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OPERATING REVENUES - DISAGGREGATION OF NATURAL GAS UTILITY OPERATING REVENUES BY CUSTOMER CLASS (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2018
Natural gas |  |
Disaggregation of Operating Revenues |  |
Number of days payment is due |  | 30 days
Revenues from contracts with customers |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | $ 1,635.7 | $ 5,599.3
Revenues from contracts with customers | Natural gas |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 403.8 | 2,190.9
Revenues from contracts with customers | Natural gas | Transferred over time |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 406.5 | 2,183.9
Revenues from contracts with customers | Natural gas | Transferred over time | Residential |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 204.7 | 1,346.9
Revenues from contracts with customers | Natural gas | Transferred over time | Commercial and industrial |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 77.0 | 568.5
Revenues from contracts with customers | Natural gas | Transferred over time | Total retail revenues |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 281.7 | 1,915.4
Revenues from contracts with customers | Natural gas | Transferred over time | Transport |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 62.1 | 248.5
Revenues from contracts with customers | Natural gas | Transferred over time | Other utility revenues |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 62.7 | 20.0
Wisconsin | Revenues from contracts with customers | Transferred over time |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 1,385.7 | 4,292.0
Wisconsin | Revenues from contracts with customers | Natural gas | Transferred over time |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 167.4 | 921.8
Wisconsin | Revenues from contracts with customers | Natural gas | Transferred over time | Residential |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 71.9 | 556.7
Wisconsin | Revenues from contracts with customers | Natural gas | Transferred over time | Commercial and industrial |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 35.0 | 286.4
Wisconsin | Revenues from contracts with customers | Natural gas | Transferred over time | Total retail revenues |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 106.9 | 843.1
Wisconsin | Revenues from contracts with customers | Natural gas | Transferred over time | Transport |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 13.9 | 51.3
Wisconsin | Revenues from contracts with customers | Natural gas | Transferred over time | Other utility revenues |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 46.6 | 27.4
Illinois | Revenues from contracts with customers | Transferred over time |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 193.3 | 974.8
Illinois | Revenues from contracts with customers | Natural gas | Transferred over time |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 193.2 | 974.6
Illinois | Revenues from contracts with customers | Natural gas | Transferred over time | Residential |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 112.7 | 609.0
Illinois | Revenues from contracts with customers | Natural gas | Transferred over time | Commercial and industrial |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 29.4 | 186.1
Illinois | Revenues from contracts with customers | Natural gas | Transferred over time | Total retail revenues |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 142.1 | 795.1
Illinois | Revenues from contracts with customers | Natural gas | Transferred over time | Transport |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 43.3 | 175.6
Illinois | Revenues from contracts with customers | Natural gas | Transferred over time | Other utility revenues |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 7.8 | 3.9
Other States | Revenues from contracts with customers | Transferred over time |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 49.9 | 299.3
Other States | Revenues from contracts with customers | Natural gas | Transferred over time |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 45.9 | 287.5
Other States | Revenues from contracts with customers | Natural gas | Transferred over time | Residential |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 20.1 | 181.2
Other States | Revenues from contracts with customers | Natural gas | Transferred over time | Commercial and industrial |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 12.6 | 96.0
Other States | Revenues from contracts with customers | Natural gas | Transferred over time | Total retail revenues |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 32.7 | 277.2
Other States | Revenues from contracts with customers | Natural gas | Transferred over time | Transport |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | 4.9 | 21.6
Other States | Revenues from contracts with customers | Natural gas | Transferred over time | Other utility revenues |  |
Disaggregation of Operating Revenues |  |
Revenues from contracts with customers | $ 8.3 | $ (11.3)

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