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Guarantees and Indemnifications(Narrative) (Details) - USD ($)
$ in Millions
Dec. 31, 2015
Dec. 31, 2014
Liabilities Recorded for Third Party Guarantees [Abstract]    
Face value of guarantees $ 21 $ 28
Surety Bond [Member]    
Guarantor Obligations [Line Items]    
Maximum potential amount of future payments associated with guarantees 47  
Standby Letters Of Credit [Member]    
Guarantor Obligations [Line Items]    
Maximum potential amount of future payments associated with guarantees 427  
Unused letters of credit 58  
Performance Guarantee [Member]    
Guarantor Obligations [Line Items]    
Maximum potential amount of future payments associated with guarantees 253  
Maximum potential of future amounts associated with guarantees with expiration dates 112  
Performance Guarantee [Member] | Less Than Wholly Owned Entity [Member]    
Guarantor Obligations [Line Items]    
Maximum potential amount of future payments associated with guarantees 15  
Spectra Capital [Member] | Performance Guarantee [Member]    
Guarantor Obligations [Line Items]    
Maximum potential amount of future payments associated with guarantees 205  
Progress Energy [Member]    
Liabilities Recorded for Third Party Guarantees [Abstract]    
Face value of guarantees 7 13
Progress Energy [Member] | Indemnification Agreement [Member]    
Guarantor Obligations [Line Items]    
Maximum potential amount of future payments associated with guarantees 97  
Maximum potential amount of future payments associated with guarantees with no expiration date 7  
Duke Energy Florida [Member]    
Liabilities Recorded for Third Party Guarantees [Abstract]    
Face value of guarantees $ 7 $ 7