Related Party Transactions (Intercompany Income Taxes) (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Income tax payable	$ 22	$ 44
Progress Energy [Member]
Related Party Transaction [Line Items]
Income taxes receivable	273	168
Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Income tax payable	24	21
Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Income taxes receivable	140	44
Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Income taxes receivable		22
Income tax payable	3
Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Income tax payable	14	35
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Income taxes receivable	$ 12	$ 7

Carrying amount due within one year of the balance sheet date (or one operating cycle, if longer) from tax authorities as of the balance sheet date representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.5(c))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3(a)(4))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_IncomeTaxesReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant