Debt and Credit Agreements - Summary of Outstanding Long-term Debt (Details) - USD ($) $ in Millions		1 Months Ended	9 Months Ended	12 Months Ended
		Feb. 08, 2019	Sep. 30, 2018	Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2014
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				$ 1,349
Long-term Debt, Gross				34,911		$ 33,657
Unamortized debt discount and premium, net				(66)		(57)
Unamortized Debt Issuance Expense				(216)		(201)
Fair value adjustment				795		865
Long-term debt due within one year				(1,349)	[1]	(2,088)
Long-term debt				34,075		32,176
Long-term debt to financing trusts				390		389
2020				3,528
2021				1,511
Repayments of Long-term Debt				1,786		2,490	$ 1,936
ComEd Financing III Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts				206		205
PECO Trust III Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts				81		81
PECO Trust IV Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts				103		103
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[2]			$ 16,496		15,197
Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[2]			1.70%
Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[2]			7.90%
Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 11,285		11,285
Senior Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.45%
Senior Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				7.60%
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 2,900		2,600
Unsecured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.40%
Unsecured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				6.35%
Pollution Control Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 435		435
Pollution Control Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.50%
Pollution Control Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.70%
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 39		82
Notes Payable to Banks [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				3.15%
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[3],[4]			$ 188		405
Unamortized Debt Issuance Expense				$ 0		$ (1)
Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3],[4]			2.85%
Notes Payable, Other Payables [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3],[4]			8.88%
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						3.497%		2.50%
Long-term Debt, Gross				$ 1,150		$ 1,150
Junior Subordinated Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				3.50%
Software License Arrangement [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 73		79
Software License Arrangement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				3.95%
Tax-exempt Money Market Funds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 112		112
Tax-exempt Money Market Funds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				1.74%
Tax-exempt Money Market Funds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				5.40%
Medium-term Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 22		26
Medium-term Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				7.61%
Medium-term Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				7.72%
Transition Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 59		90
Transition Bonds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				5.55%
Loans Payable [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 50		0
Loans Payable [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.00%
Non Recourse Fixed Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 1,253		1,331
Non Recourse Fixed Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.29%
Non Recourse Fixed Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				6.00%
Non Recourse Variable Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[5]			$ 849		865
Non Recourse Variable Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[5]			5.81%
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations, noncurrent				$ 36		53
Due in 2019				21
Due in 2020				5
Due in 2021				1
Due in 2022				1
Due in 2023				0
Thereafter				8
Long-term Debt [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts				390		390
Long-term Debt [Member] | ComEd Financing III Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	[6]			$ 206		206
Long-term Debt [Member] | ComEd Financing III Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[6]			6.35%
Long-term Debt [Member] | PECO Trust III Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	[6]			$ 81		81
Long-term Debt [Member] | PECO Trust III Affiliate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[6]			7.38%
Long-term Debt [Member] | PECO Trust III Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[6]			7.50%
Long-term Debt [Member] | PECO Trust IV Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	[6]			$ 103		103
Long-term Debt [Member] | PECO Trust IV Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[6]			5.75%
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				$ 906
Long-term Debt, Gross				8,759		8,955
Unamortized debt discount and premium, net				(6)		(8)
Unamortized Debt Issuance Expense				(51)		(60)
Fair value adjustment				91		103
Long-term debt due within one year				(906)		(346)
Long-term debt				6,989		7,734
Debt and Capital Lease Obligations				7,887		8,644
2020				2,108
2021				1
Repayments of Long-term Debt				141		1,261	202
Exelon Generation Co L L C [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 6,019		6,019
Exelon Generation Co L L C [Member] | Senior Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.95%
Exelon Generation Co L L C [Member] | Senior Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				7.60%
Exelon Generation Co L L C [Member] | Pollution Control Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 435		435
Exelon Generation Co L L C [Member] | Pollution Control Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.50%
