Debt and Credit Agreements - Retirement and Redemptions of Current and Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Exelon Generation Co L L C [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member]	Sep. 30, 2014 Baltimore Gas and Electric Company [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member]	Sep. 30, 2014 Commonwealth Edison Co [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member]	Sep. 30, 2013 Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] Junior Subordinated Debt [Member]	Sep. 30, 2013 Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] Armstrong Co Tax Exempt, 5% December 1,2042 [Member]	Sep. 30, 2013 Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] MEDCO Tax-Exempt Bonds [Member]	Sep. 30, 2014 Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] Senior Notes [Member] SeniorSecuredNotes525January152014Member [Member]	Sep. 30, 2014 Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] Capital Lease Obligations [Member] Kennett Square Capital Lease, 7.83%, September 20, 2020 [Member]	Sep. 30, 2013 Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] Capital Lease Obligations [Member] Kennett Square Capital Lease, 7.83%, September 20, 2020 [Member]	Sep. 30, 2014 Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] Capital Lease Obligations [Member] ExgenRenewables425February62021 [Member]	Sep. 30, 2014 Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] Capital Lease Obligations [Member] AVSR [Member]	Sep. 30, 2014 Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] Capital Lease Obligations [Member] Clear Horizon solar [Member]	Sep. 30, 2014 Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] Capital Lease Obligations [Member] Sacramento Solar [Member]	Sep. 30, 2013 Long Term Debt Retirements [Member] Baltimore Gas and Electric Company [Member]	Sep. 30, 2013 Long Term Debt Retirements [Member] Baltimore Gas and Electric Company [Member] Rate Stabilization Bonds, April 1, 2017 [Member]	Sep. 30, 2013 Long Term Debt Retirements [Member] Baltimore Gas and Electric Company [Member] Medium Term, Notes 6.73% 6.75% June 15, 2012 [Member]	Sep. 30, 2013 Long Term Debt Retirements [Member] Baltimore Gas and Electric Company [Member] Senior Notes [Member]	Sep. 30, 2014 Long Term Debt Retirements [Member] Baltimore Gas and Electric Company [Member] Rate Stabilization Bonds, April 1, 2017 [Member]	Sep. 30, 2014 Long Term Debt Retirements [Member] Commonwealth Edison Co [Member] First Mortgage Bonds [Member]	Sep. 30, 2014 Long Term Debt Retirements [Member] Commonwealth Edison Co [Member] First Mortgage Bonds [Member] FirstMortgageBond163January12014 [Member]	Sep. 30, 2014 Fixed Rate Debt [Member] Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] Pollution Control Notes [Member]	Sep. 30, 2014 Fixed Rate Debt [Member] Long Term Debt Retirements [Member] Baltimore Gas and Electric Company [Member] Rate Stabilization Bonds, April 1, 2017 [Member]	Sep. 30, 2014 Fixed Rate Debt [Member] Long Term Debt Retirements [Member] Commonwealth Edison Co [Member] Pollution Control Notes [Member]	Sep. 30, 2014 Continetal Wind [Member] Long Term Debt Retirements [Member] Exelon Generation Co L L C [Member] Continental Wind 6000 February 28, 2033 [Member]	Sep. 30, 2013 Minimum [Member] Long Term Debt Retirements [Member] Baltimore Gas and Electric Company [Member] Rate Stabilization Bonds, April 1, 2017 [Member]	Sep. 30, 2013 Maximum [Member] Long Term Debt Retirements [Member] Baltimore Gas and Electric Company [Member] Rate Stabilization Bonds, April 1, 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 131											$ 500	$ 2		$ 3	$ 4	$ 1	$ 1	$ 33			$ 400	$ 35	$ 9	$ 600	$ 20		$ 17	$ 20
Interest Rate									8.625%	7.625%	7.50%	5.35%	7.83%	7.83%			2.56%	2.56%	5720000.00%		2.563%	6125000.00%		4.40%	1.63%	4.10%	5.72%	5.85%	6.00%	1.93%	1.95%
Long-term Debt, Excluding Current Maturities	$ 19,200	$ 17,623	$ 6,741	$ 5,645	$ 1,904	$ 1,941	$ 5,448	$ 5,058	$ 450	$ 125	$ 127			$ 2						$ 18	$ 1