Regulatory Matters Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015	Sep. 30, 2016		Sep. 30, 2015	Dec. 31, 2015
Regulatory Assets [Line Items]
Current		$ 1,410			$ 1,410			$ 759
Noncurrent		10,022			10,022			6,065
Regulatory Assets		11,432			11,432			6,824
Regulatory Liabilities		4,985			4,985			4,570
Business Combination, Integration Related Costs		20		$ 22	123		$ 84
Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4,096	[1]		4,096	[1]		3,156
Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,973			1,973			1,616
AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		704			704			399
Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		232			232			189
Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		126			126			47
Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		828			828			162	[2]
Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Current		1,206			1,206
Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6			6			9
Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		108			108			108
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		295			295			286
Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		58			58			52
Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		246			246			247
Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		74			74			84
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		39			39			2
Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		13			13			20
Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		25			25			87
Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		642			642			279
Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		23			23			6
ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets								3
Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		45			45			29
Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9			9			30
Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9			9			0
Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		30			30			0
Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		37			37			6
Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		153			153			0
CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7			7			7
AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		448			448
Under funded Benefit Post Retirement Obligation [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,087			1,087
Commonwealth Edison Co [Member]
Regulatory Assets [Line Items]
Current		205			205			218
Noncurrent		987			987			895
Regulatory Assets		1,192			1,192			1,113
Regulatory Liabilities		3,781			3,781			3,614
Business Combination, Integration Related Costs		0		3	(6)		9
Commonwealth Edison Co [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19			19			15
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Commonwealth Edison Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		73	[3]		73	[3]		64
Commonwealth Edison Co [Member] | Recoverable Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		54			54			47
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		160			160			140
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	232			232			189
Business Combination, Integration Related Costs					11		11
Commonwealth Edison Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		43			43			46
Commonwealth Edison Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Commonwealth Edison Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Commonwealth Edison Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		74			74			67
Commonwealth Edison Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		267			267			255
Commonwealth Edison Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		58			58			52
Commonwealth Edison Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		244			244			247
Commonwealth Edison Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[5]	31			31			43
Business Combination, Integration Related Costs							7
Commonwealth Edison Co [Member] | Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		24			24			36
Commonwealth Edison Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Commonwealth Edison Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Commonwealth Edison Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Commonwealth Edison Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Commonwealth Edison Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
Commonwealth Edison Co [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
Commonwealth Edison Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10			10			10
Business Combination, Integration Related Costs					8
Commonwealth Edison Co [Member] | Advanced Metering Infrastructure Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19			19
Commonwealth Edison Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
Commonwealth Edison Co [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Commonwealth Edison Co [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Commonwealth Edison Co [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Commonwealth Edison Co [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Commonwealth Edison Co [Member] | Annual Reconciliations [Member]
Regulatory Assets [Line Items]
Regulatory Assets		178			178			142
Commonwealth Edison Co [Member] | Under-Recovered Electric Supply Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets								5
Commonwealth Edison Co [Member] | ElectricTransmissionCostsUnderRecovery [Member]
Regulatory Assets [Line Items]
Regulatory Assets		24			24			31
PECO Energy Co [Member]
Regulatory Assets [Line Items]
Current		37			37			34
Noncurrent		1,651			1,651			1,583
Regulatory Assets		1,688			1,688			1,617
Regulatory Liabilities		679			679			639
Business Combination, Integration Related Costs		1		1	3		4
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,555			1,555			1,473
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		53			53			63
PECO Energy Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1			1			1
PECO Energy Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Current		0			0
PECO Energy Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		22			22			22
PECO Energy Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		27			27			30
PECO Energy Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			1	[6]
PECO Energy Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0
PECO Energy Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1			1			1
PECO Energy Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PECO Energy Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9			9			13
PECO Energy Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PECO Energy Co [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		13			13			6
PECO Energy Co [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
PECO Energy Co [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7			7			7
Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Current		214			214			267
Noncurrent		508			508			514
Regulatory Assets		722			722			781
Regulatory Liabilities		172			172			222
Business Combination, Integration Related Costs		1		2	(3)		4
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		32			32			16
Baltimore Gas and Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3			3			12
Baltimore Gas and Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19			19			28
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		94	[3]		94	[3]		79
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Noncurrent		235			235			196
Regulatory Assets		235			235			196	[7]
Baltimore Gas and Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Baltimore Gas and Electric Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7			7			8
Baltimore Gas and Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Baltimore Gas and Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6			6			9
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11			11			19
Baltimore Gas and Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1			1			1
