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Segment Information - Schedule of Segment Information (Parenthetical) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Segment Reporting Information [Line Items]        
Internally allocated interest costs, pre tax rate     6.00%  
Capital structure assumption, debt to equity ratio     50.00%  
TECO Guatemala [Member]
       
Segment Reporting Information [Line Items]        
Revenues $ 0 $ 31.5 $ 0 $ 100.4