Exelon Generation Co L L C [Member] | Pollution Control Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.70%
Exelon Generation Co L L C [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 39		82
Exelon Generation Co L L C [Member] | Notes Payable to Banks [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				3.15%
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[7],[8]			$ 164		223
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[7],[8]			2.85%
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[7],[8]			7.83%
Exelon Generation Co L L C [Member] | Non Recourse Fixed Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 1,253		1,331
Exelon Generation Co L L C [Member] | Non Recourse Fixed Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.29%
Exelon Generation Co L L C [Member] | Non Recourse Fixed Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				6.00%
Exelon Generation Co L L C [Member] | Non Recourse Variable Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[9]			$ 849		865
Exelon Generation Co L L C [Member] | Non Recourse Variable Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[9]			5.81%
Exelon Generation Co L L C [Member] | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations, noncurrent				$ 14		18
Due in 2019				7
Due in 2020				5
Due in 2021				1
Due in 2022				1
Due in 2023				0
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				300
Long-term Debt, Gross				8,187		7,676
Unamortized debt discount and premium, net				(23)		(23)
Unamortized Debt Issuance Expense				(63)		(52)
Long-term debt due within one year				(300)	[10]	(840)
Long-term debt				7,801		6,761
Long-term debt to financing trusts				205		205
Debt and Capital Lease Obligations				7,801		6,761
2020				500
2021				350
Repayments of Long-term Debt				840		425	665
Commonwealth Edison Co [Member] | ComEd Financing III Affiliate [Member]
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense				(1)		(1)
Long-term debt to financing trusts				205		205
Commonwealth Edison Co [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[11]			$ 8,179		7,529
Commonwealth Edison Co [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[11]			2.15%
Commonwealth Edison Co [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[11]			6.45%
Commonwealth Edison Co [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[12]			$ 8		147
Commonwealth Edison Co [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[12]
Commonwealth Edison Co [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[12]			7.49%
Commonwealth Edison Co [Member] | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations, noncurrent				$ 8
Thereafter				1
Commonwealth Edison Co [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts				206		206
Commonwealth Edison Co [Member] | Long-term Debt [Member] | ComEd Financing III Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	[13]			$ 206		206
Commonwealth Edison Co [Member] | Long-term Debt [Member] | ComEd Financing III Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[13]			6.35%
PECO Energy Co [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				$ 0
Long-term Debt, Gross				3,125		2,925
Unamortized debt discount and premium, net				(18)		(5)
Unamortized Debt Issuance Expense				(23)		(17)
Long-term debt				3,084		2,403
Long-term debt to financing trusts	[14]			184		184
Long-term debt due within one year				0		(500)
Debt and Capital Lease Obligations				3,084		2,403
2020				0
2021				300
Repayments of Long-term Debt				500		0	300
PECO Energy Co [Member] | PECO Trust III Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts				81		81
PECO Energy Co [Member] | PECO Trust IV Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts				103		103
PECO Energy Co [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[15]			$ 3,075		2,925
PECO Energy Co [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[15]			1.70%
PECO Energy Co [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[15]			5.95%
PECO Energy Co [Member] | Loans Payable [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 50		0
PECO Energy Co [Member] | Loans Payable [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.00%
PECO Energy Co [Member] | Long-term Debt [Member] | PECO Trust III Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	[14]			$ 81		81
PECO Energy Co [Member] | Long-term Debt [Member] | PECO Trust III Affiliate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[14]			7.38%
PECO Energy Co [Member] | Long-term Debt [Member] | PECO Trust III Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[14]			7.50%
PECO Energy Co [Member] | Long-term Debt [Member] | PECO Trust IV Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	[14]			$ 103		103
PECO Energy Co [Member] | Long-term Debt [Member] | PECO Trust IV Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[14]			5.75%
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				$ 0
Long-term Debt, Gross				2,900		2,600
Unamortized debt discount and premium, net				(6)		(6)
Unamortized Debt Issuance Expense				(18)		(17)
Long-term debt				2,876		2,577
Long-term debt				2,876		2,577
2020				0
2021				300
Repayments of Long-term Debt				0		41	379
Baltimore Gas and Electric Company [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 2,900		2,600
Baltimore Gas and Electric Company [Member] | Senior Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.40%
Baltimore Gas and Electric Company [Member] | Senior Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				6.35%
Pepco Holdings LLC [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				$ 125
Long-term Debt, Gross				5,636		5,189
Unamortized debt discount and premium, net				4		5
Unamortized Debt Issuance Expense				(14)		(6)
Fair value adjustment				633		686
Long-term debt				6,134		5,478
