Debt and Credit Facilities (Schedule of Line of Credit Facilities) (Details) - Revolving Credit Facility [Member]	Mar. 31, 2018 USD ($)
Line of Credit Facility [Line Items]
Facility size	$ 8,000,000,000
Commercial paper	(2,602,000,000)
Outstanding letters of credit	(59,000,000)
Tax exempt bonds	(81,000,000)
Coal ash set-aside	(500,000,000)
Available capacity	4,758,000,000
Parent Company [Member]
Line of Credit Facility [Line Items]
Facility size	2,650,000,000
Commercial paper	(1,281,000,000)
Outstanding letters of credit	(50,000,000)
Available capacity	1,319,000,000
Duke Energy Carolinas [Member]
Line of Credit Facility [Line Items]
Facility size	1,550,000,000
Commercial paper	(340,000,000)
Outstanding letters of credit	(4,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	956,000,000
Duke Energy Progress [Member]
Line of Credit Facility [Line Items]
Facility size	1,250,000,000
Commercial paper	(464,000,000)
Outstanding letters of credit	(2,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	534,000,000
Duke Energy Florida [Member]
Line of Credit Facility [Line Items]
Facility size	800,000,000
Outstanding letters of credit	(1,000,000)
Available capacity	799,000,000
Duke Energy Ohio [Member]
Line of Credit Facility [Line Items]
Facility size	450,000,000
Commercial paper	(140,000,000)
Available capacity	310,000,000
Duke Energy Indiana [Member]
Line of Credit Facility [Line Items]
Facility size	600,000,000
Commercial paper	(282,000,000)
Tax exempt bonds	(81,000,000)
Available capacity	237,000,000
Piedmont Natural Gas [Member]
Line of Credit Facility [Line Items]
Facility size	700,000,000
Commercial paper	(95,000,000)
Outstanding letters of credit	(2,000,000)
Available capacity	603,000,000
Proceeds Loaned To Subsidiary Registrants [Member] | Parent Company [Member]
Line of Credit Facility [Line Items]
Commercial paper	$ (625,000,000)