XML 115 R66.htm IDEA: XBRL DOCUMENT v2.4.0.8
Nuclear Plant (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Investments in decommissioning trust fund [Line Items]      
Cost Basis $ 138.1 $ 130.4  
Gross Unrealized Gains 47.1 26.0  
Gross Unrealized Losses (1.3) (1.7)  
Fair Value, Nuclear decommissioning trust fund 183.9 154.7 135.3
Weighted average maturity of debt securities (in years) 7    
Realized Gains on investments in decommissioning trust fund 2.4 1.7 1.0
Realized Losses on investments in decommissioning trust fund (0.7) (0.7) (0.7)
Equity Securities [Member]
     
Investments in decommissioning trust fund [Line Items]      
Cost Basis 83.7 80.6  
Gross Unrealized Gains 44.6 21.1  
Gross Unrealized Losses (0.6) (1.6)  
Fair Value, Nuclear decommissioning trust fund 127.7 100.1  
Debt Securities [Member]
     
Investments in decommissioning trust fund [Line Items]      
Cost Basis 51.0 46.6  
Gross Unrealized Gains 2.5 4.9  
Gross Unrealized Losses (0.7) (0.1)  
Fair Value, Nuclear decommissioning trust fund 52.8 51.4  
Other Securities [Member]
     
Investments in decommissioning trust fund [Line Items]      
Cost Basis 3.4 3.2  
Gross Unrealized Gains 0 0  
Gross Unrealized Losses 0 0  
Fair Value, Nuclear decommissioning trust fund 3.4 3.2  
Kansas City Power and Light Company [Member]
     
Investments in decommissioning trust fund [Line Items]      
Fair Value, Nuclear decommissioning trust fund $ 183.9 $ 154.7 $ 135.3