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Asset Retirement Obligations (Rollforward) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Asset Retirement Obligation [Line Items]    
Beginning Balance $ 10,175 $ 10,611
Accretion expense 427 435
Liabilities settled (638) (619)
Liabilities incurred in the current year 39 51
Revisions in estimates of cash flows 464 (303)
Ending Balance 10,467 10,175
Duke Energy Carolinas [Member]    
Asset Retirement Obligation [Line Items]    
Beginning Balance 3,610 3,895
Accretion expense 179 184
Liabilities settled (281) (282)
Liabilities incurred in the current year 8 5
Revisions in estimates of cash flows 433 (192)
Ending Balance 3,949 3,610
Progress Energy [Member]    
Asset Retirement Obligation [Line Items]    
Beginning Balance 5,414 5,475
Accretion expense 225 228
Liabilities settled (272) (270)
Liabilities incurred in the current year 5  
Revisions in estimates of cash flows 39 (19)
Ending Balance 5,411 5,414
Duke Energy Progress [Member]    
Asset Retirement Obligation [Line Items]    
Beginning Balance 4,673 4,697
Accretion expense 196 195
Liabilities settled (227) (204)
Revisions in estimates of cash flows 178 (15)
Ending Balance 4,820 4,673
Duke Energy Florida [Member]    
Asset Retirement Obligation [Line Items]    
Beginning Balance 742 778
Accretion expense 29 33
Liabilities settled (45) (65)
Liabilities incurred in the current year 5  
Revisions in estimates of cash flows (140) (4)
Ending Balance 591 742
Duke Energy Ohio [Member]    
Asset Retirement Obligation [Line Items]    
Beginning Balance 84 77
Accretion expense 4 3
Liabilities settled (5) (7)
Liabilities incurred in the current year   7
Revisions in estimates of cash flows 10 4
Ending Balance 93 84
Duke Energy Indiana [Member]    
Asset Retirement Obligation [Line Items]    
Beginning Balance 781 866
Accretion expense 29 32
Liabilities settled (79) (49)
Liabilities incurred in the current year 25 29
Revisions in estimates of cash flows (34) (97)
Ending Balance 722 781
Piedmont Natural Gas [Member]    
Asset Retirement Obligation [Line Items]    
Beginning Balance 15 14
Accretion expense 1 1
Liabilities settled   (8)
Liabilities incurred in the current year   8
Revisions in estimates of cash flows 3  
Ending Balance $ 19 $ 15