Long-term debt due within one year				(125)		(396)
Long-term debt				6,134		5,478
2020				20
2021				261
Repayments of Long-term Debt				299		169
Pepco Holdings LLC [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[16]			$ 5,242		4,743
Pepco Holdings LLC [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[16]			1.81%
Pepco Holdings LLC [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[16]			7.90%
Pepco Holdings LLC [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 185		185
Pepco Holdings LLC [Member] | Unsecured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				7.45%
Pepco Holdings LLC [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[17]			$ 16		33
Pepco Holdings LLC [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[17]			7.28%
Pepco Holdings LLC [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[17]			8.88%
Pepco Holdings LLC [Member] | Tax-exempt Money Market Funds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 112		112
Pepco Holdings LLC [Member] | Tax-exempt Money Market Funds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				1.74%
Pepco Holdings LLC [Member] | Tax-exempt Money Market Funds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				5.40%
Pepco Holdings LLC [Member] | Medium-term Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 22		26
Pepco Holdings LLC [Member] | Medium-term Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				7.61%
Pepco Holdings LLC [Member] | Medium-term Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				7.72%
Pepco Holdings LLC [Member] | Transition Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[18]			$ 59		90
Pepco Holdings LLC [Member] | Transition Bonds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[18]
Pepco Holdings LLC [Member] | Transition Bonds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[18]			5.55%
Pepco Holdings LLC [Member] | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations, current				$ 14
Capital lease obligations, noncurrent						27
Potomac Electric Power Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				15
Long-term Debt, Gross				2,751		2,570
Unamortized debt discount and premium, net				2		2
Unamortized Debt Issuance Expense				(34)		(32)
Long-term debt				2,704		2,521
Long-term debt due within one year				(15)		(19)
Long-term debt				2,704		2,521
Due in 2019				14
2020				0
2021				1
Repayments of Long-term Debt				14		13	11
Potomac Electric Power Company [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[19]			$ 2,735		2,535
Potomac Electric Power Company [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[19]			3.05%
Potomac Electric Power Company [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[19]			7.90%
Potomac Electric Power Company [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[20]			$ 16		35
Potomac Electric Power Company [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[20]			7.28%
Potomac Electric Power Company [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[20]			8.88%
Delmarva Power & Light Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				$ 91
Long-term Debt, Gross				1,504		1,309
Unamortized debt discount and premium, net				2		2
Unamortized Debt Issuance Expense				(12)		(11)
Long-term debt due within one year				(79)		(79)
Long-term debt				1,403		1,217
Long-term debt due within one year				(91)		(83)
Long-term debt				1,403		1,217
2020				0
2021				0
Repayments of Long-term Debt				4		40	100
Delmarva Power & Light Company [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[21]			$ 1,370		1,171
Delmarva Power & Light Company [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[21]			1.81%
Delmarva Power & Light Company [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[21]			4.27%
Delmarva Power & Light Company [Member] | Tax-exempt Money Market Funds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 112		112
Delmarva Power & Light Company [Member] | Tax-exempt Money Market Funds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				1.74%
Delmarva Power & Light Company [Member] | Tax-exempt Money Market Funds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				5.40%
Delmarva Power & Light Company [Member] | Medium-term Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 22		26
Delmarva Power & Light Company [Member] | Medium-term Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				7.61%
Delmarva Power & Light Company [Member] | Medium-term Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				7.72%
Atlantic City Electric Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				$ 18
Long-term Debt, Gross				1,196		1,127
Unamortized debt discount and premium, net				(1)		(1)
Unamortized Debt Issuance Expense				(7)		(5)
Long-term debt				1,170		840
Long-term debt due within one year				(18)		(281)
Long-term debt				1,170		840
2020				20
2021				260
Repayments of Long-term Debt				281		35	$ 48
Atlantic City Electric Company [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[22]			$ 1,137		1,037
Atlantic City Electric Company [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[22]			3.38%
Atlantic City Electric Company [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[22]			6.80%
Atlantic City Electric Company [Member] | Transition Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months				$ 18
Long-term Debt, Gross	[23]			59		$ 90
2020				20
2021				$ 21
Atlantic City Electric Company [Member] | Transition Bonds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[23]			5.55%
AGEPFNotesNov2017 [Member] | AGE Biomass project [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt			$ 228
Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of Debt		$ 300
Subsequent Event [Member] | Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Repayments of Debt		$ 300

