Consolidated Statements of Operations and Comprehensive Income (Unaudited) - USD ($) shares in Millions, $ in Millions			3 Months Ended
		Mar. 31, 2016	Mar. 31, 2016	Mar. 23, 2016	Mar. 31, 2015
Operating revenues [Abstract]
Electrical Generation Revenue			$ 4,473		$ 5,632
Gas Domestic Regulated Revenue			444		624
Regulated Operating Revenue			3,100		3,198
Electric Revenue			2,657		2,574
Revenues			7,573		8,830
Operating expenses
Purchased power			2,440		3,426
Purchased power and fuel			814		1,044
Operating and maintenance			2,835		2,081
Depreciation and amortization			685		610
Taxes other than income			325		304
Total operating expenses			7,099		7,465
Equity in (losses) earnings of unconsolidated affiliates			3
Gain (Loss) on Sale of Assets and Asset Impairment Charges			9		1
Operating income			483		1,366
Other income and (deductions)
Interest expense, net			(277)		(335)
Interest expense to affiliates, net			(10)		(10)
Other, net			(114)		(80)
Total other income and (deductions)			(173)		(265)
Income before income taxes			310		1,101
Income taxes			184		363
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions			(3)		0
Net income			123		738
Net (loss) income attributable to noncontrolling interest and preference stock dividends			(50)		45
Net income attributable to common shareholders			173		693
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost			(12)		(11)
Actuarial loss reclassified to periodic benefit cost			46		54
Pension and non-pension postretirement benefit plan valuation adjustment			(1)		(26)
Unrealized (loss) gain on cash flow hedges			(7)		6
Unrealized loss on equity investments			(3)		0
Unrealized loss on marketable securities			(1)		0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax			6		(12)
Other comprehensive income	[1]		28		11
Comprehensive income			$ 151		$ 749
Average shares of common stock outstanding:
Weighted average common shares outstanding — basic			923		862
Average common shares outstanding — diluted			925		867
Earnings per average common share:
Earnings per share - basic (in usd per share)			$ 0.19		$ 0.80
Earnings per average common share - diluted
Earnings per share - diluted (in usd per share)			0.19		0.80
Dividends per common share (in usd per share)			$ 0.31		$ 0.31
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Electrical Generation Revenue			$ 4,471		$ 5,629
Operating revenues from affiliates			268		211
Revenues			4,739		5,840
Operating expenses
Purchased power and fuel			2,440		3,426
Purchased power and fuel from affiliates			2		7
Operating and maintenance			1,296		1,162
Operating and maintenance from affiliates			171		149
Depreciation and amortization			289		254
Taxes other than income			126		122
Total operating expenses			4,324		5,120
Equity in (losses) earnings of unconsolidated affiliates			3
Gain (Loss) on Sale of Assets and Asset Impairment Charges			0		(1)
Operating income			415		719
Other income and (deductions)
Interest expense, net			(87)		(90)
Interest expense to affiliates, net			(10)		(12)
Other, net			(93)		(94)
Total other income and (deductions)			(4)		(8)
Income before income taxes			411		711
Income taxes			151		226
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions			(3)		0
Net income			257		485
Net (loss) income attributable to noncontrolling interests			(53)		42
Net income attributable to membership interest			310		443
Pension and non-pension postretirement benefit plans:
Unrealized (loss) gain on cash flow hedges			(5)		(5)
Unrealized loss on equity investments			(2)		0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax			6		(12)
Other comprehensive income	[1]		(1)		(17)
Comprehensive income			256		468
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Operating revenues			1,244		1,184
Operating revenues from affiliates			5		1
Revenues			1,249		1,185
Operating expenses
Purchased power and fuel			343		318
Purchased power and fuel from affiliates			5		9
Operating and maintenance			305		333
Operating and maintenance from affiliates			63		45
Depreciation and amortization			189		175
Taxes other than income			75		75
Total operating expenses			980		955
Equity in (losses) earnings of unconsolidated affiliates			0
Gain (Loss) on Sale of Assets and Asset Impairment Charges			5		0
Operating income			274		230
Other income and (deductions)
Interest expense, net			(83)		(81)
Interest expense to affiliates, net			(3)		(3)
Other, net			(4)		(3)
Total other income and (deductions)			(82)		(81)
Income before income taxes			192		149
Income taxes			77		59
Net income			115		90
Pension and non-pension postretirement benefit plans:
Comprehensive income			115		90
PECO Energy Co [Member]
Operating revenues [Abstract]
Gas Domestic Regulated Revenue			197		308
Operating revenues from affiliates			1		0
Electric Revenue			643		677
Revenues			841		985
Operating expenses
Utilities Operating Expense, Purchased Power			166		216
Purchased power and fuel from affiliates			78		62
Utilities Operating Expense, Purchased Power			77		160
Operating and maintenance			177		197
Operating and maintenance from affiliates			38		25
Depreciation and amortization			67		62
Taxes other than income			42		41
Total operating expenses			645		763
Gain (Loss) on Disposition of Other Assets			0		1
Equity in (losses) earnings of unconsolidated affiliates			0
Operating income			196		223
Other income and (deductions)
Interest expense, net			(28)		(25)
Interest expense to affiliates, net			(3)		(3)
Other, net			(2)		(2)
Total other income and (deductions)			(29)		(26)
Income before income taxes			167		197
Income taxes			43		58
Net income			124		139
Pension and non-pension postretirement benefit plans:
Comprehensive income			124		139
