Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net cash flows provided by operating activities	$ 6,659	$ 8,644	$ 7,480
Cash flows from investing activities
Other investing activities	12	58	(43)
Net cash flows used in investing activities	(7,260)	(7,834)	(7,971)
Cash flows from financing activities
Changes in short-term borrowings	781	(338)	(261)
Proceeds from short-term borrowings with maturities greater than 90 days	0	126	621
Issuance of long-term debt	1,951	3,115	3,470
Retirement of long-term debt	(1,287)	(1,786)	(2,490)
Common stock issued from treasury stock	0	0	1,150
Dividends paid on common stock	(1,408)	(1,332)	(1,236)
Proceeds from employee stock plans	112	105	150
Other financing activities	(82)	(108)	(83)
Net cash flows provided by (used in) financing activities	(58)	(219)	767
(Decrease) Increase in cash, cash equivalents and restricted cash	(659)	591	276
Cash, cash equivalents and restricted cash at beginning of period	1,349	898	635
Cash, cash equivalents and restricted cash at end of period	587	1,349	898
Exelon Corporate [Member]
Net cash flows provided by operating activities	1,948	2,576	1,914
Cash flows from investing activities
Changes in Exelon intercompany money pool	95	1	(129)
Investment in affiliates	(1,071)	(1,231)	(1,710)
Other investing activities	0	0	(5)
Net cash flows used in investing activities	(976)	(1,230)	(1,844)
Cash flows from financing activities
Changes in short-term borrowings	136	0	0
Proceeds from short-term borrowings with maturities greater than 90 days	0	0	500
Retirement of long-term debt	0	0	(569)
Common stock issued from treasury stock	0	0	1,150
Dividends paid on common stock	(1,408)	(1,332)	(1,236)
Proceeds from employee stock plans	112	105	150
Other financing activities	0	(4)	(9)
Net cash flows provided by (used in) financing activities	(1,160)	(1,231)	(14)
(Decrease) Increase in cash, cash equivalents and restricted cash	(188)	115	56
Cash, cash equivalents and restricted cash at beginning of period	189	74	18
Cash, cash equivalents and restricted cash at end of period	$ 1	$ 189	$ 74