Derivatives and Hedging (Schedule of Offsetting Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Offsetting Assets [Line Items]
Gross amounts recognized	$ 51	$ 162
Net amounts presented on Balance Sheets	51	162
Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	35	111
Gross amounts offset		(11)
Net amounts presented on Balance Sheets	35	100
Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	16	51
Gross amounts offset		(2)
Net amounts presented on Balance Sheets	16	49
Duke Energy Carolinas [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	33
Net amounts presented on Balance Sheets	2	33
Duke Energy Carolinas [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	23
Net amounts presented on Balance Sheets	2	23
Duke Energy Carolinas [Member] | Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized		10
Gross amounts offset		(1)
Net amounts presented on Balance Sheets		9
Progress Energy [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	3	85
Net amounts presented on Balance Sheets	3	85
Progress Energy [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	64
Gross amounts offset		(11)
Net amounts presented on Balance Sheets	2	53
Progress Energy [Member] | Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	21
Gross amounts offset		(1)
Net amounts presented on Balance Sheets	1	20
Duke Energy Progress [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	46
Net amounts presented on Balance Sheets	2	46
Duke Energy Progress [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	36
Net amounts presented on Balance Sheets	1	36
Duke Energy Progress [Member] | Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	10
Gross amounts offset		(1)
Net amounts presented on Balance Sheets	1	9
Duke Energy Florida [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	39
Net amounts presented on Balance Sheets	1	39
Duke Energy Florida [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	28
Gross amounts offset		(11)
Net amounts presented on Balance Sheets	1	17
Duke Energy Florida [Member] | Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized		11
Net amounts presented on Balance Sheets		11
Duke Energy Ohio [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	5
Net amounts presented on Balance Sheets	1	5
Duke Energy Ohio [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	1	4
Net amounts presented on Balance Sheets	1	4
Duke Energy Ohio [Member] | Other Noncurrent Assets [Member]
Offsetting Assets [Line Items]
Gross amounts recognized		1
Net amounts presented on Balance Sheets		1
Duke Energy Indiana [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	27	16
Net amounts presented on Balance Sheets	27	16
Duke Energy Indiana [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	27	16
Net amounts presented on Balance Sheets	27	16
Piedmont Natural Gas [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	3
Net amounts presented on Balance Sheets	2	3
Piedmont Natural Gas [Member] | Current Assets, Other [Member]
Offsetting Assets [Line Items]
Gross amounts recognized	2	3
Net amounts presented on Balance Sheets	$ 2	$ 3