Regulatory Matters Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions			3 Months Ended								12 Months Ended
		Mar. 31, 2016	Mar. 31, 2017		Dec. 31, 2016		Jun. 30, 2016	Mar. 31, 2016		Mar. 23, 2016	Dec. 31, 2016
Regulatory Assets [Line Items]
Current			$ 1,330.0		$ 1,342.0						$ 1,342.0
Noncurrent			10,051.0		10,046.0						10,046.0
Regulatory Assets			11,381.0		11,388.0						11,388.0
Regulatory Liabilities			4,939.0		4,789.0						4,789.0
Business Combination, Integration Related Costs	[1],[2]		9.0					$ 102.0
Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4,152.0	[3]	4,162.0						4,162.0
Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			2,055.0		2,016.0						2,016.0
AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			689.0		701.0						701.0
Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			211.0		188.0						188.0
Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			122.0		124.0						124.0
Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			797.0		812.0	[4]					812.0	[4]
Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Current			1,021.0
Regulatory Assets					1,085.0						1,085.0
Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4.0		5.0						5.0
Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			116.0		111.0						111.0
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			296.0		305.0						305.0
Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			63.0		56.0						56.0
Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			285.0		260.0						260.0
Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			71.0		89.0						89.0
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			39.0		36.0						36.0
Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			8.0		10.0						10.0
Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets					7.0						7.0
Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			596.0		621.0						621.0
Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			32.0		25.0						25.0
Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			46.0		49.0						49.0
Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			76.0		27.0						27.0
Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7.0		8.0						8.0
Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			33.0		34.0						34.0
Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			42.0		31.0						31.0
Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			123.0		138.0						138.0
CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets			11.0		11.0						11.0
AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			486.0		477.0						477.0
Under funded Benefit Post Retirement Obligation [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[3]		1,087.0
Commonwealth Edison Co [Member]
Regulatory Assets [Line Items]
Current			183.0		190.0						190.0
Noncurrent			1,032.0		977.0						977.0
Regulatory Assets			1,215.0		1,167.0						1,167.0
Public Utilities, Interim Rate Increase (Decrease), Amount											(8.0)
Regulatory Liabilities			3,803.0		3,698.0						3,698.0
Business Combination, Integration Related Costs	[2]		0.0					(8.0)	[5]
Commonwealth Edison Co [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			22.0		22.0						22.0
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Commonwealth Edison Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			76.0	[6]	75.0						75.0
Commonwealth Edison Co [Member] | Recoverable Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			53.0		54.0						54.0
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			165.0		164.0						164.0
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[7]		211.0		188.0						188.0
Business Combination, Integration Related Costs			10.0								11.0
Commonwealth Edison Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			41.0		42.0						42.0
Commonwealth Edison Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Commonwealth Edison Co [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0.0						0.0
Commonwealth Edison Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Commonwealth Edison Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			82.0		76.0						76.0
Commonwealth Edison Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			271.0		278.0						278.0
Commonwealth Edison Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			63.0		56.0						56.0
Commonwealth Edison Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			282.0		258.0						258.0
Commonwealth Edison Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[8]		18.0		23.0						23.0
Business Combination, Integration Related Costs			8.0		8.0
Commonwealth Edison Co [Member] | Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			17.0		20.0						20.0
Commonwealth Edison Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Commonwealth Edison Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Commonwealth Edison Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0.0						0.0
Commonwealth Edison Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Commonwealth Edison Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0.0						0.0
Commonwealth Edison Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			6.0		7.0						7.0
Business Combination, Integration Related Costs								9.0
Commonwealth Edison Co [Member] | Advanced Metering Infrastructure Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			26.0		23.0						23.0
Commonwealth Edison Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0.0						0.0
Commonwealth Edison Co [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Commonwealth Edison Co [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Commonwealth Edison Co [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Commonwealth Edison Co [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Commonwealth Edison Co [Member] | Annual Reconciliations [Member]
