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, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Equity in earnings (losses) of unconsolidated affiliates		$ (28)	$ (32)	$ (24)
Payables to affiliates, current		5	5
Exelon Corporate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	[1]	9	25	51
Interest income from affiliates, net		42	40	39
Equity in earnings (losses) of unconsolidated affiliates		2,188	4,414	1,508
Cash contributions received from affiliates		2,302	1,879	1,912
Accounts receivable from affiliates, current		44	33
Note receivable from affiliates, current		216	217
Investments in affiliates		40,448	39,311
Notes receivable from affiliates, noncurrent		898	910
Payables to affiliates, current		360	360
Exelon Corporate [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	[1]	11	23	51
Interest income from affiliates, net		4	3	0
Equity in earnings (losses) of unconsolidated affiliates		0	1	1
Accounts receivable from affiliates, current	[1]	13	1
Note receivable from affiliates, current	[1]	116	217
Investments in affiliates	[1]	197	196
Exelon Corporate [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates		(2)	2	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		36	37	39
Equity in earnings (losses) of unconsolidated affiliates		369	2,710	483
Accounts receivable from affiliates, current		17	21
Note receivable from affiliates, current	[2]	100	0
Investments in affiliates		13,204	13,674
Notes receivable from affiliates, noncurrent	[2]	898	910
Exelon Corporate [Member] | Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates, current		4	3
Exelon Corporate [Member] | PECO Energy Co [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates, current		2	1
Exelon Corporate [Member] | Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates, current		2	1
Exelon Corporate [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates, current		6	6
Exelon Corporate [Member] | Exelon Energy Delivery Company LLC [Member]
Related Party Transaction [Line Items]
Interest income from affiliates, net	[3]	2	0	0
Equity in earnings (losses) of unconsolidated affiliates	[3]	1,835	1,670	1,041
Investments in affiliates	[3]	26,702	25,082
Exelon Corporate [Member] | Potomac Capital Investment Affiliate [Member]
Related Party Transaction [Line Items]
Equity in earnings (losses) of unconsolidated affiliates		(17)	1	6
Investments in affiliates		61	78
Exelon Corporate [Member] | UII LLC [Member]
Related Party Transaction [Line Items]
Equity in earnings (losses) of unconsolidated affiliates		0	41	(9)
Investments in affiliates		268	268
Payables to affiliates, current		360	360
Exelon Corporate [Member] | Exelon Transmission Company LLC [Member]
Related Party Transaction [Line Items]
Equity in earnings (losses) of unconsolidated affiliates		1	(10)	(13)
Investments in affiliates		1	1
Exelon Corporate [Member] | VEBA [Member]
Related Party Transaction [Line Items]
Investments in affiliates		(1)	(4)
Exelon Corporate [Member] | Exelon Enterprise [Member]
Related Party Transaction [Line Items]
Equity in earnings (losses) of unconsolidated affiliates		0	1	$ (1)
Investments in affiliates		$ 22	$ 22

[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 affiliates in Generation’s Consolidated Balance Sheets and intercompany notes receivable at Exelon Corporate, which are eliminated in consolidation in Exelon’s Consolidated Balance Sheets.

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