Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			$ 1,244	$ 448
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			1,244	448
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 755	$ 248	1,248	462
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	755	248	1,248	462
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Operating revenues [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(637)	39	(961)	238
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	(637)	39	(961)	238
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Purchased power and fuel [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	1,392	209	2,209	224
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	$ 1,392	$ 209	$ 2,209	$ 224