Related Party Transactions (Intercompany Income Taxes) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	$ 109	$ 163
Intercompany income tax payable	250	247
Progress Energy [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	2	106
Intercompany income tax payable	316	348
Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	6	5
Intercompany income tax payable	244	227
Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	2	5
Intercompany income tax payable	77	125
Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	88	129
Intercompany income tax payable	64	63
Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	88	114
Intercompany income tax payable	75	74
Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	7	7
Intercompany income tax payable	3	8
Income Taxes [Member] | Affiliated Entity [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	19	1
Income Taxes [Member] | Affiliated Entity [Member] | Progress Energy [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	139
Intercompany income tax payable		37
Income Taxes [Member] | Affiliated Entity [Member] | Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	47
Intercompany income tax payable		90
Income Taxes [Member] | Affiliated Entity [Member] | Duke Energy Florida [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	48	37
Income Taxes [Member] | Affiliated Entity [Member] | Duke Energy Ohio [Member]
Related Party Transaction [Line Items]
Intercompany income tax receivable	8
Intercompany income tax payable		1
Income Taxes [Member] | Affiliated Entity [Member] | Duke Energy Indiana [Member]
Related Party Transaction [Line Items]
Intercompany income tax payable	23	3
Income Taxes [Member] | Affiliated Entity [Member] | Piedmont Natural Gas [Member]
Related Party Transaction [Line Items]
Intercompany income tax payable	$ 44	$ 38