Regulatory Matters (Duke Energy Indiana Narrative) (Details) - Duke Energy Indiana - Indiana Rate Case 2019 - Indiana Utility Regulatory Commission - USD ($) $ in Millions	Jul. 28, 2021	Jun. 29, 2020	Dec. 04, 2019	Jul. 02, 2019	Dec. 31, 2020
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease)				$ 395
Requested rate increase (decrease), percentage, net of tax			15.60%
Requested rate increase (decrease), amended, amount			$ 396
Approved rate increase (decrease) amount by state commission		$ 146
Disclosure of rate matters, rate base					$ 10,200
Public utilities, disclosure of rate matters, reduction of rate base		$ 200
Public utilities, disclosure of rate matters, rate base reduction due to depreciation methodology, percent		50.00%
Public utilities, disclosure of rate matters, rate base reduction due to approved return on equity, percent		20.00%
Approved return on equity, percentage	9.70%	9.70%
Requested return on equity, percentage		10.40%
Public utilities, disclosure of rate matters, rate base reduction due to earnings adjustments, percent		20.00%
Public utilities, approved return on equity, step one estimated percentage		75.00%
Public utilities, approved return on equity, step two estimated percentage		25.00%
Approved capital structure, percentage	54.00%