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Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Employee Savings Plans [Abstract]    
Employer contributions $ 52 $ 49
Duke Energy Carolinas [Member]    
Employee Savings Plans [Abstract]    
Employer contributions 18 16
Progress Energy [Member]    
Employee Savings Plans [Abstract]    
Employer contributions 15 14
Duke Energy Progress [Member]    
Employee Savings Plans [Abstract]    
Employer contributions 11 11
Duke Energy Florida [Member]    
Employee Savings Plans [Abstract]    
Employer contributions 4 4
Duke Energy Ohio [Member]    
Employee Savings Plans [Abstract]    
Employer contributions 1 1
Duke Energy Indiana [Member]    
Employee Savings Plans [Abstract]    
Employer contributions $ 2 $ 2