Debt and Credit Agreements - Summary of Outstanding Long-term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 35,560	$ 34,911
Unamortized debt discount and premium, net	(72)	(66)
Unamortized Debt Issuance Expense	(214)	(216)
Fair value adjustment	765	795
Long-term debt due within one year	(4,710)	(1,349)
Long-term debt to financing trusts	390	390
Long-term debt	31,329	34,075
ComEd Financing III Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	206	206
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	$ 17,486	16,496
Secured Debt [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.70%
Secured Debt [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.90%
Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 10,685	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	$ 3,300	2,900
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	$ 412	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	$ 3	39
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	$ 154	188
Unamortized Debt Issuance Expense	$ 0	0
Notes Payable, Other Payables [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.53%
Notes Payable, Other Payables [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.99%
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
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	$ 55	73
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	$ 222	112
Tax-exempt Money Market Funds [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.63%
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	$ 10	22
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	$ 40	59
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	50
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	$ 1,182	1,253
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	$ 811	849
Non Recourse Variable Rate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.18%
Non Recourse Variable Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.91%
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	$ 206	206
Long-term Debt [Member] \| ComEd Financing III Affiliate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.35%
Long-term Debt [Member] \| PECO Trust III Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	$ 81	81
Long-term Debt [Member] \| PECO Trust III Affiliate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.75%
Long-term Debt [Member] \| PECO Trust III Affiliate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.38%
Long-term Debt [Member] \| PECO Trust IV Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	$ 103	103
Long-term Debt [Member] \| PECO Trust IV Affiliate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 7,943	8,759
Unamortized debt discount and premium, net	(5)	(6)
Unamortized Debt Issuance Expense	(42)	(51)
Fair value adjustment	78	91
Long-term debt due within one year	(3,182)	(906)
Debt and Lease Obligation	4,792	7,887
Long-term debt	4,464	6,989
Exelon Generation Co L L C [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 5,420	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	$ 412	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	$ 3	39
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	$ 115	164
Exelon Generation Co L L C [Member] \| Notes Payable, Other Payables [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.53%
Exelon Generation Co L L C [Member] \| Notes Payable, Other Payables [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.26%
Exelon Generation Co L L C [Member] \| Non Recourse Fixed Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 1,182	1,253
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	$ 811	849
Exelon Generation Co L L C [Member] \| Non Recourse Variable Rate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.18%
Exelon Generation Co L L C [Member] \| Non Recourse Variable Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.91%
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 8,586	8,187
Unamortized debt discount and premium, net	(27)	(23)
Unamortized Debt Issuance Expense	(68)	(63)
Long-term debt due within one year	(500)	(300)
Long-term debt to financing trusts	205	205
Debt and Lease Obligation	7,991	7,801
Long-term debt	7,991	7,801
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] \| PECO Trust III Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	0	0
Commonwealth Edison Co [Member] \| PECO Trust IV Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	0	0
Commonwealth Edison Co [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 8,578	8,179
Commonwealth Edison Co [Member] \| Secured Debt [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.55%
Commonwealth Edison Co [Member] \| Secured Debt [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.45%
Commonwealth Edison Co [Member] \| Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 8	8
Commonwealth Edison Co [Member] \| Notes Payable, Other Payables [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage
Commonwealth Edison Co [Member] \| Notes Payable, Other Payables [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.49%
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	$ 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	6.35%
PECO Energy Co [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 3,450	3,125
Unamortized debt discount and premium, net	(21)	(18)
Unamortized Debt Issuance Expense	(24)	(23)
Long-term debt to financing trusts	184	184
Debt and Lease Obligation	3,405	3,084
Long-term debt	3,405	3,084
PECO Energy Co [Member] \| ComEd Financing III Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	0	0
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	$ 3,400	3,075
PECO Energy Co [Member] \| Secured Debt [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.70%
PECO Energy Co [Member] \| Secured Debt [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.95%
PECO Energy Co [Member] \| Loans Payable [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 50	50
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	$ 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	6.75%
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	7.38%
