Regulatory Matters Regulatory Matters - Schedule of Revenue Increases (Decreases) (Details) - Commonwealth Edison Co [Member] - USD ($) $ in Millions				12 Months Ended
		Dec. 04, 2018	Apr. 16, 2018	Dec. 31, 2018	Dec. 31, 2017
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[1]			$ (44)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1],[2]			(26)
Electric Distribution [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount				$ (58)
Public Utilities, Approved Rate Increase (Decrease), Amount					$ 34
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[3]	$ (24)	$ (23)
Public Utilities, Requested Equity Capital Structure, Percentage		8.69%

[1] The time period for any formal challenges to the annual transmission formula rate update filings expired with no formal challenges submitted.

[2] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmVlYzRiNDIxOTkxNDRkN2ViNWYzYTRhOTVmMjFkNDYzfFRleHRTZWxlY3Rpb246MzY0MUFFQzNGNTE3Mzk3OTI2RjIxNTRFRUQyNkYyMzMM}

[3] Includes the annual ongoing TCJA tax savings further discussed below.