Regulatory Matters (Duke Energy Indiana Narrative) (Details) - Duke Energy Indiana - Indiana Rate Case 2019 - Indiana Utility Regulatory Commission - USD ($) $ in Millions	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
Public utilities, approved rate increase (decrease)	5.70%
Approved return on equity, percentage	9.70%
Approved capital structure, percentage	53.00%
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%
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%