Regulatory Assets [Line Items]
Regulatory Assets			158.0		134.0						134.0
Commonwealth Edison Co [Member] | ElectricTransmissionCostsUnderRecovery [Member]
Regulatory Assets [Line Items]
Regulatory Assets			10.0		15.0						15.0
PECO Energy Co [Member]
Regulatory Assets [Line Items]
Current			40.0		29.0						29.0
Noncurrent			1,708.0		1,681.0						1,681.0
Regulatory Assets			1,748.0		1,710.0						1,710.0
Regulatory Liabilities			691.0		644.0						644.0
Business Combination, Integration Related Costs	[2]		1.0					2.0
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
PECO Energy Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1,617.0		1,583.0						1,583.0
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			46.0		49.0						49.0
PECO Energy Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
PECO Energy Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1.0		1.0						1.0
PECO Energy Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
PECO Energy Co [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Current			0.0
Regulatory Assets					0.0						0.0
PECO Energy Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
PECO Energy Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			22.0		23.0						23.0
PECO Energy Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			25.0		26.0						26.0
PECO Energy Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
PECO Energy Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
PECO Energy Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
PECO Energy Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						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						0.0
PECO Energy Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1.0		1.0						1.0
PECO Energy Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
PECO Energy Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			8.0		9.0						9.0
PECO Energy Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0.0						0.0
PECO Energy Co [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
PECO Energy Co [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
PECO Energy Co [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			17.0		7.0						7.0
PECO Energy Co [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
PECO Energy Co [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets			11.0		11.0						11.0
Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Current			191.0		208.0						208.0
Noncurrent			499.0		504.0						504.0
Regulatory Assets			690.0		712.0						712.0
Regulatory Liabilities			161.0		160.0						160.0
Business Combination, Integration Related Costs	[2]		2.0					2.0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			39.0		38.0						38.0
Baltimore Gas and Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets			3.0		4.0						4.0
Baltimore Gas and Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			13.0		28.0						28.0
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			101.0	[6]	98.0						98.0
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Noncurrent			225.0		230.0						230.0
Regulatory Assets			225.0		230.0	[9]					230.0	[9]
Baltimore Gas and Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Baltimore Gas and Electric Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7.0		7.0						7.0
Baltimore Gas and Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Baltimore Gas and Electric Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0.0						0.0
Baltimore Gas and Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4.0		5.0						5.0
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			12.0		12.0						12.0
Baltimore Gas and Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		1.0						1.0
Baltimore Gas and Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Baltimore Gas and Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Baltimore Gas and Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[10]		19.0		38.0						38.0
Baltimore Gas and Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1.0		1.0						1.0
Baltimore Gas and Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			8.0		10.0						10.0
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets					7.0						7.0
Baltimore Gas and Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			269.0		285.0						285.0
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[11]		8.0		10.0		$ 6.0				10.0
Baltimore Gas and Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			5.0		5.0						5.0
Baltimore Gas and Electric Company [Member] | Advanced Metering Infrastructure Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			140.0
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[12]		31.0		3.0						3.0
Baltimore Gas and Electric Company [Member] | UnderRecoveredNaturalGasDecouplingRevenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			6.0		2.0						2.0
Baltimore Gas and Electric Company [Member] | Under-Recovered Electric Revenue Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets			25.0
Baltimore Gas and Electric Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Baltimore Gas and Electric Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Baltimore Gas and Electric Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Baltimore Gas and Electric Company [Member] | Abandonment costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets					3.0						3.0
Baltimore Gas and Electric Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Baltimore Gas and Electric Company [Member] | Legacy AMI [Member]
Regulatory Assets [Line Items]
Regulatory Assets			53.0				56.0
