Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Related Party Transactions - Summary of Related Party Transactions (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments		$ (32)	$ (24)	$ (7)
Due to Affiliate, Current		360	706
Exelon Corporate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	[1]	25	51	43
Interest income from affiliates, net		40	39	43
Income (Loss) from Equity Method Investments		4,398	1,521	2,461
Cash contributions received from affiliates		1,879	1,912	3,209
Accounts receivable from affiliates		33	48
Receivables from affiliates		217	88
Investments in affiliates		39,272	34,869
Total receivable from affiliates (noncurrent)		910	922
Due to Affiliate, Current		360	706
Exelon Corporate [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	[1]	23	51	43
Interest income from affiliates, net		3	0	0
Income (Loss) from Equity Method Investments		1	1	0
Accounts receivable from affiliates	[1]	1	15
Receivables from affiliates	[1]	217	88
Investments in affiliates	[1]	196	194
Exelon Corporate [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates		2	0	0
Investments in affiliates		(6)	(6)
Exelon Corporate [Member] | Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Interest income from affiliates, net		37	39	43
Income (Loss) from Equity Method Investments		2,694	496	1,371
Accounts receivable from affiliates		21	22
Investments in affiliates		13,635	11,488
Total receivable from affiliates (noncurrent)	[2]	910	922
Exelon Corporate [Member] | Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates		3	3
Due to Affiliate, Current		0	345
Exelon Corporate [Member] | PECO Energy Co [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates		1	1
Exelon Corporate [Member] | Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates		1	1
Exelon Corporate [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates		6	6
Exelon Corporate [Member] | Exelon Energy Delivery Company LLC [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments	[3]	1,670	1,041	1,079
Investments in affiliates	[3]	25,082	23,003
Exelon Corporate [Member] | Potomac Capital Investment Affiliate [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments		1	6	0
Investments in affiliates		78	77
Exelon Corporate [Member] | UII LLC [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments		41	(9)	20
Investments in affiliates		268	92
Due to Affiliate, Current		360	361
Exelon Corporate [Member] | Exelon Transmission Company LLC [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments		(10)	(13)	(8)
Investments in affiliates		1	5
Exelon Corporate [Member] | VEBA [Member]
Related Party Transaction [Line Items]
Investments in affiliates		(4)	(5)
Exelon Corporate [Member] | Exelon Enterprise [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments		1	(1)	$ (1)
Investments in affiliates		$ 22	$ 21

[1] Exelon Corporate receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead.

[2] In connection with the debt obligations assumed by Exelon as part of the Constellation merger, Exelon and subsidiaries of Generation (former Constellation subsidiaries) assumed intercompany loan agreements that mirror the terms and amounts of the third-party debt obligations of Exelon, resulting in intercompany notes payable included in Long-Term Debt to affiliate on Generation’s Consolidated Balance Sheets and intercompany notes receivable at Exelon Corporate, which are eliminated in consolidation on Exelon’s Consolidated Balance Sheets.

[3] Exelon Energy Delivery Company, LLC consists of ComEd, PECO, BGE, PHI, Pepco, DPL and ACE.