[1] In January 2019, $300 million of ComEd long-term debt due within one year was paid in full.

[2] Substantially all of ComEd’s assets other than expressly excepted property and substantially all of PECO’s, Pepco's, DPL's and ACE's assets are subject to the liens of their respective mortgage indentures.

[3] Includes capital lease obligations of $36 million and $53 million at December 31, 2018 and 2017, respectively. Lease payments of $21 million, $5 million, $1 million, $1 million, less than $1 million, and $8 million will be made in 2019, 2020, 2021, 2022, 2023, and thereafter, respectively.

[4] Includes financing related to Albany Green Energy, LLC (AGE). During the third quarter of 2017, Generation retired $228 million of its outstanding debt balance.

[5] Excludes interest on CEU Upstream nonrecourse debt, see discussion below.

[6] Amounts owed to these financing trusts are recorded as Long-term debt to financing trusts within Exelon’s Consolidated Balance Sheets.

[7] Includes Generation’s capital lease obligations of $14 million and $18 million at December 31, 2018 and 2017, respectively. Generation will make lease payments of $7 million, $5 million, $1 million, and $1 million in 2019, 2020, 2021, and 2022, respectively. Lease payments of less than $1 million annually will be made from 2023 through expiration of the final capital lease in 2024.

[8] Includes financing related to Albany Green Energy, LLC (AGE). During the third quarter of 2017, Generation retired $228 million of its outstanding debt balance.

[9] Excludes interest on CEU Upstream nonrecourse debt, see discussion below.

[10] In January 2019, the $300 million balance was paid in full.

[11] Substantially all of ComEd’s assets, other than expressly excepted property, are subject to the lien of its mortgage indenture.

[12] Includes ComEd’s capital lease obligations of $8 million at both December 31, 2018 and 2017, respectively. Lease payments of less than $1 million annually will be made from 2019 through expiration at 2053.

[13] Amount owed to this financing trust is recorded as Long-term debt to financing trust within ComEd’s Consolidated Balance Sheets.

[14] Amounts owed to this financing trust are recorded as Long-term debt to financing trusts within PECO’s Consolidated Balance Sheets.

[15] Substantially all of PECO’s assets are subject to the lien of its mortgage indenture.

[16] Substantially all of Pepco's, DPL's, and ACE's assets are subject to the lien of its respective mortgage indenture.

[17] Includes Pepco's capital lease obligations of $14 million and $27 million at December 31, 2018 and 2017, respectively.

[18] Transition bonds are recorded as part of Long-term debt within ACE's Consolidated Balance Sheets.

[19] Substantially all of Pepco's assets are subject to the lien of its respective mortgage indenture.

[20] Includes capital lease obligations of $14 million and $27 million at December 31, 2018 and 2017, respectively. Lease payments of $14 million will be made in 2019.

[21] Substantially all of DPL's assets are subject to the lien of its respective mortgage indenture.

[22] Substantially all of ACE's assets are subject to the lien of its respective mortgage indenture.

[23] Maturities of ACE's Transition Bonds outstanding at December 31, 2018 are $18 million in 2019, $20 million in 2020 and $21 million in 2021.