreciation and amortization	152			624		526
Taxes other than income	105			455		437
Total operating expenses	1,048			4,308		4,203
Equity in losses of unconsolidated affiliates	0			0
Gain (Loss) on Disposition of Other Assets				46
Operating Income (Loss)	105			673		605
Other income and (deductions)
Interest Expense	(65)			(280)		(269)
Other, net	(4)			88		44
Total other income and (deductions)	(69)			(192)		(225)
Income before income taxes	36			481		380
Income taxes	17			163		138
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest	0			9		0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	19			318		242
Net Income	19			327		242
Net income attributable to membership interest	19			327		242
Pension and non-pension postretirement benefit plans:
Actuarial loss reclassified to periodic cost, net of tax	1			9		(12)
Unrealized gain (loss) on cash flow hedges, net of taxes				(1)		0
Other comprehensive income (loss)	1			10	[1]	(12)
Comprehensive income	20			337		230
Pepco Holdings LLC [Member] | Successor [Member]
Operating revenues [Abstract]
Electric operating revenues		$ 3,506
Natural gas operating revenues		92
Operating revenues from affiliates		45
Total operating revenues		3,643
Operating expenses
Related Party Transaction, Purchases from Related Party		486
Purchased power		925
Purchased fuel		36
Operating and maintenance		1,144
Operating and maintenance from affiliates		89
Depreciation and amortization		515
Taxes other than income		354
Total operating expenses		3,549
Equity in losses of unconsolidated affiliates		0
Gain (Loss) on Disposition of Other Assets		(1)
Operating Income (Loss)		93
Other income and (deductions)
Interest Expense		(195)
Other, net		44
Total other income and (deductions)		(151)
Income before income taxes		(58)
Income taxes		3
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest	$ 0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest		(61)
Net Income (Loss) Attributable to Noncontrolling Interest		(61)
Net Income		(61)
Net income attributable to membership interest		(61)
Pension and non-pension postretirement benefit plans:
Actuarial loss reclassified to periodic cost, net of tax		0
Unrealized gain (loss) on cash flow hedges, net of taxes		0
Other comprehensive income (loss)		0
Comprehensive income		$ (61)
Delmarva Power and Light Company [Member]
Operating revenues [Abstract]
Electric operating revenues			1,122	1,132		1,081
Natural gas operating revenues			148	164		194
Operating revenues from affiliates			7	6		7
Total operating revenues			1,277	1,302		1,282
Operating expenses
Related Party Transaction, Purchases from Related Party			154	0		0
Purchased power			369	555		536
Purchased fuel			60	79		104
Operating and maintenance			422	303		266
Operating and maintenance from affiliates			19	1		1
Depreciation and amortization			157	148		122
Taxes other than income			55	51		46
Total operating expenses			1,236	1,137		1,075
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			9	0		0
Operating Income (Loss)			50	165		207
Other income and (deductions)
Interest Expense			(50)	(50)		(48)
Other, net			13	10		10
Total other income and (deductions)			(37)	(40)		(38)
Income before income taxes			13	125		169
Income taxes			22	49		65
Net Income			(9)	76		104
Net income attributable to common shareholders			(9)	76		104
Pension and non-pension postretirement benefit plans:
Comprehensive income			(9)	76		104
Potomac Electric Power Company [Member]
Operating revenues [Abstract]
Electric operating revenues			2,181	2,124		2,050
Operating revenues from affiliates			5	5		5
Total operating revenues			2,186	2,129		2,055
Operating expenses
Related Party Transaction, Purchases from Related Party			295	0		0
Purchased power			411	719		735
Operating and maintenance			607	435		386
Operating and maintenance from affiliates			35	4		4
Depreciation and amortization			295	256		212
Taxes other than income			377	376		369
Total operating expenses			2,020	1,790		1,706
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			8	46		0
Operating Income (Loss)			174	385		349
Other income and (deductions)
Interest Expense			(127)	(124)		(115)
Other, net			36	28		30
Total other income and (deductions)			(91)	(96)		(85)
Income before income taxes			83	289		264
Income taxes			41	102		93
Net Income			42	187		171
Net income attributable to common shareholders			42	187		171
Pension and non-pension postretirement benefit plans:
Comprehensive income			42	187		171
Atlantic City Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues			1,254	1,291		1,206
Operating revenues from affiliates			3	4		4
Total operating revenues			1,257	1,295		1,210
Operating expenses
Purchased power			614	708		664
Cost Of Goods And Services Energy Commodities And Services From Affiliate			37	0		0
Operating and maintenance			410	268		247
Operating and maintenance from affiliates			18	3		3
Depreciation and amortization			165	175		155
Taxes other than income			7	7		4
Total operating expenses			1,251	1,161		1,073
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			1	0		0
Operating Income (Loss)			7	134		137
Other income and (deductions)
Interest Expense			(62)	(64)		(64)
Other, net			9	3		3
Total other income and (deductions)			(53)	(61)		(61)
Income before income taxes			(46)	73		76
Income taxes			(4)	33		30
Net Income			(42)	40		46
Net income attributable to common shareholders			(42)	40		46
Pension and non-pension postretirement benefit plans:
Comprehensive income			$ (42)	$ 40		$ 46

[1] All amounts are net of tax and noncontrolling interests. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.