Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Balance Sheet (Details) - USD ($) shares in Millions, $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents		$ 663	$ 587	$ 1,349	$ 898
Accounts receivable
Mark-to-market derivative assets, current		644	679
Regulatory assets, current		1,228	1,170
Other		1,609	905
Total current assets		12,562	12,037
Property, plant and equipment, net		82,584	80,233
Deferred debits and other assets
Regulatory assets, noncurrent		8,759	8,335
Other		2,982	3,197
Total assets	[1]	129,317	124,977
Current liabilities
Short-term borrowings		2,031	1,370
Long-term debt due within one year		1,819	4,710
Accounts payable		3,562	3,560
Accrued expenses		2,078	1,981
Payables to affiliates, current		5	5
Regulatory liabilities, current		581	406
Other		1,264	1,331
Total current liabilities		12,771	14,185
Long-term debt		35,093	31,329
Deferred credits and other liabilities
Regulatory liabilities, noncurrent		9,485	9,986
Pension obligations		4,503	4,247
Non-pension postretirement benefits obligations		2,011	2,076
Other		2,942	3,064
Total deferred credits and other liabilities		46,195	44,500
Total liabilities	[1]	94,449	90,404
Commitments and contingencies
Shareholders’ equity
Common stock		19,373	19,274
Treasury stock, at cost		(123)	(123)
Retained earnings		16,735	16,267
Accumulated other comprehensive loss, net		(3,400)	(3,194)
Total shareholders’ equity		32,585	32,224
Total liabilities and equity		$ 129,317	$ 124,977
Common Stock, Shares Authorized		2,000	2,000
Common Stock, Shares, Outstanding		976	973
Treasury Stock, Shares		2	2
Exelon Corporate [Member]
Current assets
Cash and cash equivalents		$ 63	$ 1	$ 189	$ 74
Accounts receivable
Other accounts receivable		354	168
Accounts receivable from affiliates, current		11	41
Mark-to-market derivative assets, current		0	3
Note receivable from affiliates, current		598	679
Regulatory assets, current		315	253
Other		4	4
Total current assets		1,345	1,149
Property, plant and equipment, net		46	47
Deferred debits and other assets
Regulatory assets, noncurrent		3,816	3,772
Investments in affiliates		43,149	42,245
Deferred income taxes		1,625	1,524
Notes receivable from affiliates, noncurrent		324	329
Other		312	308
Total deferred debits and other assets		49,226	48,178
Total assets		50,617	49,374
Current liabilities
Short-term borrowings		500	636
Long-term debt due within one year		300	1,458
Accounts payable		1	1
Accrued expenses		76	131
Payables to affiliates, current		457	363
Regulatory liabilities, current		4	13
Pension obligations		92	77
Other		4	10
Total current liabilities		1,434	2,689
Long-term debt		7,418	5,717
Deferred credits and other liabilities
Regulatory liabilities, noncurrent		32	31
Pension obligations		8,351	7,960
Non-pension postretirement benefits obligations		387	403
Deferred income taxes		348	263
Other		62	87
Total deferred credits and other liabilities		9,180	8,744
Total liabilities		18,032	17,150
Commitments and contingencies
Shareholders’ equity
Common stock		19,373	19,274
Treasury stock, at cost		(123)	(123)
Retained earnings		16,735	16,267
Accumulated other comprehensive loss, net		(3,400)	(3,194)
Total shareholders’ equity		32,585	32,224
Total liabilities and equity		$ 50,617	$ 49,374
Common Stock, Shares Authorized		2,000	2,000
Common Stock, Shares, Outstanding		976	973
Treasury Stock, Shares		2	2

[1] Exelon’s consolidated assets include $10,200 million and $9,532 million at December 31, 2020 and 2019, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,598 million and $3,473 million at December 31, 2020 and 2019, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 23–Variable Interest Entities for additional information.