Debt and Credit Facilities (Schedule of Line of Credit Facilities) (Details) - USD ($)	Dec. 31, 2017	Mar. 31, 2017	Feb. 28, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Tax exempt bonds	$ (941,000,000)			$ (1,053,000,000)
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	8,000,000,000	$ 8,000,000,000	$ 7,500,000,000.0
Commercial Paper	(1,799,000,000)
Outstanding letters of credit	(63,000,000)
Tax exempt bonds	(81,000,000)
Coal ash set-aside	(500,000,000)
Available capacity	5,557,000,000
Parent Company [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	2,850,000,000
Commercial Paper	(561,000,000)
Outstanding letters of credit	(54,000,000)
Available capacity	2,235,000,000
Duke Energy Carolinas [Member]
Line of Credit Facility [Line Items]
Tax exempt bonds	(243,000,000)			(355,000,000)
Duke Energy Carolinas [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	1,350,000,000
Commercial Paper	(371,000,000)
Outstanding letters of credit	(4,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	725,000,000
Duke Energy Progress [Member]
Line of Credit Facility [Line Items]
Tax exempt bonds	(48,000,000)			(48,000,000)
Duke Energy Progress [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	1,250,000,000
Commercial Paper	(314,000,000)
Outstanding letters of credit	(2,000,000)
Coal ash set-aside	(250,000,000)
Available capacity	684,000,000
Duke Energy Florida [Member] | Revolving Credit Facility [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]
Tax exempt bonds	(77,000,000)			(77,000,000)
Duke Energy Ohio [Member] | Revolving Credit Facility [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]
Tax exempt bonds	(572,000,000)			$ (572,000,000)
Duke Energy Indiana [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	600,000,000
Commercial Paper	(260,000,000)
Tax exempt bonds	(81,000,000)
Available capacity	259,000,000
Piedmont Natural Gas [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Size	700,000,000		$ 850,000,000
Commercial Paper	(248,000,000)
Outstanding letters of credit	(2,000,000)
Available capacity	450,000,000
Proceeds Loaned To Subsidiary Registrants [Member] | Parent Company [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Commercial Paper	$ (625,000,000)