Baltimore Gas and Electric Company [Member] | Recoverable Smart Meter Related Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			32.0
Pepco Holdings LLC [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs	[2]		1.0					27.0
Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs										$ 29.0
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Assets [Line Items]
Current			653.0		653.0						653.0
Noncurrent			2,791.0		2,851.0						2,851.0
Regulatory Assets			3,444.0		3,504.0						3,504.0
Regulatory Liabilities			236.0		237.0						237.0
Business Combination, Integration Related Costs		$ 56.0	(5.0)
Pepco Holdings LLC [Member] | Other Postretirement Benefits [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0	[3]	0.0						0.0
Pepco Holdings LLC [Member] | Deferred Income Tax Charge [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			261.0		260.0						260.0
Pepco Holdings LLC [Member] | AMI Expenses [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			253.0		258.0						258.0
Pepco Holdings LLC [Member] | Under Recovered Distribution Service Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Pepco Holdings LLC [Member] | Loss on Reacquired Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			80.0	[13]	81.0						81.0
Pepco Holdings LLC [Member] | Fair Value Of Long Term Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			658.0	[4]	671.0						671.0
Pepco Holdings LLC [Member] | Fair Value Of Supply Contract [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1,021.0	[14]	1,085.0						1,085.0
Pepco Holdings LLC [Member] | Employee Severance [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Pepco Holdings LLC [Member] | Asset Retirement Obligation Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Pepco Holdings LLC [Member] | Environmental Restoration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Pepco Holdings LLC [Member] | Under Recovered Uncollectible Accounts Expense [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Pepco Holdings LLC [Member] | Renewable Energy And Associated REC [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			3.0		2.0						2.0
Pepco Holdings LLC [Member] | Under Recovered Energy And Transmission Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			34.0		28.0						28.0
Pepco Holdings LLC [Member] | Deferred Storm Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			38.0		35.0						35.0
Pepco Holdings LLC [Member] | Electric Generation Related Regulatory Asset [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Pepco Holdings LLC [Member] | Rate Stabilization Deferral [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0.0						0.0
Pepco Holdings LLC [Member] | Energy Efficiency And Demand Response Programs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			326.0		335.0						335.0
Pepco Holdings LLC [Member] | Merger Integration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			24.0		15.0						15.0
Pepco Holdings LLC [Member] | Regulatory Assets [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			27.0		29.0						29.0
Pepco Holdings LLC [Member] | Under Recovered Decoupling Revenue [Member] | Successor [Member]
Regulatory Assets [Line Items]
Current			45.0
Regulatory Assets					24.0						24.0
Pepco Holdings LLC [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7.0
Pepco Holdings LLC [Member] | Deferred Project Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					8.0						8.0
Pepco Holdings LLC [Member] | Workers Compensation and Long-Term Disability [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			33.0		34.0						34.0
Pepco Holdings LLC [Member] | Recoverable Vacation Pay [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			25.0		24.0						24.0
Pepco Holdings LLC [Member] | Stranded Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			123.0		138.0						138.0
Pepco Holdings LLC [Member] | AssetRemovalCosts [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			486.0		477.0						477.0
Potomac Electric Power Company [Member]
Regulatory Assets [Line Items]
Current			173.0		162.0						162.0
Noncurrent			679.0		690.0						690.0
Regulatory Assets			852.0		852.0						852.0
Regulatory Liabilities			29.0		31.0						31.0
Potomac Electric Power Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			31.0		31.0						31.0
Potomac Electric Power Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets			2.0
Potomac Electric Power Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4.0
Potomac Electric Power Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0	[3]	0.0						0.0
Potomac Electric Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			169.0	[6]	171.0						171.0
Potomac Electric Power Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			170.0	[9]	174.0						174.0
Potomac Electric Power Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Potomac Electric Power Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			17.0		17.0						17.0
Potomac Electric Power Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Potomac Electric Power Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0.0						0.0
Potomac Electric Power Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Potomac Electric Power Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Potomac Electric Power Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Potomac Electric Power Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Potomac Electric Power Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Potomac Electric Power Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			6.0		6.0						6.0
Potomac Electric Power Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			12.0		12.0						12.0
