Debt and Credit Facilities (Schedule of Line of Credit Facilities) (Details) - Revolving Credit Facility [Member] - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Facility size	$ 8,000,000,000	$ 7,500,000,000.0
Commercial paper	(3,115,000,000)
Outstanding letters of credit	(68,000,000)
Tax exempt bonds	(81,000,000)
Coal ash set-aside	(500,000,000)
Available capacity	4,236,000,000
Parent Company [Member]
Line of Credit Facility [Line Items]
Facility size	3,150,000,000
Commercial paper	(1,392,000,000)
Outstanding letters of credit	(59,000,000)
Available capacity	1,699,000,000
Duke Energy Carolinas [Member]
Line of Credit Facility [Line Items]
Facility size	1,350,000,000
Commercial paper	(732,000,000)
Outstanding letters of credit	(4,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	364,000,000
Duke Energy Progress [Member]
Line of Credit Facility [Line Items]
Facility size	1,250,000,000
Commercial paper	(661,000,000)
Outstanding letters of credit	(2,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	337,000,000
Duke Energy Florida [Member]
Line of Credit Facility [Line Items]
Facility size	700,000,000
Outstanding letters of credit	(1,000,000)
Available capacity	699,000,000
Duke Energy Ohio [Member]
Line of Credit Facility [Line Items]
Facility size	450,000,000
Commercial paper	(45,000,000)
Available capacity	405,000,000
Duke Energy Indiana [Member]
Line of Credit Facility [Line Items]
Facility size	600,000,000
Commercial paper	(150,000,000)
Tax exempt bonds	(81,000,000)
Available capacity	369,000,000
Piedmont Natural Gas [Member]
Line of Credit Facility [Line Items]
Facility size	500,000,000	$ 850,000,000
Commercial paper	(135,000,000)
Outstanding letters of credit	(2,000,000)
Available capacity	363,000,000
Proceeds Loaned To Subsidiary Registrants [Member] | Parent Company [Member]
Line of Credit Facility [Line Items]
Commercial paper	$ (625,000,000)