Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net cash flows provided by operating activities	$ 7,480	$ 8,445	$ 7,616
Cash flows from investing activities
Payments to Acquire Businesses, Net of Cash Acquired		6,962	0
Proceeds from Sale and Collection of Lease Receivables	0	360	0
Capital expenditures	(7,584)	(8,553)	(7,624)
Change in restricted cash	(50)	(42)	66
Other investing activities	(43)	(153)	(119)
Net cash flows used in investing activities	(7,934)	(15,503)	(7,822)
Cash flows from financing activities
Changes in short-term borrowings	621	240	0
Issuance of long-term debt	3,470	4,716	6,709
Retirement of long-term debt	(2,490)	(1,936)	(2,687)
Proceeds from Issuance of Common Stock	0	0	1,868
Dividends paid on common stock	(1,236)	(1,166)	(1,105)
Proceeds from employee stock plans	150	55	32
Other financing activities	(83)	(85)	(99)
Net cash flows provided by financing activities	717	1,191	4,830
Increase (Decrease) in cash and cash equivalents	263	(5,867)	4,624
Cash and cash equivalents at beginning of period	635	6,502	1,878
Cash and cash equivalents at end of period	898	635	6,502
Exelon Corporate [Member]
Net cash flows provided by operating activities	1,921	1,029	3,071
Cash flows from investing activities
Payments to Acquire Businesses, Net of Cash Acquired	0
Increase (Decrease) Due from Affiliates	(129)	1,390	(1,217)
Increase (Decrease) in Due from Affiliates, Current	0	0	550
Investment in affiliates	(1,717)	(1,757)	(212)
Other investing activities	(5)	5	(55)
Net cash flows used in investing activities	(1,851)	(7,324)	(934)
Cash flows from financing activities
Issuance of long-term debt	0	1,800	4,200
Retirement of long-term debt	(569)	(46)	(2,263)
Proceeds from Issuance of Common Stock	0	0	1,868
Dividends paid on common stock	(1,236)	(1,166)	(1,105)
Proceeds from employee stock plans	150	55	32
Other financing activities	(9)	(20)	(58)
Net cash flows provided by financing activities	(14)	623	2,674
Increase (Decrease) in cash and cash equivalents	56	(5,672)	4,811
Cash and cash equivalents at beginning of period	18	5,690	879
Cash and cash equivalents at end of period	$ 74	$ 18	$ 5,690