XML 40 R26.htm IDEA: XBRL DOCUMENT 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