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Significant Accounting Policies Balance Sheet Classification of Deferred Taxes (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Other noncurrent assets | $ 1,575 | $ 1,330
Other noncurrent liabilities | 2,130 | 2,097
Commonwealth Edison Co [Member] |  |
Other noncurrent assets | 395 | 238
Other noncurrent liabilities | 630 | 562
Exelon Generation Co L L C [Member] |  |
Other noncurrent assets | 755 | 670
Other noncurrent liabilities | 610 | 658
PECO Energy Co [Member] |  |
Other noncurrent assets | 27 | 12
Other noncurrent liabilities | 76 | 86
Baltimore Gas and Electric Company [Member] |  |
Other noncurrent assets | 5 | 4
Other noncurrent liabilities | $ 73 | $ 56

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