Decommission fund to pay for the costs of decontaminating and decommissioning of facilities through collection of revenues derived from utility assessments and government appropriations. Decommission fund investment for the process whereby a power station, at the end of its economic life, is taken permanently out of service and its site made available for other purposes. In the case of a nuclear station this comprises three different states of clearance. Immediately after the final closure, radioactive material such as nuclear fuel and operational waste is removed and the buildings surrounding the reactor shield are dismantled and finally the reactor itself is dismantled.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_DecommissioningFundInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Asset Retirement Obligations - Unrealized Gain on NDT Funds (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Asset Retirement Obligations [Line Items]
Decommissioning Fund Investments	$ 11,661	$ 13,272
Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Decommissioning Fund Investments	11,661	13,272
Collateral Pledged [Member] \| Unregulated Operation [Member] \| Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Unrealized Gain (Loss) on Investments	(483)	521	$ 194
Collateral Pledged [Member] \| Regulated Operation [Member] \| Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Unrealized Gain (Loss) on Investments	(715)	455	$ 216
Assets, Total [Member]
Asset Retirement Obligations [Line Items]
Decommissioning Fund Investments	$ 12,695	$ 13,349