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Income Taxes - Summary of Interest Receivable (Payable) (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
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Income Taxes [Line Items] |  |
Net Interest Receivable Payable Related To Uncertain Tax Positions | $ 236 | $ 233
Unrecognized Tax Benefits, Income Tax Penalties Accrued | (17) | (17)
Exelon Generation Co L L C [Member] |  |
Income Taxes [Line Items] |  |
Net Interest Receivable Payable Related To Uncertain Tax Positions | (2) | (3)
Unrecognized Tax Benefits, Income Tax Penalties Accrued | 0 | 0
Commonwealth Edison Co [Member] |  |
Income Taxes [Line Items] |  |
Net Interest Receivable Payable Related To Uncertain Tax Positions | 4 | 4
Unrecognized Tax Benefits, Income Tax Penalties Accrued | 0 | 0
PECO Energy Co [Member] |  |
Income Taxes [Line Items] |  |
Net Interest Receivable Payable Related To Uncertain Tax Positions | 0 | 0
Unrecognized Tax Benefits, Income Tax Penalties Accrued | 0 | 0
Baltimore Gas and Electric Company [Member] |  |
Income Taxes [Line Items] |  |
Net Interest Receivable Payable Related To Uncertain Tax Positions | 0 | 0
Unrecognized Tax Benefits, Income Tax Penalties Accrued | 0 | 0
Pepco Holdings LLC [Member] |  |
Income Taxes [Line Items] |  |
Net Interest Receivable Payable Related To Uncertain Tax Positions | 1 | 2
Unrecognized Tax Benefits, Income Tax Penalties Accrued | 0 | 0
Potomac Electric Power Company [Member] |  |
Income Taxes [Line Items] |  |
Net Interest Receivable Payable Related To Uncertain Tax Positions | 0 | 0
Unrecognized Tax Benefits, Income Tax Penalties Accrued | 0 | 0
Delmarva Power & Light Company [Member] |  |
Income Taxes [Line Items] |  |
Net Interest Receivable Payable Related To Uncertain Tax Positions | 0 | 0
Unrecognized Tax Benefits, Income Tax Penalties Accrued | 0 | 0
Atlantic City Electric Company [Member] |  |
Income Taxes [Line Items] |  |
Net Interest Receivable Payable Related To Uncertain Tax Positions | 0 | 0
Unrecognized Tax Benefits, Income Tax Penalties Accrued | $ 0 | $ 0

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- Definition The amount of net interest receivable (payable) recognized for uncertain tax positions as of the balance sheet date. + References No definition available. + Details
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- Definition Amount of statutory penalties accrued for a tax position claimed or expected to be claimed by the entity, in its tax return. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
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