Baltimore Gas and Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Baltimore Gas and Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Baltimore Gas and Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[8]	25			25			40
Baltimore Gas and Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1			1			2
Baltimore Gas and Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		13			13			20
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		25			25			87
Baltimore Gas and Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		289			289			278
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[9]	10			10			6
Baltimore Gas and Electric Company [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets								3
Baltimore Gas and Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5			5			3
Business Combination, Integration Related Costs					6
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[10]	0			0			30
Baltimore Gas and Electric Company [Member] | Under-Recovered Electric Revenue Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			30
Baltimore Gas and Electric Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Baltimore Gas and Electric Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Baltimore Gas and Electric Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Baltimore Gas and Electric Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Baltimore Gas and Electric Company [Member] | Legacy AMI [Member]
Regulatory Assets [Line Items]
Regulatory Assets		55			55
Baltimore Gas and Electric Company [Member] | Recoverable Smart Meter Related Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		32			32
PEPCO Holdings Inc [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Current								305
Noncurrent								2,277
Regulatory Assets								2,582
Regulatory Liabilities								213
PEPCO Holdings Inc [Member] | Successor [Member]
Regulatory Assets [Line Items]
Current		650			650
Noncurrent		2,945			2,945
Regulatory Assets		3,595			3,595
Regulatory Liabilities		268			268
PEPCO Holdings Inc [Member] | Other Postretirement Benefits [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								910
PEPCO Holdings Inc [Member] | Other Postretirement Benefits [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[1]	0			0
PEPCO Holdings Inc [Member] | Deferred Income Tax Charge [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								214
PEPCO Holdings Inc [Member] | Deferred Income Tax Charge [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		251			251
PEPCO Holdings Inc [Member] | AMI Expenses [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								267
PEPCO Holdings Inc [Member] | AMI Expenses [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		256			256
PEPCO Holdings Inc [Member] | Under Recovered Distribution Service Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PEPCO Holdings Inc [Member] | Under Recovered Distribution Service Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0
PEPCO Holdings Inc [Member] | Loss on Reacquired Debt [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								36
PEPCO Holdings Inc [Member] | Loss on Reacquired Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[11]	82			82
PEPCO Holdings Inc [Member] | Fair Value Of Long Term Debt [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PEPCO Holdings Inc [Member] | Fair Value Of Long Term Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[2]	684			684
PEPCO Holdings Inc [Member] | Fair Value Of Supply Contract [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[12]	1,206			1,206
PEPCO Holdings Inc [Member] | Employee Severance [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PEPCO Holdings Inc [Member] | Employee Severance [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0
PEPCO Holdings Inc [Member] | Asset Retirement Obligation Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								1
PEPCO Holdings Inc [Member] | Asset Retirement Obligation Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1			1
PEPCO Holdings Inc [Member] | Environmental Restoration Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PEPCO Holdings Inc [Member] | Environmental Restoration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0
PEPCO Holdings Inc [Member] | Under Recovered Uncollectible Accounts Expense [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PEPCO Holdings Inc [Member] | Under Recovered Uncollectible Accounts Expense [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0
PEPCO Holdings Inc [Member] | Renewable Energy And Associated REC [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								6
PEPCO Holdings Inc [Member] | Renewable Energy And Associated REC [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2			2
PEPCO Holdings Inc [Member] | Under Recovered Energy And Transmission Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								33
PEPCO Holdings Inc [Member] | Under Recovered Energy And Transmission Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		18			18
PEPCO Holdings Inc [Member] | Deferred Storm Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								43
PEPCO Holdings Inc [Member] | Deferred Storm Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		38			38
PEPCO Holdings Inc [Member] | Electric Generation Related Regulatory Asset [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PEPCO Holdings Inc [Member] | Electric Generation Related Regulatory Asset [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0
PEPCO Holdings Inc [Member] | Rate Stabilization Deferral [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PEPCO Holdings Inc [Member] | Rate Stabilization Deferral [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0
PEPCO Holdings Inc [Member] | Energy Efficiency And Demand Response Programs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								401
PEPCO Holdings Inc [Member] | Energy Efficiency And Demand Response Programs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		352			352
PEPCO Holdings Inc [Member] | Merger Integration Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PEPCO Holdings Inc [Member] | Merger Integration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		13			13
PEPCO Holdings Inc [Member] | ConservativeVoltageReductionProgram [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PEPCO Holdings Inc [Member] | Regulatory Assets [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								32
PEPCO Holdings Inc [Member] | Regulatory Assets [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19			19
PEPCO Holdings Inc [Member] | Under Recovered Decoupling Revenue [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								14
PEPCO Holdings Inc [Member] | Under Recovered Decoupling Revenue [Member] | Successor [Member]
Regulatory Assets [Line Items]
Current		9			9
PEPCO Holdings Inc [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9			9
PEPCO Holdings Inc [Member] | Deferred Project Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
PEPCO Holdings Inc [Member] | Workers Compensation and Long-Term Disability [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								31
PEPCO Holdings Inc [Member] | Workers Compensation and Long-Term Disability [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		30			30
PEPCO Holdings Inc [Member] | Recoverable Vacation Pay [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								23
PEPCO Holdings Inc [Member] | Recoverable Vacation Pay [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		24			24
PEPCO Holdings Inc [Member] | Stranded Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								202
PEPCO Holdings Inc [Member] | Stranded Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		153			153
PEPCO Holdings Inc [Member] | AssetRemovalCosts [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets								369
PEPCO Holdings Inc [Member] | AssetRemovalCosts [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		448			448
