Debt and Credit Agreements - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Short-term Loan Agreements [Abstract]
Long-term Debt, Current Maturities	$ 2,153	$ 1,622
Nonrecourse Debt [Abstract]
Long-term Debt	32,655
Long-term debt, gross	$ 32,523	30,702
London Interbank Offered Rate (LIBOR) [Member] \| Minimum [Member]
Nonrecourse Debt [Abstract]
Debt Instrument, Basis Spread on Variable Rate	0.90%
London Interbank Offered Rate (LIBOR) [Member] \| Maximum [Member]
Nonrecourse Debt [Abstract]
Debt Instrument, Basis Spread on Variable Rate	1.275%
DOE Project Financing, 2.82% January 5, 2037 [Member] \| Non Recourse Debt [Member]
Nonrecourse Debt [Abstract]
Debt Instrument, Basis Spread on Variable Rate	0.375%
Corporate, Non-Segment [Member]
Short-term Loan Agreements [Abstract]
Long-term Debt, Current Maturities	$ 1,150	300
Notes Receivable, Related Parties	319	324
Nonrecourse Debt [Abstract]
Long-term Debt	7,289
Long-term debt, gross	7,289	7,589
Due from Affiliate, Noncurrent	$ 319	324
Corporate, Non-Segment [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Nonrecourse Debt [Abstract]
Debt Instrument, Basis Spread on Variable Rate	1.275%
Corporate, Non-Segment [Member] \| ShortTermDebt03232017 [Member]
Short-term Loan Agreements [Abstract]
Short-Term Loans	$ 500
Corporate, Non-Segment [Member] \| ShortTermDebt03232017 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Short-term Loan Agreements [Abstract]
Short-Term Loans, Interest rate terms	0.65
Corporate, Non-Segment [Member] \| ShortTermDebt03242021 [Member]
Short-term Loan Agreements [Abstract]
Short-Term Loans	$ 200
Corporate, Non-Segment [Member] \| ShortTermDebt03242021 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Short-term Loan Agreements [Abstract]
Short-Term Loans, Interest rate terms	0.65
Corporate, Non-Segment [Member] \| ShortTermDebt03312021.1 [Member]
Short-term Loan Agreements [Abstract]
Short-Term Loans	$ 150
Corporate, Non-Segment [Member] \| ShortTermDebt03312021.1 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Short-term Loan Agreements [Abstract]
Short-Term Loans, Interest rate terms	0.65
Corporate, Non-Segment [Member] \| ShortTermDebt03312021.2 [Member]
Short-term Loan Agreements [Abstract]
Short-Term Loans	$ 150
Corporate, Non-Segment [Member] \| ShortTermDebt03312021.2 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Short-term Loan Agreements [Abstract]
Short-Term Loans, Interest rate terms	0.65
Commonwealth Edison Co [Member]
Short-term Loan Agreements [Abstract]
Long-term Debt, Current Maturities	$ 0	350
Nonrecourse Debt [Abstract]
Long-term Debt	10,092
Long-term debt, gross	$ 9,887	9,087
Commonwealth Edison Co [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Nonrecourse Debt [Abstract]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Commonwealth Edison Co [Member] \| ShortTermDebt01252021.1
Short-term Loan Agreements [Abstract]
Short-Term Loans	$ 125
Commonwealth Edison Co [Member] \| ShortTermDebt01252021.1 \| London Interbank Offered Rate (LIBOR) [Member]
Short-term Loan Agreements [Abstract]
Short-Term Loans, Interest rate terms	0.50
Commonwealth Edison Co [Member] \| ShortTermDebt01252021.2
Short-term Loan Agreements [Abstract]
Short-Term Loans	$ 125
Commonwealth Edison Co [Member] \| ShortTermDebt01252021.2 \| London Interbank Offered Rate (LIBOR) [Member]
Short-term Loan Agreements [Abstract]
Short-Term Loans, Interest rate terms	0.75
Delmarva Power & Light Company [Member]
Short-term Loan Agreements [Abstract]
Long-term Debt, Current Maturities	$ 79	79
Nonrecourse Debt [Abstract]
Long-term Debt	1,821
Long-term debt, gross	$ 1,821	$ 1,687
Delmarva Power & Light Company [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Nonrecourse Debt [Abstract]
Debt Instrument, Basis Spread on Variable Rate	1.00%

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

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Amount of receivables due from an entity that is affiliated with the reporting entity by means of direct or indirect ownership, due after 1 year (or 1 business cycle).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount of borrowings from a bank classified as other, maturing within one year or operating cycle, if longer.

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