PECO Energy Co [Member] \| Long-term Debt [Member] \| PECO Trust IV Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	$ 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	5.75%
PECO Energy Co [Member] \| Long-term Debt [Member] \| PECO Financing Trusts [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts	$ 184
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	3,300	2,900
Unamortized debt discount and premium, net	(9)	(6)
Unamortized Debt Issuance Expense	(21)	(18)
Long-term debt	3,270	2,876
Long-term debt	3,270	2,876
Baltimore Gas and Electric Company [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 3,300	2,900
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, Gross	$ 5,995	5,636
Unamortized debt discount and premium, net	4	4
Unamortized Debt Issuance Expense	(19)	(14)
Fair value adjustment	583	633
Long-term debt due within one year	(103)	(125)
Long-term debt	6,460	6,134
Long-term debt	6,460	6,134
Pepco Holdings LLC [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 5,508	5,242
Pepco Holdings LLC [Member] \| Secured Debt [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.76%
Pepco Holdings LLC [Member] \| Secured Debt [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	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	$ 30	16
Pepco Holdings LLC [Member] \| Notes Payable, Other Payables [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.54%
Pepco Holdings LLC [Member] \| Notes Payable, Other Payables [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.99%
Pepco Holdings LLC [Member] \| Tax-exempt Money Market Funds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 222	112
Pepco Holdings LLC [Member] \| Tax-exempt Money Market Funds [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.63%
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	$ 10	22
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	$ 40	59
Pepco Holdings LLC [Member] \| Transition Bonds [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage
Pepco Holdings LLC [Member] \| Transition Bonds [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.55%
Potomac Electric Power Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 2,897	2,751
Unamortized debt discount and premium, net	2	2
Unamortized Debt Issuance Expense	(35)	(34)
Long-term debt due within one year	(2)	(15)
Long-term debt	2,862	2,704
Long-term debt	2,862	2,704
Potomac Electric Power Company [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 2,775	2,735
Potomac Electric Power Company [Member] \| Secured Debt [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.05%
Potomac Electric Power Company [Member] \| Secured Debt [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.90%
Potomac Electric Power Company [Member] \| Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 12	16
Potomac Electric Power Company [Member] \| Notes Payable, Other Payables [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.54%
Potomac Electric Power Company [Member] \| Notes Payable, Other Payables [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.99%
Potomac Electric Power Company [Member] \| Tax-exempt Money Market Funds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 110	0
Potomac Electric Power Company [Member] \| Tax-exempt Money Market Funds [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.70%
Delmarva Power & Light Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 1,578	1,504
Unamortized debt discount and premium, net	1	2
Unamortized Debt Issuance Expense	(12)	(12)
Long-term debt due within one year	(79)
Long-term debt due within one year	(80)	(91)
Long-term debt	1,487	1,403
Long-term debt	1,487	1,403
Delmarva Power & Light Company [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 1,446	1,370
Delmarva Power & Light Company [Member] \| Secured Debt [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.76%
Delmarva Power & Light Company [Member] \| Secured Debt [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.27%
Delmarva Power & Light Company [Member] \| Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Finance Lease, Liability	$ 10	0
Delmarva Power & Light Company [Member] \| Notes Payable, Other Payables [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Lessee, Finance Lease, Discount Rate	3.54%
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	1.63%
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	$ 10	22
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, Gross	$ 1,335	1,196
Unamortized debt discount and premium, net	(1)	(1)
Unamortized Debt Issuance Expense	(7)	(7)
Long-term debt due within one year	(20)	(18)
Long-term debt	1,307	1,170
Long-term debt	1,307	1,170
Atlantic City Electric Company [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 1,287	1,137
Atlantic City Electric Company [Member] \| Secured Debt [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.38%
Atlantic City Electric Company [Member] \| Secured Debt [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.80%
Atlantic City Electric Company [Member] \| Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Finance Lease, Liability	$ 8	0
Atlantic City Electric Company [Member] \| Notes Payable, Other Payables [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Lessee, Finance Lease, Discount Rate	3.54%
Atlantic City Electric Company [Member] \| Transition Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 40	59
Atlantic City Electric Company [Member] \| Transition Bonds [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.55%
Parent Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 7,039	7,039
Unamortized debt discount and premium, net	(7)	(7)
Unamortized Debt Issuance Expense	39	47
Long-term debt due within one year	(1,458)	0
Long-term debt	5,717	7,147
Parent Company [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 5,889	5,889
Parent Company [Member] \| Senior Notes [Member] \| Minimum [Member]
Debt Instrument [Line Items]

Debt and Credit Agreements - Summary of Outstanding Long-term Debt (Details) - USD ($)
$ in Millions

Dec. 31, 2019

Dec. 31, 2018

Debt Instrument [Line Items]

Long-term Debt, Gross

$ 35,560

$ 34,911

Unamortized debt discount and premium, net

(72)

(66)

Unamortized Debt Issuance Expense

(214)