Potomac Electric Power Company [Member]
Regulatory Assets [Line Items]
Current		122			122			140
Noncurrent		676			676			661
Regulatory Assets		798			798			801
Regulatory Liabilities		44			44			44
Potomac Electric Power Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		29			29			36
Potomac Electric Power Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets								5
Potomac Electric Power Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1			1
Potomac Electric Power Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	[1]		0	[1]		0
Potomac Electric Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		162	[3]		162	[3]		137
Potomac Electric Power Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		171	[7]		171	[7]		180
Potomac Electric Power Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Potomac Electric Power Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		18			18			19
Potomac Electric Power Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Potomac Electric Power Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Potomac Electric Power Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1			1			1
Potomac Electric Power Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Potomac Electric Power Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Potomac Electric Power Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Potomac Electric Power Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1			1			9	[13]
Potomac Electric Power Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		14			14			19
Potomac Electric Power Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Potomac Electric Power Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Potomac Electric Power Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		254			254			289
Potomac Electric Power Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10	[14]		10	[14]		0
Potomac Electric Power Company [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
Potomac Electric Power Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11			11			14
Business Combination, Integration Related Costs					10
Potomac Electric Power Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7			7			10
Potomac Electric Power Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Potomac Electric Power Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		30			30			31
Potomac Electric Power Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Potomac Electric Power Company [Member] | Abandonment costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets								4
Potomac Electric Power Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Potomac Electric Power Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		119			119			92
Potomac Electric Power Company [Member] | Legacy AMI [Member]
Regulatory Assets [Line Items]
Regulatory Assets		75			75
Potomac Electric Power Company [Member] | Recoverable Smart Meter Related Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		134			134
Potomac Electric Power Company [Member] | AMI Post Test Year [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3			3
Delmarva Power and Light Company [Member]
Regulatory Assets [Line Items]
Current		62			62			72
Noncurrent		297			297			299
Regulatory Assets		359			359			371
Regulatory Liabilities		146			146			160
Business Combination, Integration Related Costs		2		0	18		2
Delmarva Power and Light Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		20			20			18
Delmarva Power and Light Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1			1			7
Delmarva Power and Light Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7			7			1
Delmarva Power and Light Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	[1]		0	[1]		0
Delmarva Power and Light Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		38	[3]		38	[3]		36
Delmarva Power and Light Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		85	[7]		85	[7]		87
Delmarva Power and Light Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Delmarva Power and Light Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9			9			10
Delmarva Power and Light Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Delmarva Power and Light Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Delmarva Power and Light Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Delmarva Power and Light Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Delmarva Power and Light Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Delmarva Power and Light Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			1
Delmarva Power and Light Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[15]	8			8			11
Delmarva Power and Light Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5			5			6
Delmarva Power and Light Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Delmarva Power and Light Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Delmarva Power and Light Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		98			98			111
Delmarva Power and Light Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3	[16]		3	[16]		0
Delmarva Power and Light Company [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
Delmarva Power and Light Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4			4			9
Business Combination, Integration Related Costs					3
Delmarva Power and Light Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Current		2			2
Regulatory Assets								4
Delmarva Power and Light Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9			9			13
Delmarva Power and Light Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Delmarva Power and Light Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		14			14			14
Delmarva Power and Light Company [Member] | Abandonment costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets								3
Delmarva Power and Light Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Delmarva Power and Light Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		84			84			69
Delmarva Power and Light Company [Member] | Legacy AMI [Member]
Regulatory Assets [Line Items]
Regulatory Assets		14			14
Delmarva Power and Light Company [Member] | Recoverable Smart Meter Related Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		40			40
Atlantic City Electric Company [Member]
Regulatory Assets [Line Items]
Current		89			89			98
Noncurrent		412			412			414
Regulatory Assets		501			501			512
Regulatory Liabilities		36			36			25
Business Combination, Integration Related Costs		2		$ 0	17		$ 1
Atlantic City Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		18			18			15
Atlantic City Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4			4			2
Atlantic City Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5			5			11
Atlantic City Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	[1]		0	[1]		0
Atlantic City Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		51	[3]		51	[3]		41
Atlantic City Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6			6			7
Atlantic City Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0
Atlantic City Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2			2			5
Atlantic City Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[17]	9			9			13
Atlantic City Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19			19			18
Atlantic City Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0
Atlantic City Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			1
Atlantic City Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets								0
Atlantic City Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5			5			8
Atlantic City Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0
Atlantic City Electric Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10			10			9
Atlantic City Electric Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		153			153			202
Atlantic City Electric Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		$ 246			$ 246			$ 208