Potomac Electric Power Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Potomac Electric Power Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0.0						0.0
Potomac Electric Power Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			241.0		250.0						250.0
Potomac Electric Power Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			11.0	[15]	11.0						11.0
Potomac Electric Power Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			21.0		22.0						22.0
Potomac Electric Power Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			36.0		21.0						21.0
Potomac Electric Power Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Potomac Electric Power Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			33.0		34.0						34.0
Potomac Electric Power Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Potomac Electric Power Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Potomac Electric Power Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			136.0		134.0						134.0
Delmarva Power and Light Company [Member]
Regulatory Assets [Line Items]
Current			66.0		59.0						59.0
Noncurrent			301.0		289.0						289.0
Regulatory Assets			367.0		348.0						348.0
Public Utilities, Interim Rate Increase (Decrease), Amount							$ 2.5
Regulatory Liabilities			142.0		140.0						140.0
Business Combination, Integration Related Costs	[2]		(7.0)	[16]				16.0
Delmarva Power and Light Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			21.0		20.0						20.0
Delmarva Power and Light Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets					1.0						1.0
Delmarva Power and Light Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			5.0		4.0						4.0
Delmarva Power and Light Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0	[3]	0.0						0.0
Delmarva Power and Light Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			40.0	[6]	38.0						38.0
Delmarva Power and Light Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			83.0	[9]	84.0						84.0
Delmarva Power and Light Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Delmarva Power and Light Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			9.0		9.0						9.0
Delmarva Power and Light Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Delmarva Power and Light Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0.0						0.0
Delmarva Power and Light Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Delmarva Power and Light Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Delmarva Power and Light Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Delmarva Power and Light Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Delmarva Power and Light Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1.0		0.0						0.0
Delmarva Power and Light Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[17]		5.0		5.0						5.0
Delmarva Power and Light Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7.0		5.0						5.0
Delmarva Power and Light Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Delmarva Power and Light Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0.0						0.0
Delmarva Power and Light Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			84.0		85.0						85.0
Delmarva Power and Light Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[15]		13.0		4.0						4.0
Delmarva Power and Light Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4.0		5.0						5.0
Business Combination, Integration Related Costs			8.0
Delmarva Power and Light Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Current			9.0
Regulatory Assets					3.0						3.0
Delmarva Power and Light Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7.0		8.0						8.0
Delmarva Power and Light Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Delmarva Power and Light Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			15.0		14.0						14.0
Delmarva Power and Light Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Delmarva Power and Light Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			90.0		88.0						88.0
Atlantic City Electric Company [Member]
Regulatory Assets [Line Items]
Current			94.0		96.0						96.0
Noncurrent			407.0		405.0						405.0
Regulatory Assets			501.0		501.0						501.0
Regulatory Liabilities			25.0		25.0						25.0
Business Combination, Integration Related Costs	[2]		1.0					$ 13.0
Atlantic City Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			20.0		19.0						19.0
Atlantic City Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets			10.0		6.0						6.0
Atlantic City Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			13.0		11.0						11.0
Atlantic City Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0	[3]	0.0						0.0
Atlantic City Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			52.0	[6]	51.0						51.0
Atlantic City Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			6.0		6.0						6.0
Atlantic City Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			2.0		2.0						2.0
Atlantic City Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[18]		23.0		17.0						17.0
Atlantic City Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			19.0		18.0						18.0
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						0.0
Atlantic City Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1.0		0.0						0.0
Atlantic City Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4.0		4.0						4.0
Atlantic City Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0.0		0.0						0.0
Atlantic City Electric Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			10.0		10.0						10.0
Atlantic City Electric Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			123.0		138.0						138.0
Atlantic City Electric Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			$ 261.0		$ 255.0						$ 255.0

