Debt and Credit Facilities (Summary of Debt Issuances) (Details) $ in Millions	Mar. 31, 2016 USD ($)
Debt Instrument [Line Items]
Debt issuances	$ 1,000
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Debt issuances	$ 1,000
First Mortgage [Member] | March 2016 2.500% First Mortgage Bond Maturing March 2023 [Member]
Debt Instrument [Line Items]
Interest rate	2.50%
Debt issuances	$ 500
First Mortgage [Member] | March 2016 3.875% First Mortgage Bond Maturing March 2046 [Member]
Debt Instrument [Line Items]
Interest rate	3.875%
Debt issuances	$ 500
First Mortgage [Member] | Duke Energy Carolinas [Member] | March 2016 2.500% First Mortgage Bond Maturing March 2023 [Member]
Debt Instrument [Line Items]
Interest rate	2.50%
Debt issuances	$ 500
First Mortgage [Member] | Duke Energy Carolinas [Member] | March 2016 3.875% First Mortgage Bond Maturing March 2046 [Member]
Debt Instrument [Line Items]
Interest rate	3.875%
Debt issuances	$ 500