Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Statements of Operations and Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended								9 Months Ended	12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Expenses [Abstract]
Total operating expenses											$ 29,720	$ 28,200	$ 25,056
Operating Income (Loss)		$ 1,258	$ 1,475	$ 232	$ 1,296	$ 714	$ 1,267	$ 647	$ 483		4,260	3,112	4,409
Other income and (deductions)
Interest expense, net											(1,524)	(1,495)	(992)
Equity in losses of unconsolidated affiliates											(32)	(24)	(7)
Other, net											1,056	413	(46)
Total other income and (deductions)											(504)	(1,123)	(1,079)
Income before income taxes											3,756	1,989	3,330
Income taxes											(125)	761	1,073
Net Income (Loss)											3,849	1,204	2,250
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost, net of tax											56	48	46
Actuarial loss reclassified to periodic cost, net of tax											197	184	220
Unrealized gain (loss) on cash flow hedges, net of taxes										$ 0	3	2	9
Unrealized gain (loss) on marketable securities, net of taxes											4	(4)	(3)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax											6	1	0
Unrealized gain (loss) on foreign currency translation, net of taxes											7	10	(21)
Other comprehensive income (loss)											171	(36)	60
Comprehensive income											3,943	1,098	2,329
Exelon Corporate [Member]
Operating Expenses [Abstract]
Operating and maintenance											10	221	0
Operating and maintenance from affiliates	[1]										25	51	43
Other											4	4	4
Total operating expenses											39	276	47
Operating Income (Loss)											(39)	(276)	(47)
Other income and (deductions)
Interest expense, net											(315)	(312)	(168)
Equity in losses of unconsolidated affiliates											4,398	1,521	2,461
Interest income from affiliates, net											40	39	43
Other, net											1	7	(43)
Total other income and (deductions)											4,124	1,255	2,293
Income before income taxes											4,085	979	2,246
Income taxes											315	(155)	(23)
Net Income (Loss)											3,770	1,134	2,269
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost, net of tax											56	48	46
Actuarial loss reclassified to periodic cost, net of tax											197	184	220
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax											(10)	181	99
Unrealized gain (loss) on cash flow hedges, net of taxes											3	2	9
Unrealized gain (loss) on marketable securities, net of taxes											6	(4)	(3)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax											6	1	0
Unrealized gain (loss) on foreign currency translation, net of taxes											7	10	(21)
Other comprehensive income (loss)											173	(36)	60
Comprehensive income											$ 3,943	$ 1,098	$ 2,329

[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.