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Gas Domestic Regulated Revenue			246		315
Operating revenues from affiliates			5		7
Electric Revenue			678		714
Revenues			929		1,036
Operating expenses
Utilities Operating Expense, Purchased Power			127		208
Purchased power and fuel from affiliates			171		137
Utilities Operating Expense, Purchased Power			75		142
Operating and maintenance			168		156
Operating and maintenance from affiliates			34		26
Depreciation and amortization			109		106
Taxes other than income			58		57
Total operating expenses			742		832
Equity in (losses) earnings of unconsolidated affiliates			0
Operating income			187		204
Other income and (deductions)
Interest expense, net			(20)		(21)
Interest expense to affiliates, net			(4)		(4)
Other, net			(4)		(4)
Total other income and (deductions)			(20)		(21)
Income before income taxes			167		183
Income taxes			66		74
Net income			101		109
Preferred security dividends and redemption			3		3
Net income attributable to common shareholders			98		106
Pension and non-pension postretirement benefit plans:
Comprehensive income			101		109
Pepco Holdings, LLC [Member] | Predecessor [Member]
Electric and Gas Revenue				$ 1,096	1,268
Operating revenues [Abstract]
Gas Domestic Regulated Revenue				57	86
Operating revenues from affiliates				0	0
Revenues				1,153	1,354
Operating expenses
Purchased power and fuel				471	588
Utilities Operating Expense, Purchased Power				26	51
Operating and maintenance				294	300
Operating and maintenance from affiliates				0	0
Depreciation and amortization				152	155
Taxes other than income				105	118
Total operating expenses				1,048	1,212
Operating income				105	142
Other income and (deductions)
Interest expense, net				(65)	(68)
Other, net				4	(9)
Total other income and (deductions)				(69)	(59)
Income before income taxes				36	83
Income taxes				17	30
Net income				19	53
Pension and non-pension postretirement benefit plans:
Actuarial loss reclassified to periodic benefit cost				1	1
Other comprehensive income				1	1
Comprehensive income				$ 20	54
Pepco Holdings, LLC [Member] | Successor [Member]
Electric and Gas Revenue		$ 90
Operating revenues [Abstract]
Gas Domestic Regulated Revenue		3
Operating revenues from affiliates		12
Revenues		105
Operating expenses
Purchased power and fuel		26
Utilities Operating Expense, Purchased Power		1
Operating and maintenance		447
Costs and Expenses, Related Party		2
Operating and maintenance from affiliates		11
Depreciation and amortization		14
Taxes other than income		15
Total operating expenses		516
Operating income		(411)
Other income and (deductions)
Interest expense, net		(6)
Other, net		(2)
Total other income and (deductions)		(4)
Income before income taxes		(415)
Income taxes		(106)
Net income		(309)
Pension and non-pension postretirement benefit plans:
Actuarial loss reclassified to periodic benefit cost		0
Other comprehensive income		0
Comprehensive income		$ (309)
Potomac Electric Power Company [Member]
Operating revenues [Abstract]
Operating revenues from affiliates			1		1
Electric Revenue			550		544
Revenues			551		545
Operating expenses
Purchased power and fuel			191		211
Purchased power and fuel from affiliates			6		0
Operating and maintenance			288		112
Operating and maintenance from affiliates			2		1
Depreciation and amortization			75		62
Taxes other than income			94		96
Total operating expenses			656		482
Equity in (losses) earnings of unconsolidated affiliates			0
Operating income			(105)		63
Other income and (deductions)
Interest expense, net			(37)		(30)
Other, net			(9)		(5)
Total other income and (deductions)			(28)		(25)
Income before income taxes			(133)		38
Income taxes			(25)		12
Net income			(108)		26
Pension and non-pension postretirement benefit plans:
Comprehensive income			(108)		26
Delmarva Power and Light Company [Member]
Operating revenues [Abstract]
Gas Domestic Regulated Revenue			59		86
Operating revenues from affiliates			2		2
Electric Revenue			301		333
Revenues			362		421
Operating expenses
Utilities Operating Expense, Purchased Power			147		178
Purchased power and fuel from affiliates					0
Utilities Operating Expense, Purchased Power			25		47
Operating and maintenance			204		81
Operating and maintenance from affiliates			4
Depreciation and amortization			39		39
Taxes other than income			15		13
Total operating expenses			434		358
Equity in (losses) earnings of unconsolidated affiliates			0
Operating income			(72)		63
Other income and (deductions)
Interest expense, net			(12)		(12)
Other, net			(3)		(2)
Total other income and (deductions)			(9)		(10)
Income before income taxes			(81)		53
Income taxes			(9)		21
Net income			(72)		32
Pension and non-pension postretirement benefit plans:
Comprehensive income			(72)		32
Atlantic City Electric Company [Member]
Operating revenues [Abstract]
Operating revenues from affiliates			1		1
Electric Revenue			290		333
Revenues			291		334
Operating expenses
Purchased power and fuel			157		191
Purchased power and fuel from affiliates			1		0
Operating and maintenance			211		68
Operating and maintenance from affiliates			1		1
Depreciation and amortization			40		43
Taxes other than income			2		2
Total operating expenses			412		305
Equity in (losses) earnings of unconsolidated affiliates			0
Operating income			(121)		29
Other income and (deductions)
Interest expense, net			(16)		(16)
Other, net			(4)		(1)
Total other income and (deductions)			(12)		(15)
Income before income taxes			(133)		14
Income taxes			(33)		5
Net income			(100)		9
Pension and non-pension postretirement benefit plans:
Comprehensive income			$ (100)		$ 9

[1] All amounts are net of tax. Amounts in parenthesis represent a decrease in AOCI.