[1] As of September 30, 2016, the pension and other postretirement benefits regulatory asset at Exelon includes regulatory assets of $1,087 million established at the date of the PHI Merger related to unrecognized costs that are probable of regulatory recovery. The regulatory assets are amortized over periods from 3 to 15 years, depending on the underlying component. Pepco, DPL and ACE are currently recovering these costs through base rates. Pepco, DPL and ACE are not earning a return on the recovery of these costs in base rates.

[2] ncludes the unamortized regulatory assets recorded for the difference between carrying value and fair value of long-term debt of BGE as of the Constellation merger date and at Exelon and PHI for the difference between carrying value and fair value of long-term debt of Pepco, DPL and ACE as of the PHI Merger date.

[3] As of September 30, 2016, includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $19 million, $32 million, $29 million, $20 million and $18 million for ComEd, BGE, Pepco, DPL and ACE, respectively. As of December 31, 2015, includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $15 million, $16 million, $36 million, $18 million and $15 million for ComEd, BGE, Pepco, DPL and ACE, respectively.

[4] As of September 30, 2016, ComEd’s regulatory asset of $232 million was comprised of $178 million for the 2014 - 2016 annual reconciliations and $54 million related to significant one-time events including $24 million of deferred storm costs, $11 million of Constellation and PHI merger and integration related costs and $19 million of smart meter related costs. As of December 31, 2015, ComEd’s regulatory asset of $189 million was comprised of $142 million for the 2014 and 2015 annual reconciliations and $47 million related to significant one-time events, including $36 million of deferred storm costs and $11 million of Constellation merger and integration related costs. See Note 4— Merger, Acquisitions, and Dispositions of the Exelon 2015 Form 10-K for further information.

[5] As of September 30, 2016, ComEd’s regulatory asset of $31 million included $24 million associated with transmission costs recoverable through its FERC approved formula rate and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of September 30, 2016, ComEd’s regulatory liability of $72 million included $43 million related to over-recovered energy costs and $29 million associated with revenues received for renewable energy requirements. As of December 31, 2015, ComEd’s regulatory asset of $43 million included $5 million related to under-recovered energy costs, $31 million associated with transmission costs recoverable through its FERC approved formula rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2015, ComEd’s regulatory liability of $53 million included $29 million related to over-recovered energy costs and $24 million associated with revenues received for renewable energy requirements.

