Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			$ 490	$ 194
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			490	193
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 312	$ 87	494	214
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	312	87	494	214
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Operating revenues [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(240)	24	(323)	199
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Operating revenues [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(240)	24	(323)	199
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Purchased power and fuel [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	552	63	817	15
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Purchased power and fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 552	$ 63	$ 817	$ 15