Debt and Credit Agreements - Retirement and Redemptions of Current and Long-Term Debt (Details) - USD ($)			3 Months Ended
	Apr. 20, 2016	Apr. 01, 2016	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities			$ 29,314,000,000		$ 23,645,000,000
Repayments of Long-term Debt			116,000,000	$ 580,000,000
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Interest Rate					2.74%
Long-term Debt, Excluding Current Maturities			7,945,000,000		$ 7,936,000,000
Repayments of Long-term Debt			$ 94,000,000	18,000,000
Exelon Generation Co L L C [Member] | CEU Credit Agreement [Member]
Debt Instrument [Line Items]
Interest Rate			3.19%
Exelon Generation Co L L C [Member] | ExGen Texas Power [Member]
Debt Instrument [Line Items]
Interest Rate			5.00%
Repayments of Long-term Debt			$ 2,000,000
Exelon Generation Co L L C [Member] | Continental Wind 6000 February 28, 2033 [Member]
Debt Instrument [Line Items]
Interest Rate			6.00%
Repayments of Long-term Debt			$ 15,000,000
Exelon Generation Co L L C [Member] | AVSR [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt			$ 5,000,000
Exelon Generation Co L L C [Member] | AVSR [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate			2.29%
Exelon Generation Co L L C [Member] | AVSR [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest Rate			3.056%
Exelon Generation Co L L C [Member] | Clear Horizon solar [Member]
Debt Instrument [Line Items]
Interest Rate			2.56%
Repayments of Long-term Debt			$ 32,000,000
Exelon Generation Co L L C [Member] | Sacramento Solar [Member]
Debt Instrument [Line Items]
Interest Rate			2.58%
Repayments of Long-term Debt			$ 33,000,000
Exelon Generation Co L L C [Member] | Capital Lease Obligations [Member] | Kennett Square Capital Lease, 7.83%, September 20, 2020 [Member]
Debt Instrument [Line Items]
Interest Rate			7.83%
Repayments of Long-term Debt			$ 1,000,000
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Repayments of Bank Debt		$ 1,000,000
Interest Rate		5.72%
Long-term Debt, Excluding Current Maturities			1,481,000,000		1,480,000,000
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities			5,845,000,000		5,844,000,000
Potomac Electric Power Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities			2,341,000,000		2,340,000,000
Repayments of Long-term Debt			0	12,000,000
Atlantic City Electric Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities			1,144,000,000		1,153,000,000
Repayments of Long-term Debt	$ 3,000,000.0000		$ 11,000,000	$ 10,000,000
Atlantic City Electric Company [Member] | Transition Bonds555October2023 [Member]
Debt Instrument [Line Items]
Interest Rate			5.55%
Repayments of Secured Debt			$ 8,000,000.0000
Repayments of Long-term Debt	$ 8,000,000.0000
Atlantic City Electric Company [Member] | Transition Bonds505October2020 [Member]
Debt Instrument [Line Items]
Interest Rate			5.05%
Repayments of Secured Debt			$ 3,000,000.0000
CEU Holdings, LLC [Member]
Debt Instrument [Line Items]
Long-term Debt			61,000,000		$ 68,000,000
CEU Holdings, LLC [Member] | CEU Credit Agreement [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt			$ 7,000,000