Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net cash flows provided by operating activities	$ 4,235	$ 6,659	$ 8,644
Cash flows from investing activities
Other investing activities	18	12	58
Net cash flows used in investing activities	(4,336)	(7,260)	(7,834)
Cash flows from financing activities
Changes in short-term borrowings	161	781	(338)
Proceeds from short-term borrowings with maturities greater than 90 days	500	0	126
Issuance of long-term debt	7,507	1,951	3,115
Retirement of long-term debt	(6,440)	(1,287)	(1,786)
Dividends paid on common stock	(1,492)	(1,408)	(1,332)
Proceeds from employee stock plans	45	112	105
Other financing activities	(136)	(82)	(108)
Net cash flows provided by (used in) financing activities	145	(58)	(219)
(Decrease) Increase in cash, cash equivalents and restricted cash	44	(659)	591
Cash, cash equivalents and restricted cash at beginning of period	587	1,349	898
Cash, cash equivalents and restricted cash at end of period	663	587	1,349
Exelon Corporate [Member]
Net cash flows provided by operating activities	3,018	1,948	2,576
Cash flows from investing activities
Changes in Exelon/PHI intercompany money pool	(477)	95	1
Notes receivable from affiliates	550	0	0
Investment in affiliates	(1,969)	(1,071)	(1,231)
Net cash flows used in investing activities	(1,896)	(976)	(1,230)
Cash flows from financing activities
Changes in short-term borrowings	(136)	136	0
Issuance of long-term debt	2,000	0	0
Retirement of long-term debt	(1,450)	0	0
Dividends paid on common stock	(1,492)	(1,408)	(1,332)
Proceeds from employee stock plans	45	112	105
Other financing activities	(27)	0	(4)
Net cash flows provided by (used in) financing activities	(1,060)	(1,160)	(1,231)
(Decrease) Increase in cash, cash equivalents and restricted cash	62	(188)	115
Cash, cash equivalents and restricted cash at beginning of period	1	189	74
Cash, cash equivalents and restricted cash at end of period	$ 63	$ 1	$ 189