[6] As of September 30, 2016, PECO's regulatory liability of $59 million included $30 million related to over-recovered costs under the DSP program, $13 million related to the over-recovered natural gas costs under the PGC, $10 million related to over-recovered non-bypassable transmission service charges and $6 million related to over-recovered electric transmission costs. As of December 31, 2015, PECO's regulatory asset of $1 million related to under-recovered non-bypassable transmission service charges. As of December 31, 2015, PECO's regulatory liability of $60 million included $35 million related to over-recovered costs under the DSP program, $22 million related to the over-recovered natural gas costs under the PGC and $3 million related to the over-recovered electric transmission costs.

[7] $134 million for Pepco and $40 million for DPL, of which $75 million for Pepco and $14 million for DPL relates to retired legacy meters which are not earning a return

[8] As of September 30, 2016, BGE's regulatory asset of $25 million included $3 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $19 million related to under-recovered electric energy costs, $3 million of abandonment costs to be recovered upon FERC approval, and $1 million related to under-recovered natural gas costs. As of December 31, 2015, BGE’s regulatory asset of $40 million included $12 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $28 million related to under-recovered electric energy costs. As of December 31, 2015, BGE’s regulatory liability of $18 million related to $14 million of over-recovered transmission costs and $5 million of over-recovered natural gas costs, offset by $1 million of abandonment costs to be recovered upon FERC approval.

[9] As of September 30, 2016, BGE's regulatory asset of $10 million included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order.

[10] Represents the electric and natural gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of September 30, 2016, BGE had a regulatory liability of $5 million related to over-recovered natural gas revenue decoupling and $0 million related to over-recovered electric revenue decoupling. As of December 31, 2015, BGE had a regulatory asset of $30 million related to under-recovered electric revenue decoupling and a regulatory liability of $1 million related to over-recovered natural gas revenue decoupling.

[11] Includes at Exelon and PHI the regulatory asset recorded at PHI for debt costs that are recoverable through the ratemaking process at Pepco, DPL, and ACE which were eliminated at Exelon and PHI as part of acquisition accounting.

[12] Represents the regulatory asset recorded at Exelon and PHI offsetting the fair value adjustments related to Pepco's, DPL's and ACE's electricity and natural gas energy supply contracts recorded at PHI as of the PHI Merger date. Pepco, DPL and ACE are allowed full recovery of the costs of these contracts through their respective rate making processes.

[13] As of September 30, 2016, Pepco's regulatory liability of $17 million included $9 million of over-recovered transmission costs and $8 million of over-recovered electric energy costs. As of December 31, 2015, Pepco's regulatory asset of $9 million included $5 million of transmission costs recoverable through its FERC approved formula rate and $4 million of recoverable abandonment costs. As of December 31, 2015, Pepco's regulatory liability of $16 million included $14 million of over-recovered transmission costs and $2 million of over-recovered electric energy costs.

[14] epresents previously incurred PHI acquisition costs expected to be recovered in distribution rates

[15] As of September 30, 2016, DPL's regulatory asset of $8 million included $1 million of transmission costs recoverable through its FERC approved formula rate and $7 million of under-recovered electric energy costs. As of September 30, 2016, DPL's regulatory liability of $11 million included $6 million of over-recovered electric energy costs and $5 million of over-recovered transmission costs. As of December 31, 2015, DPL's regulatory asset of $11 million included $7 million of transmission costs recoverable through its FERC approved formula rate, $3 million of recoverable abandonment costs, and $1 million of under-recovered electric energy costs. As of December 31, 2015, DPL's regulatory liability of $19 million included $4 million related to the over-recovered natural gas costs under the GCR mechanism, $4 million of over-recovered electric energy costs, and $11 million of over-recovered transmission costs.

[16] .

[17] As of September 30, 2016, ACE's regulatory asset of $9 million included $4 million of transmission costs recoverable through its FERC approved formula rate and $5 million of under-recovered electric energy costs. As of September 30, 2016, ACE's regulatory liability of $12 million included $7 million of over-recovered transmission costs and $5 million of over-recovered electric energy costs. As of December 31, 2015, ACE's regulatory asset of $13 million included $2 million of transmission costs recoverable through its FERC approved formula rate and $11 million of under-recovered electric energy costs. As of December 31, 2015, ACE's regulatory liability of $8 million related to over-recovered transmission costs.