Asset Retirement Obligations (NDTF Information) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Asset Retirement Obligations [Line Items]
Legally restricted NDTF investments, fair value	$ 6,102	$ 5,579
Duke Energy Carolinas [Member]
Asset Retirement Obligations [Line Items]
Legally restricted NDTF investments, fair value	3,443	3,133
Duke Energy Progress [Member]
Asset Retirement Obligations [Line Items]
Legally restricted NDTF investments, fair value	2,659	2,446
Progress Energy [Member]
Asset Retirement Obligations [Line Items]
Legally restricted NDTF investments, fair value	$ 2,659	$ 2,446