Related Party Transactions (Other Revenue and Expense) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Duke Energy Carolinas [Member] | Corporate governance and shared service expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 214	$ 206	$ 647	$ 645
Duke Energy Carolinas [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	6	5	17	17
Duke Energy Carolinas [Member] | JDA [Member] | Duke Energy Progress [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	13	9	66	42
Related party transaction, expenses from transactions with related party	61	39	134	91
Duke Energy Carolinas [Member] | Intercompany natural gas transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	3	3	11	5
Progress Energy [Member] | Corporate governance and shared service expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	216	207	613	555
Progress Energy [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	8	10	25	29
Progress Energy [Member] | JDA [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	61	39	134	91
Related party transaction, expenses from transactions with related party	13	9	66	42
Progress Energy [Member] | Intercompany natural gas transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	20	19	58	57
Duke Energy Progress [Member] | Corporate governance and shared service expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	138	112	382	321
Duke Energy Progress [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	3	4	9	11
Duke Energy Progress [Member] | JDA [Member] | Duke Energy Carolinas [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	61	39	134	91
Related party transaction, expenses from transactions with related party	13	9	66	42
Duke Energy Progress [Member] | Intercompany natural gas transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	20	19	58	57
Duke Energy Florida [Member] | Corporate governance and shared service expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	78	95	231	234
Duke Energy Florida [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	5	6	16	18
Duke Energy Ohio [Member] | Corporate governance and shared service expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	85	90	264	275
Duke Energy Ohio [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	1	1	3	3
Duke Energy Indiana [Member] | Corporate governance and shared service expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	105	94	302	281
Duke Energy Indiana [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	2	2	6	6
Piedmont Natural Gas [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party				62
Piedmont Natural Gas [Member] | Corporate governance and shared service expenses [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	39	11	115	25
Piedmont Natural Gas [Member] | Indemnification coverages [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	1	1	2	$ 2
Piedmont Natural Gas [Member] | Intercompany natural gas transactions [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	$ 23	$ 22	$ 69