XML 40 R26.htm IDEA: XBRL DOCUMENT v3.20.2
Components of Gas and Electric Operating Revenue (Detail) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues $ 87.4 $ 85.3 $ 301.7 $ 320.9
Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 80.8 77.8 304.4 332.8
Rate Adjustment Mechanism Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 6.6 7.5 (2.7) (11.9)
Gas Segment        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 27.5 24.9 131.4 143.9
Gas Segment | Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 20.0 20.5 130.9 160.0
Gas Segment | Rate Adjustment Mechanism Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 7.5 4.4 0.5 (16.1)
Electric        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 59.9 60.4 170.3 177.0
Electric | Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 60.8 57.3 173.5 172.8
Electric | Rate Adjustment Mechanism Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues (0.9) 3.1 (3.2) 4.2
Residential | Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 42.3 38.2 152.3 156.2
Residential | Gas Segment | Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 7.0 6.9 52.4 61.4
Residential | Electric | Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 35.3 31.3 99.9 94.8
C&I | Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 35.7 37.0 141.6 161.7
C&I | Gas Segment | Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 11.6 12.5 72.9 89.5
C&I | Electric | Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 24.1 24.5 68.7 72.2
Other | Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 2.8 2.6 10.5 14.9
Other | Gas Segment | Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues 1.4 1.1 5.6 9.1
Other | Electric | Billed and Unbilled Revenue        
Operating Revenues [Line Items]        
Total Gas and Electric Operating Revenues $ 1.4 $ 1.5 $ 4.9 $ 5.8