XML 59 R36.htm IDEA: XBRL DOCUMENT v3.7.0.1
Regulatory Matters (Regulatory Liabilities) (Details) - USD ($)
$ in Millions
Jun. 30, 2017
Dec. 31, 2016
Regulatory Liabilities [Line Items]    
Regulatory liabilities $ 665.8 $ 681.0
Cost of removal obligations [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 415.3 411.6
Electric transmission cost recovery [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 118.5 72.0
IPL's tax benefit riders [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 47.2 83.5
Commodity cost recovery [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 27.5 30.8
Energy efficiency cost recovery [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 19.6 20.5
Derivatives [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 11.4 31.5
Other [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 26.3 31.1
IPL [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 415.7 430.8
IPL [Member] | Cost of removal obligations [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 273.0 269.4
IPL [Member] | Electric transmission cost recovery [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 61.7 35.7
IPL [Member] | IPL's tax benefit riders [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 47.2 83.5
IPL [Member] | Commodity cost recovery [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 15.9 17.8
IPL [Member] | Derivatives [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 7.1 12.1
IPL [Member] | Other [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 10.8 12.3
WPL [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 250.1 250.2
WPL [Member] | Cost of removal obligations [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 142.3 142.2
WPL [Member] | Electric transmission cost recovery [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 56.8 36.3
WPL [Member] | Commodity cost recovery [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 11.6 13.0
WPL [Member] | Energy efficiency cost recovery [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 19.6 20.5
WPL [Member] | Derivatives [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 4.3 19.4
WPL [Member] | Other [Member]    
Regulatory Liabilities [Line Items]    
Regulatory liabilities $ 15.5 $ 18.8