XML 18 R28.htm IDEA: XBRL DOCUMENT v3.20.1
Components of Accrued Revenue (Detail) - USD ($)
$ in Millions
Mar. 31, 2020
Dec. 31, 2019
Mar. 31, 2019
Deferred Revenue Arrangement [Line Items]      
Regulatory Assets – Current $ 28.4 $ 35.8 $ 29.4
Total Accrued Revenue 38.6 50.0 40.2
Unbilled Revenues      
Deferred Revenue Arrangement [Line Items]      
Regulatory Assets – Current 10.2 14.2 10.8
Regulatory Assets      
Deferred Revenue Arrangement [Line Items]      
Regulatory Assets – Current $ 28.4 $ 35.8 $ 29.4