Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net cash flows provided by (used in) operating activities	$ 8,644	$ 7,480	$ 8,461
Cash flows from investing activities
Other investing activities	58	(43)	(153)
Net cash flows provided by (used in) investing activities	(7,834)	(7,971)	(15,450)
Cash flows from financing activities
Issuance of long-term debt	3,115	3,470	4,716
Proceeds from short-term borrowings with maturities greater than 90 days	126	621	240
Retirement of long-term debt	(1,786)	(2,490)	(1,936)
Common stock issued from treasury stock	0	1,150	0
Dividends paid on common stock	(1,332)	(1,236)	(1,166)
Proceeds from employee stock plans	105	150	55
Other financing activities	(108)	(83)	(85)
Net cash flows provided by (used in) financing activities	(219)	767	1,191
Increase (Decrease) in cash, cash equivalents and restricted cash	591	276	(5,798)
Cash, cash equivalents and restricted cash at beginning of period	898	635	6,502
Cash, cash equivalents and restricted cash at end of period	1,349	898	635
Exelon Corporate [Member]
Net cash flows provided by (used in) operating activities	2,581	1,921	1,029
Cash flows from investing activities
Changes in Exelon intercompany money pool	1	(129)	1,390
Investment in affiliates	(1,236)	(1,717)	(1,757)
Acquisition of business	0	0	6,962
Other investing activities	0	(5)	5
Net cash flows provided by (used in) investing activities	(1,235)	(1,851)	(7,324)
Cash flows from financing activities
Issuance of long-term debt	0	0	1,800
Proceeds from short-term borrowings with maturities greater than 90 days	0	500	0
Retirement of long-term debt	0	(569)	(46)
Common stock issued from treasury stock	0	1,150	0
Dividends paid on common stock	(1,332)	(1,236)	(1,166)
Proceeds from employee stock plans	105	150	55
Other financing activities	(4)	(9)	(20)
Net cash flows provided by (used in) financing activities	(1,231)	(14)	623
Increase (Decrease) in cash, cash equivalents and restricted cash	115	56	(5,672)
Cash, cash equivalents and restricted cash at beginning of period	74	18	5,690
Cash, cash equivalents and restricted cash at end of period	$ 189	$ 74	$ 18