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Asset Retirement Obligations (Tables)
12 Months Ended
Dec. 31, 2011
Asset Retirement Obligations [Abstract]  
Change in asset retirement obligations
          
 
Great Plains Energy
KCP&L
 
2011
2010
2011
2010
 
(millions)
Beginning balance
$143.3 $132.6 $129.7 $119.8 
Additions
 0.8  2.0  -  2.0 
Revision in timing and/or estimates
 (3.8) -  (3.8) - 
Accretion
 9.3  8.7  8.4  7.9 
Ending balance
$149.6 $143.3 $134.3 $129.7