Regulatory Matters (Duke Energy Ohio - Exit Obligation Rollforward) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Restructuring Reserve [Roll Forward]
Balance, beginning of period	$ 11
Cash reductions	(8)
Balance, end of period	39
Regulatory assets	14,637	$ 14,062
Duke Energy Ohio
Restructuring Reserve [Roll Forward]
Regulatory assets	707	649
RTO Realignment | Duke Energy Ohio
Restructuring Reserve [Roll Forward]
Balance, beginning of period	50
Cash reductions	(4)
Balance, end of period	46
Regulatory assets	$ 33	$ 37