Regulatory Matters (Regulatory Matters Narrative - Duke Energy Florida) (Details) - Duke Energy Florida $ in Millions	Jul. 01, 2020 USD ($) plant MW	Sep. 30, 2020 USD ($)	May 19, 2020 USD ($)	Apr. 02, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 19, 2019 USD ($)	Nov. 22, 2019 USD ($)	Apr. 30, 2019 USD ($)
FPSC
Public Utilities, General Disclosures [Line Items]
Accelerated fuel cost refund				$ 78
Number of solar plants | plant	10
Generation capacity (MW) | MW	750
Hurricane Michael storm damage
Public Utilities, General Disclosures [Line Items]
Estimated storm costs - capital and operation maintenance		$ 119			$ 204
Hurricane Michael storm damage | FPSC
Public Utilities, General Disclosures [Line Items]
Estimated storm costs - capital and operation maintenance								$ 223
Amount of recovery costs sought			$ 188				$ 191
Requested supplemental true-up			$ 3
Hurricane Dorian storm damage
Public Utilities, General Disclosures [Line Items]
Estimated storm costs - capital and operation maintenance		38			$ 167
Hurricane Dorian storm damage | FPSC
Public Utilities, General Disclosures [Line Items]
Estimated storm costs - capital and operation maintenance						$ 169
Actual storm costs - capital and operation maintenance		$ 145
Solar Project
Public Utilities, General Disclosures [Line Items]
Estimated cost of facilities	$ 1,000
Estimated cost of facilities period	4 years