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Revenue Recognition Revenue Recognition (Allowance for Credit Losses) (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2021 | Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Allowance for Credit Loss | $ 53.9 | $ 52.3
Current period provisions | 8.8 |
Write-offs charged against allowance | (11.4) |
Recoveries of amounts previously written off | 4.2 |
Gas Distribution Operations |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Allowance for Credit Loss | 42.8 | 41.8
Current period provisions | 5.9 |
Write-offs charged against allowance | (9.0) |
Recoveries of amounts previously written off | 4.1 |
Electric Operations |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Allowance for Credit Loss | 10.3 | 9.7
Current period provisions | 2.9 |
Write-offs charged against allowance | (2.4) |
Recoveries of amounts previously written off | 0.1 |
Corporate and Other |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Allowance for Credit Loss | 0.8 | $ 0.8
Current period provisions | 0.0 |
Write-offs charged against allowance | 0.0 |
Recoveries of amounts previously written off | $ 0.0 |

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- Definition Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(7)(2)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121599878&loc=SL82895884-210446 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447 + Details
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