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Revenue Recognition (Revenue Recognition Under Previous Guidance) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Revenue Recognition Under Previous Guidance [Line Items] |  |  |
Total Operating Revenues | $ 5,114.5 | $ 4,874.6 | $ 4,492.5
Previous Accounting Guidance | Gas Distribution [Member] |  |  |
Revenue Recognition Under Previous Guidance [Line Items] |  |  |
Total Operating Revenues | 2,348.4 | 2,063.2 | 1,850.9
Previous Accounting Guidance | Gas Transportation [Member] |  |  |
Revenue Recognition Under Previous Guidance [Line Items] |  |  |
Total Operating Revenues | 1,055.2 | 1,021.5 | 964.6
Previous Accounting Guidance | Electric [Member] |  |  |
Revenue Recognition Under Previous Guidance [Line Items] |  |  |
Total Operating Revenues | 1,707.4 | 1,785.5 | 1,660.8
Previous Accounting Guidance | Other [Member] |  |  |
Revenue Recognition Under Previous Guidance [Line Items] |  |  |
Total Operating Revenues | $ 3.5 | $ 4.4 | $ 16.2

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- Definition [Line Items] for Revenue Recognition Under Previous Guidance [Table] + References No definition available. + Details
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- Definition The total amount of regulated operating revenues recognized during the period. + References No definition available. + Details
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- Details
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- Details
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