Variable Interest Entities (Schedule of Non-Consolidated VIEs) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,366	$ 925
Other noncurrent assets	2,792	2,769
Taxes accrued	627	384
Current Liabilities: Other	1,734	2,044
Deferred income taxes	15,058	14,155
Noncurrent Liabilities: Other	1,624	1,753
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	1,106	751
Other noncurrent assets	18	12
Total assets	1,124	763
Current Liabilities: Other	3	3
Deferred income taxes	29
Noncurrent Liabilities: Other	12	13
Total liabilities	44	16
Net assets	1,080	747
Pipeline Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	895	487
Other noncurrent assets	18	12
Total assets	913	499
Deferred income taxes	29
Total liabilities	29
Net assets	884	499
Renewables [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	172	174
Total assets	172	174
Net assets	172	174
Other VIEs [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates	39	90
Total assets	39	90
Current Liabilities: Other	3	3
Noncurrent Liabilities: Other	12	13
Total liabilities	15	16
Net assets	24	74
Duke Energy Ohio [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	81	129
Other noncurrent assets	27	23
Taxes accrued	157	178
Current Liabilities: Other	74	91
Deferred income taxes	1,512	1,443
Noncurrent Liabilities: Other	134	166
Duke Energy Ohio [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	46	82
Total assets	46	82
Net assets	46	82
Duke Energy Indiana [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	83	114
Other noncurrent assets	170	147
Taxes accrued	146	31
Current Liabilities: Other	111	93
Deferred income taxes	1,979	1,900
Noncurrent Liabilities: Other	65	27
Duke Energy Indiana [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	75	101
Total assets	75	101
Net assets	75	101
Piedmont Natural Gas [Member]
Variable Interest Entities [Line Items]
Receivables from affiliated companies	8	7
Investments in equity method unconsolidated affiliates	76	212
Other noncurrent assets	11	21
Taxes accrued	30	67
Current Liabilities: Other	72	102
Deferred income taxes	1,046	931
Noncurrent Liabilities: Other	$ 141	189
Piedmont Natural Gas [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Investments in equity method unconsolidated affiliates		139
Total assets		139
Noncurrent Liabilities: Other		4
Total liabilities		4
Net assets		$ 135