Derivatives and Hedging (Schedule of Offsetting Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Offsetting Liabilities [Line Items]
Gross amounts recognized	$ 230	$ 252
Net amounts presented on Balance Sheets	230	252
Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	66	52
Gross amounts offset	(3)	(11)
Net amounts presented on Balance Sheets	63	41
Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	164	200
Gross amounts offset	(1)	(2)
Net amounts presented on Balance Sheets	163	198
Duke Energy Carolinas [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	35	16
Net amounts presented on Balance Sheets	35	16
Duke Energy Carolinas [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	31
Gross amounts offset	(2)
Net amounts presented on Balance Sheets	29
Duke Energy Carolinas [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	4	16
Gross amounts offset		(1)
Net amounts presented on Balance Sheets	4	15
Progress Energy [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	36	25
Net amounts presented on Balance Sheets	36	25
Progress Energy [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	19	12
Gross amounts offset	(2)	(11)
Net amounts presented on Balance Sheets	17	1
Progress Energy [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	17	13
Gross amounts offset	(1)	(1)
Net amounts presented on Balance Sheets	16	12
Duke Energy Progress [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	18	7
Net amounts presented on Balance Sheets	18	7
Duke Energy Progress [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	8
Gross amounts offset	(2)
Net amounts presented on Balance Sheets	6
Duke Energy Progress [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	10	7
Gross amounts offset	(1)	(1)
Net amounts presented on Balance Sheets	9	6
Duke Energy Florida [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	12	12
Net amounts presented on Balance Sheets	12	12
Duke Energy Florida [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	10	12
Gross amounts offset		(11)
Net amounts presented on Balance Sheets	10	1
Duke Energy Florida [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	2
Net amounts presented on Balance Sheets	2
Duke Energy Ohio [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	5	6
Net amounts presented on Balance Sheets	5	6
Duke Energy Ohio [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	1	1
Net amounts presented on Balance Sheets	1	1
Duke Energy Ohio [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	4	5
Net amounts presented on Balance Sheets	4	5
Duke Energy Indiana [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized		2
Net amounts presented on Balance Sheets		2
Duke Energy Indiana [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized		2
Net amounts presented on Balance Sheets		2
Piedmont Natural Gas [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	142	187
Net amounts presented on Balance Sheets	142	187
Piedmont Natural Gas [Member] | Other Current Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	11	35
Net amounts presented on Balance Sheets	11	35
Piedmont Natural Gas [Member] | Other Noncurrent Liabilities [Member]
Offsetting Liabilities [Line Items]
Gross amounts recognized	131	152
Net amounts presented on Balance Sheets	$ 131	$ 152