XML 46 R36.htm IDEA: XBRL DOCUMENT v3.8.0.1
Regulated Operations (Details) - USD ($)
$ in Millions
Mar. 31, 2018
Dec. 31, 2017
Schedule of Regulatory Assets and Liabilities [Line Items]    
Fuel clause over recoveries $ 49.9 $ 1.7
Current Regulatory Assets 31.6 40.8
Non-Current Regulatory Assets 275.6 283.0
Current Regulatory Liabilities 52.0 3.9
Non-Current Regulatory Liabilities 1,292.7 1,283.4
Other (B)    
Schedule of Regulatory Assets and Liabilities [Line Items]    
Current Regulatory Liabilities [1] 2.1 2.2
Non-Current Regulatory Liabilities 7.3 7.2
Income taxes recoverable from customers, net    
Schedule of Regulatory Assets and Liabilities [Line Items]    
Non-Current Regulatory Liabilities 951.3 955.5
Accrued removal obligations, net    
Schedule of Regulatory Assets and Liabilities [Line Items]    
Non-Current Regulatory Liabilities 295.7 288.4
Pension tracker    
Schedule of Regulatory Assets and Liabilities [Line Items]    
Non-Current Regulatory Liabilities 38.4 32.3
Oklahoma demand program rider under recovery (A)    
Schedule of Regulatory Assets and Liabilities [Line Items]    
Current Regulatory Assets [2] 23.9 31.6
SPP cost tracker under recovery (A)    
Schedule of Regulatory Assets and Liabilities [Line Items]    
Current Regulatory Assets [2] 6.9 7.7
Benefit obligations regulatory asset    
Schedule of Regulatory Assets and Liabilities [Line Items]    
Non-Current Regulatory Assets 174.6 177.2
Deferred storm expenses    
Schedule of Regulatory Assets and Liabilities [Line Items]    
Non-Current Regulatory Assets 39.7 42.2
Smart Grid    
Schedule of Regulatory Assets and Liabilities [Line Items]    
Non-Current Regulatory Assets 31.0 32.8
Unamortized loss on reacquired debt    
Schedule of Regulatory Assets and Liabilities [Line Items]    
Non-Current Regulatory Assets 12.1 12.3
Other Regulatory Asset [Member]    
Schedule of Regulatory Assets and Liabilities [Line Items]    
Current Regulatory Assets [2] 0.8 1.5
Non-Current Regulatory Assets $ 18.2 $ 18.5
[1] Included in Other Current Liabilities on the Condensed Consolidated Balance Sheets.
[2] Included in Other Current Assets on the Condensed Consolidated Balance Sheets.