Related Party Transactions (Intercompany Income Taxes) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	$ 85	$ 163
Intercompany income tax payable	127	247
Progress Energy [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	3	106
Intercompany income tax payable	208	348
Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	5	5
Intercompany income tax payable	169	227
Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	1	5
Intercompany income tax payable	42	125
Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	74	129
Intercompany income tax payable	47	63
Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	87	114
Intercompany income tax payable	50	74
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	8	7
Intercompany income tax payable	50	8
Income Taxes [Member] | Affiliated Entity [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable		1
Intercompany income tax payable	20
Income Taxes [Member] | Affiliated Entity [Member] | Progress Energy [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	102
Intercompany income tax payable		37
Income Taxes [Member] | Affiliated Entity [Member] | Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	35
Intercompany income tax payable		90
Income Taxes [Member] | Affiliated Entity [Member] | Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable		37
Intercompany income tax payable	3
Income Taxes [Member] | Affiliated Entity [Member] | Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	19
Intercompany income tax payable		1
Income Taxes [Member] | Affiliated Entity [Member] | Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	25
Intercompany income tax payable		3
Income Taxes [Member] | Affiliated Entity [Member] | Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	$ 56
Intercompany income tax payable		$ 38