Debt and Credit Facilities (Schedule of Line of Credit Facilities) (Details) (Revolving Credit Facility [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2015
Line of Credit Facility [Line Items]
Facility size	$ 7,500
Commercial paper	(3,256)
Outstanding letters of credit	(66)
Tax exempt bonds	(116)
Available capacity	4,062
Parent Company [Member]
Line of Credit Facility [Line Items]
Facility size	3,200
Commercial paper	(2,764)
Outstanding letters of credit	(60)
Available capacity	376
Parent Company [Member] | Proceeds Loaned To Subsidiary Registrants [Member]
Line of Credit Facility [Line Items]
Commercial paper	(475)
Duke Energy Carolinas [Member]
Line of Credit Facility [Line Items]
Facility size	1,200
Commercial paper	(300)
Outstanding letters of credit	(4)
Tax exempt bonds	(35)
Available capacity	861
Duke Energy Progress [Member]
Line of Credit Facility [Line Items]
Facility size	1,000
Outstanding letters of credit	(1)
Available capacity	999
Duke Energy Florida [Member]
Line of Credit Facility [Line Items]
Facility size	900
Commercial paper	(17)
Outstanding letters of credit	(1)
Available capacity	882
Duke Energy Ohio [Member]
Line of Credit Facility [Line Items]
Facility size	600
Commercial paper	(25)
Available capacity	575
Duke Energy Indiana [Member]
Line of Credit Facility [Line Items]
Facility size	600
Commercial paper	(150)
Tax exempt bonds	(81)
Available capacity	$ 369