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v3.19.1

Components of Gas and Electric Operating Revenue (Detail) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2019 | Mar. 31, 2018
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | $ 151.2 | $ 144.5
Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 161.9 | 153.0
Rate Adjustment Mechanism Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | (10.7) | (8.5)
Gas Segment |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 86.4 | 87.0
Gas Segment | Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 99.2 | 91.4
Gas Segment | Rate Adjustment Mechanism Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | (12.8) | (4.4)
Electric |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 64.8 | 57.5
Electric | Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 62.7 | 61.6
Electric | Rate Adjustment Mechanism Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 2.1 | (4.1)
Residential | Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 74.4 | 70.2
Residential | Gas Segment | Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 38.7 | 35.8
Residential | Electric | Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 35.7 | 34.4
C&I | Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 78.7 | 74.7
C&I | Gas Segment | Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 54.0 | 50.6
C&I | Electric | Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 24.7 | 24.1
Other | Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 8.8 | 8.1
Other | Gas Segment | Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | 6.5 | 5.0
Other | Electric | Billed and Unbilled Revenue |  |
Operating Revenues [Line Items] |  |
Total Gas and Electric Operating Revenues | $ 2.3 | $ 3.1

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- Definition Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045 + Details
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