Related Party Transactions (Other Revenue and Expense) (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	12 Months Ended
	Oct. 31, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Duke Energy Carolinas [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			$ 858	$ 831		$ 914
Duke Energy Carolinas [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			23	22		24
Duke Energy Carolinas [Member] | Joint Dispatch Agreement (JDA) [Member] | Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party			49	38		51
Related party transaction, expenses from transactions with related party			145	156		183
Duke Energy Carolinas [Member] | Intercompany Natural Gas Transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			9	2
Progress Energy [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			736	710		712
Progress Energy [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			38	35		38
Progress Energy [Member] | Joint Dispatch Agreement (JDA) [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party			145	156		183
Related party transaction, expenses from transactions with related party			49	38		51
Progress Energy [Member] | Intercompany Natural Gas Transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			77	19
Duke Energy Progress [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			438	397		403
Duke Energy Progress [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			15	14		16
Duke Energy Progress [Member] | Joint Dispatch Agreement (JDA) [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party			145	156		183
Related party transaction, expenses from transactions with related party			49	38		51
Duke Energy Progress [Member] | Intercompany Natural Gas Transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			77	19
Duke Energy Florida [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			298	313		309
Duke Energy Florida [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			23	21		22
Duke Energy Ohio [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			363	356		342
Duke Energy Ohio [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			5	5		6
Duke Energy Indiana [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			370	366		349
Duke Energy Indiana [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			8	$ 8		$ 9
Piedmont Natural Gas [Member] | Corporate Governance And Shared Service Expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			50
Piedmont Natural Gas [Member] | Indemnification Coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party			2
Piedmont Natural Gas [Member] | Intercompany Natural Gas Transactions [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	$ 7	$ 14			$ 74		$ 83
Piedmont Natural Gas [Member] | Intercompany Natural Gas Transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party			$ 86