Investments in Debt and Equity Securities (Tables)

12 Months Ended

Dec. 31, 2016

Schedule of Available-for-sale Securities [Line Items]

Available-For-Sale Investments

The following table presents the estimated fair value of investments in available-for-sale securities.

	December 31, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized				Unrealized		Unrealized
	Holding		Holding		Estimated		Holding		Holding		Estimated
(in millions)	Gains		Losses(a)		Fair Value		Gains		Losses(a)		Fair Value
NDTF
Cash and cash equivalents	$	—	$	—	$	111	$	—	$	—	$	179
Equity securities	2,092		54		4,106		1,823		58		3,590
Corporate debt securities	10		8		528		7		8		432
Municipal bonds	3		10		331		5		1		185
U.S. government bonds	10		8		984		11		5		1,254
Other debt securities	—		3		124		—		4		177
Total NDTF	$	2,115	$	83	$	6,184	$	1,846	$	76	$	5,817
Other Investments
Cash and cash equivalents	$	—	$	—	$	25	$	—	$	—	$	29
Equity securities	38		—		104		32		1		95
Corporate debt securities	1		1		66		1		3		92
Municipal bonds	2		1		82		3		1		74
U.S. government bonds	—		1		51		—		—		45
Other debt securities	—		2		42		—		2		62
Total Other Investments(b)	$	41	$	5	$	370	$	36	$	7	$	397
Total Investments	$	2,156	$	88	$	6,554	$	1,882	$	83	$	6,214

(a) Substantially all these amounts are considered OTTIs on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

(b)     These amounts are recorded in Other within Investments and Other Assets on the Consolidated Balance Sheets.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	December 31, 2016
Due in one year or less	$	94
Due after one through five years	653
Due after five through 10 years	515
Due after 10 years	946
Total	$	2,208

Schedule of Realized Gain (Loss)

Realized gains and losses, which were determined on a specific identification basis, from sales of available-for-sale securities were as follows.

	Years Ended December 31,
(in millions)	2016		2015		2014
Realized gains	$	246	$	193	$	271
Realized losses	187		98		105

Duke Energy Carolinas [Member]

Schedule of Available-for-sale Securities [Line Items]

Available-For-Sale Investments

The following table presents the estimated fair value of investments in available-for-sale securities.

	December 31, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized				Unrealized		Unrealized
	Holding		Holding		Estimated		Holding		Holding		Estimated
(in millions)	Gains		Losses(a)		Fair Value		Gains		Losses(a)		Fair Value
NDTF
Cash and cash equivalents	$	—	$	—	$	18	$	—	$	—	$	34
Equity securities	1,157		28		2,245		1,021		27		2,094
Corporate debt securities	5		6		354		3		5		292
Municipal bonds	1		2		67		1		—		33
U.S. government bonds	2		5		458		3		3		438
Other debt securities	—		3		116		—		4		147
Total NDTF	$	1,165	$	44	$	3,258	$	1,028	$	39	$	3,038
Other Investments
Other debt securities	$	—	$	1	$	3	$	—	$	1	$	3
Total Other Investments(b)	$	—	$	1	$	3	$	—	$	1	$	3
Total Investments	$	1,165	$	45	$	3,261	$	1,028	$	40	$	3,041

(a) Substantially all these amounts represent OTTIs on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

(b) These amounts are recorded in Other within Investments and Other Assets on the Consolidated Balance Sheets.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	December 31, 2016
Due in one year or less	$	3
Due after one through five years	230
Due after five through 10 years	260
Due after 10 years	505
Total	$	998

Schedule of Realized Gain (Loss)

Realized gains and losses, which were determined on a specific identification basis, from sales of available-for-sale securities were as follows.

	Years Ended December 31,
(in millions)	2016		2015		2014
Realized gains	$	157	$	158	$	109
Realized losses	121		83		93

Progress Energy [Member]

Schedule of Available-for-sale Securities [Line Items]

Available-For-Sale Investments

The following table presents the estimated fair value of investments in available-for-sale securities.

	December 31, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized				Unrealized		Unrealized
	Holding		Holding		Estimated		Holding		Holding		Estimated
(in millions)	Gains		Losses(a)		Fair Value		Gains		Losses(a)		Fair Value
NDTF
Cash and cash equivalents	$	—	$	—	$	93	$	—	$	—	$	145
Equity securities	935		26		1,861		802		31		1,496
Corporate debt securities	5		2		174		4		3		140
Municipal bonds	2		8		264		4		1		152
U.S. government bonds	8		3		526		8		2		816
Other debt securities	—		—		8		—		—		30
Total NDTF	$	950	$	39	$	2,926	$	818	$	37	$	2,779
Other Investments
Cash and cash equivalents	$	—	$	—	$	21	$	—	$	—	$	18
Municipal bonds	2		—		44		3		—		45
Total Other Investments(b)	$	2	$	—	$	65	$	3	$	—	$	63
Total Investments	$	952	$	39	$	2,991	$	821	$	37	$	2,842

(a) Substantially all these amounts represent OTTIs on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

(b) These amounts are recorded in Other within Investments and Other Assets on the Consolidated Balance Sheets.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	December 31, 2016
Due in one year or less	$	84
Due after one through five years	347
Due after five through 10 years	187
Due after 10 years	398
Total	$	1,016

Schedule of Realized Gain (Loss)

Realized gains and losses, which were determined on a specific identification basis, from sales of available-for-sale securities were as follows.