[1] Reflects costs (benefits) recorded at Exelon related to financing, including mark-to-market activity on forward-starting interest rate swaps.

[2] The costs incurred are classified primarily within Operating and maintenance expense in the Registrants’ respective Consolidated Statements of Operations and Comprehensive Income, with the exception of the financing costs, which are included within Interest expense. Costs do not include merger commitments discussed above.

[3] As of March 31, 2017 and December 31, 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.

[4] .

[5] For the three months ended March 31, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $9 million, incurred at ComEd that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.

[6] As of March 31, 2017, includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $22 million, $39 million, $31 million, $21 million and $20 million for ComEd, BGE, Pepco, DPL and ACE, respectively. As of December 31, 2016, includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $22 million, $38 million, $31 million, $20 million and $19 million for ComEd, BGE, Pepco, DPL and ACE, respectively.

[7] As of March 31, 2017, ComEd’s regulatory asset of $211 million was comprised of $158 million for the 2015 - 2017 annual reconciliations and $53 million related to significant one-time events including $17 million of deferred storm costs, $10 million of Constellation and PHI merger and integration related costs and $26 million of smart meter related costs. As of December 31, 2016, ComEd’s regulatory asset of $188 million was comprised of $134 million for the 2015 and 2016 annual reconciliations and $54 million related to significant one-time events, including $20 million of deferred storm costs and $11 million of Constellation and PHI merger and integration related costs, and $23 million of smart meter related costs. ComEd's 2015 annual reconciliation regulatory asset included a reduction of $8 million related to a ComEd-proposed refund to customers for the impact of changing its OSHA recordable rate for 2014 and 2015. See Note 4— Merger, Acquisitions, and Dispositions of the Exelon 2016 Form 10-K for further information.

[8] As of March 31, 2017, ComEd’s regulatory asset of $18 million included $10 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of March 31, 2017, ComEd’s regulatory liability of $38 million included $6 million related to over-recovered energy costs and $32 million associated with revenues received for renewable energy requirements. As of December 31, 2016, ComEd’s regulatory asset of $23 million included $15 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2016, ComEd’s regulatory liability of $60 million included $30 million related to over-recovered energy costs and $30 million associated with revenues received for renewable energy requirements.

[9] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246OUQ2REY5QzBDOTYwNUNBMEEyNzM0RkVGRjBENjIxNzEM}

[10] As of March 31, 2017, PECO's regulatory liability of $66 million included $41 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 $2 million related to over-recovered electric transmission costs. As of December 31, 2016, PECO's regulatory liability of $56 million included $34 million related to over-recovered costs under the DSP program, $10 million related to over-recovered non-bypassable transmission service charges, $8 million related to the over-recovered natural gas costs under the PGC and $4 million related to the over-recovered electric transmission costs.

[11] As of March 31, 2017, ACE's regulatory asset of $23 million included $10 million of transmission costs recoverable through its FERC approved formula rate and $13 million of under-recovered electric energy costs. As of March 31, 2017, ACE's regulatory liability of $8 million included $2 million of over-recovered transmission costs and $6 million of over-recovered electric energy costs. As of December 31, 2016, ACE's regulatory asset of $17 million included $6 million of transmission costs recoverable through its FERC approved formula rate and $11 million of under-recovered electric energy costs. As of December 31, 2016, ACE's regulatory liability of $5 million included $4 million of over-recovered transmission costs and $1 million of over-recovered electric energy costs.

[12] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246QTMwMjk0OTRCOENBNTU2NkI1MzcxQjk3NDgwNEUyMzMM}

[13] .

[14] .

[15] As of March 31, 2017, BGE's regulatory asset of $8 million included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order.

[16] For the three months ended March 31, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million, incurred at DPL that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.

[17] As of March 31, 2017, Pepco's regulatory asset of $6 million included $2 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of March 31, 2017, Pepco's regulatory liability of $7 million included $2 million of over-recovered transmission costs and $5 million of over-recovered electric energy costs. As of December 31, 2016, Pepco's regulatory asset of $6 million related to under-recovered electric energy costs. As of December 31, 2016, Pepco's regulatory liability of $8 million included $5 million of over-recovered transmission costs and $3 million of over-recovered electric energy costs.

[18] As of March 31, 2017, DPL's regulatory asset of $5 million related to under-recovered electric energy costs. As of March 31, 2017, DPL's regulatory liability of $12 million included $9 million of over-recovered electric energy costs, $1 million of over-recovered transmission costs, and $2 million of over-recovered gas cost. As of December 31, 2016, DPL's regulatory asset of $5 million included $1 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of December 31, 2016, DPL's regulatory liability of $5 million included $2 million of over-recovered electric energy costs and $3 million of over-recovered transmission costs.