Summary of Significant Accounting Policies (Expected Reserve for Credit Losses) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total pretax impact to Retained Earnings	$ 49,184	$ 47,951	$ 43,834	$ 41,737
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total pretax impact to Retained Earnings	2,471	4,108	3,113	3,013
Cumulative Effect, Period of Adoption, Adjustment | Revision of Prior Period, Accounting Standards Update, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total pretax impact to Retained Earnings	120
Duke Energy Carolinas | Cumulative Effect, Period of Adoption, Adjustment | Revision of Prior Period, Accounting Standards Update, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total pretax impact to Retained Earnings	16
Progress Energy
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total pretax impact to Retained Earnings	16,241	15,593	14,257	13,465
Progress Energy | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total pretax impact to Retained Earnings	7,109	$ 6,465	$ 5,131	$ 4,350
Progress Energy | Cumulative Effect, Period of Adoption, Adjustment | Revision of Prior Period, Accounting Standards Update, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total pretax impact to Retained Earnings	2
Duke Energy Progress | Cumulative Effect, Period of Adoption, Adjustment | Revision of Prior Period, Accounting Standards Update, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total pretax impact to Retained Earnings	1
Duke Energy Florida | Cumulative Effect, Period of Adoption, Adjustment | Revision of Prior Period, Accounting Standards Update, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total pretax impact to Retained Earnings	1
Piedmont | Cumulative Effect, Period of Adoption, Adjustment | Revision of Prior Period, Accounting Standards Update, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total pretax impact to Retained Earnings	$ 1