	Years Ended December 31,
(in millions)	2016		2015		2014
Realized gains	$	84	$	33	$	157
Realized losses	64		13		11

Duke Energy Progress [Member]

Schedule of Available-for-sale Securities [Line Items]

Available-For-Sale Investments

The following table presents the estimated fair value of investments in available-for-sale securities.

	December 31, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized				Unrealized		Unrealized
	Holding		Holding		Estimated		Holding		Holding		Estimated
(in millions)	Gains		Losses(a)		Fair Value		Gains		Losses(a)		Fair Value
NDTF
Cash and cash equivalents	$	—	$	—	$	45	$	—	$	—	$	110
Equity securities	704		21		1,505		596		25		1,178
Corporate debt securities	4		1		120		3		2		96
Municipal bonds	2		8		263		4		1		150
U.S. government bonds	5		2		275		6		2		486
Other debt securities	—		—		5		—		—		18
Total NDTF	$	715	$	32	$	2,213	$	609	$	30	$	2,038
Other Investments
Cash and cash equivalents	$	—	$	—	$	1	$	—	$	—	$	1
Total Other Investments(b)	$	—	$	—	$	1	$	—	$	—	$	1
Total Investments	$	715	$	32	$	2,214	$	609	$	30	$	2,039

(a) Substantially all these amounts are considered OTTIs on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

(b)     These amounts are recorded in Other within Investments and Other Assets on the Consolidated Balance Sheets.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	December 31, 2016
Due in one year or less	$	28
Due after one through five years	190
Due after five through 10 years	142
Due after 10 years	303
Total	$	663

Schedule of Realized Gain (Loss)

Realized gains and losses, which were determined on a specific identification basis, from sales of available-for-sale securities were as follows.

	Years Ended December 31,
(in millions)	2016		2015		2014
Realized gains	$	71	$	26	$	19
Realized losses	55		11		5

Duke Energy Florida [Member]

Schedule of Available-for-sale Securities [Line Items]

Available-For-Sale Investments

The following table presents the estimated fair value of investments in available-for-sale securities.

	December 31, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized				Unrealized		Unrealized
	Holding		Holding		Estimated		Holding		Holding		Estimated
(in millions)	Gains		Losses(a)		Fair Value		Gains		Losses(a)		Fair Value
NDTF
Cash and cash equivalents	$	—	$	—	$	48	$	—	$	—	$	35
Equity securities	231		5		356		206		6		318
Corporate debt securities	1		1		54		1		1		44
Municipal bonds	—		—		1		—		—		2
U.S. government bonds	3		1		251		2		—		330
Other debt securities	—		—		3		—		—		12
Total NDTF(b)	$	235	$	7	$	713	$	209	$	7	$	741
Other Investments
Cash and cash equivalents	$	—	$	—	$	4	$	—	$	—	$	6
Municipal bonds	2		—		44		3		—		45
Total Other Investments(c)	$	2	$	—	$	48	$	3	$	—	$	51
Total Investments	$	237	$	7	$	761	$	212	$	7	$	792

(a) Substantially all these amounts are considered OTTIs on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

(b) The decrease in estimated fair value of the NDTF as of December 31, 2016, is primarily due to reimbursements from the NDTF for costs related to ongoing decommissioning activity of Crystal River Unit 3.

(c)     These amounts are recorded in Other within Investments and Other Assets on the Consolidated Balance Sheets.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	December 31, 2016
Due in one year or less	$	56
Due after one through five years	157
Due after five through 10 years	45
Due after 10 years	95
Total	$	353

Schedule of Realized Gain (Loss)

Realized gains and losses, which were determined on a specific identification basis, from sales of available-for-sale securities were as follows.

	Years Ended December 31,
(in millions)	2016		2015		2014
Realized gains	$	13	$	7	$	138
Realized losses	9		2		5

Duke Energy Indiana [Member]

Schedule of Available-for-sale Securities [Line Items]

Available-For-Sale Investments

The following table presents the estimated fair value of investments in available-for-sale securities.

	December 31, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized				Unrealized		Unrealized
	Holding		Holding		Estimated		Holding		Holding		Estimated
(in millions)	Gains		Losses(a)		Fair Value		Gains		Losses(a)		Fair Value
Other Investments
Cash and cash equivalents	$	—	$	—	$	—	$	—	$	—	$	2
Equity securities	33		—		79		27		—		71
Corporate debt securities	—		—		2		—		—		2
Municipal bonds	—		1		28		—		1		26
U.S. government bonds	—		—		1		—		—		—
Total Other Investments(b)	$	33	$	1	$	110	$	27	$	1	$	101
Total Investments	$	33	$	1	$	110	$	27	$	1	$	101

(a) Substantially all these amounts are considered OTTIs on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

(b)     These amounts are recorded in Other within Investments and Other Assets on the Consolidated Balance Sheets.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	December 31, 2016
Due in one year or less	$	3
Due after one through five years	13
Due after five through 10 years	9
Due after 10 years	6
Total	$	31