Derivative Financial Instruments (Collateral and Contingent-Related Features) (Details) (USD $)
In Millions, unless otherwise specified |
Jun. 30, 2014
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Dec. 31, 2013
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Exelon Generation Co L L C [Member]
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Collateral And Contingent Related Features [Abstract] | ||||||||||
Aggregate fair value of derivatives with credit-risk-related contingent features | $ (1,102) | [1] | $ (1,056) | [1] | ||||||
Contractual right of offset related to derivative assets | 825 | [2] | 846 | [2] | ||||||
Net liability position after contractual right of offset | (277) | [3] | (210) | [3] | ||||||
Incremental collateral for loss of investment grade credit rating | 2,000 | 2,000 | ||||||||
Cash collateral held | 206 | |||||||||
Cash collateral posted | 623 | 72 | ||||||||
Letters of credit held | 34 | |||||||||
Letters of credit posted | 466 | 364 | ||||||||
Master Netting Arrangements [Abstract] | ||||||||||
Cash collateral received not offset against net derivative positions | 7 | 10 | ||||||||
Commonwealth Edison Co [Member]
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Collateral And Contingent Related Features [Abstract] | ||||||||||
Cash collateral held | 19 | |||||||||
Swap Contract Collateral Posting Limit [Abstract] | ||||||||||
Credit Derivative, Collateral Held Directly or by Third Parties Monetary Amount | 2 | |||||||||
PECO Energy Co [Member]
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Collateral And Contingent Related Features [Abstract] | ||||||||||
Incremental collateral for loss of investment grade credit rating | 26 | |||||||||
Baltimore Gas and Electric Company [Member]
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Collateral And Contingent Related Features [Abstract] | ||||||||||
Incremental collateral for loss of investment grade credit rating | $ 73 | |||||||||
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