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Fair Value Measurements (Reconciliation of Assets and Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance $ 4 $ 33
Total pretax gains (losses) included in earnings 21 (7)
Purchases 24 50
Sales (1) (15)
Settlements (37) (54)
Transfers in and/or out of level 3   6
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers out of Level 3   6
Total gains (losses) included on the Consolidated Balance Sheet as regulatory asset or liability 4 (9)
Ending balance 15 4
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Beginning balance (1) 13
Total pretax gains (losses) included in earnings 21 (7)
Purchases 24 50
Sales 1  
Settlements 37 54
Total Gains (losses) included on the Consolidated Balance Sheet as regulatory asset or liability 4 (9)
Ending balance 10 (1)
Pretax amounts included in the Consolidated Statements of Comprehensive Income related to Level 3 measurements outstanding at end of period   (14)
Investments [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 5 20
Sales   (15)
Ending balance 5 5
Derivative [Member]    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Pretax amounts included in the Consolidated Statements of Comprehensive Income related to Level 3 measurements outstanding at end of period   (14)
Duke Energy Carolinas [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 3 1
Settlements   (2)
Ending balance   3
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Beginning balance   (2)
Settlements   (2)
Duke Energy Carolinas [Member] | Investments [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 3 3
Ending balance   3
Duke Energy Ohio [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers out of Level 3   6
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Beginning balance (18) (4)
Total pretax gains (losses) included in earnings 21 (9)
Purchases 5 1
Settlements 5 13
Total Gains (losses) included on the Consolidated Balance Sheet as regulatory asset or liability 0 1
Ending balance 3 (18)
Duke Energy Indiana [Member]    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Beginning balance 14 12
Total pretax gains (losses) included in earnings   3
Purchases 19 49
Settlements (30) (41)
Total Gains (losses) included on the Consolidated Balance Sheet as regulatory asset or liability 4 (9)
Ending balance $ 7 $ 14