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Derivative Financial Instruments - Schedule of Notional Amounts Outstanding (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
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Derivative [Line Items] |  |  |
Derivative, Notional Amount | $ 5,991 | $ 3,606 |
Not Designated as Hedging Instrument, Economic Hedge [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Notional Amount | 1,688 | 95 |
Not Designated as Hedging Instrument, Economic Hedge [Member] | Foreign Exchange Contract [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Notional Amount | 268 | 94 |
Not Designated as Hedging Instrument, Economic Hedge [Member] | Interest Rate Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Notional Amount | 1,420 | 1 | [1]
Exelon Generation Co L L C [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Notional Amount | 888 | 95 |
Exelon Generation Co L L C [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member] | Foreign Exchange Contract [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Notional Amount | 268 | 94 |
Exelon Generation Co L L C [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member] | Interest Rate Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Notional Amount | 620 | 1 |
Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Notional Amount | 0 | 636 |
Corporate, Non-Segment [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Notional Amount | 800 | 0 |
Corporate, Non-Segment [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member] | Foreign Exchange Contract [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Notional Amount | 0 | 0 |
Corporate, Non-Segment [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member] | Interest Rate Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Notional Amount | 800 | 0 |
Corporate, Non-Segment [Member] | Fair Value Hedging [Member] | Interest Rate Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Notional Amount | $ 0 | $ 800 |
[1] | On July 1, 2018, Exelon and Generation de-designated its fair value and cash flow hedges. The table excludes amounts of $800 million of fixed-to-floating hedges that were previously designated as fair value hedges by Exelon and $636 million of floating-to-fixed hedges that were previously designated as cash flow hedges by Exelon and Generation as of December 31, 2017.

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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