Investments in Debt and Equity Securities (Tables)

9 Months Ended

Sep. 30, 2016

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

Available-for-sale Securities

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

	September 30, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized		Estimated		Unrealized		Unrealized		Estimated
	Holding		Holding		Fair		Holding		Holding		Fair
(in millions)	Gains		Losses(b)		Value		Gains		Losses(b)		Value
NDTF
Cash and cash equivalents	$	—	$	—	$	151	$	—	$	—	$	179
Equity securities	1,968		55		3,949		1,823		58		3,590
Corporate debt securities	25		2		551		7		8		432
Municipal bonds	9		1		341		5		1		185
U.S. government bonds	31		—		994		11		5		1,254
Other debt securities	—		3		132		—		4		177
Total NDTF	$	2,033	$	61	$	6,118	$	1,846	$	76	$	5,817
Other Investments
Cash and cash equivalents	$	—	$	—	$	24	$	—	$	—	$	29
Equity securities	38		—		104		32		1		95
Corporate debt securities	2		1		91		1		3		92
Municipal bonds	5		1		78		3		1		74
U.S. government bonds	1		—		49		—		—		45
Other debt securities	—		1		55		—		2		62
Total Other Investments(a)	$	46	$	3	$	401	$	36	$	7	$	397
Total Investments	$	2,079	$	64	$	6,519	$	1,882	$	83	$	6,214

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

(b) Substantially all these amounts are considered other-than-temporary impairments on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	September 30, 2016
Due in one year or less	$	92
Due after one through five years	655
Due after five through 10 years	529
Due after 10 years	1,015
Total	$	2,291

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.

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
(in millions)	2016		2015		2016		2015
Realized gains	$	82	$	30	$	200	$	160
Realized losses	42		28		134		59

Duke Energy Carolinas [Member]

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

Available-for-sale Securities

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

	September 30, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized		Estimated		Unrealized		Unrealized		Estimated
	Holding		Holding		Fair		Holding		Holding		Fair
(in millions)	Gains		Losses(b)		Value		Gains		Losses(b)		Value
NDTF
Cash and cash equivalents	$	—	$	—	$	43	$	—	$	—	$	34
Equity securities	1,091		29		2,170		1,021		27		2,094
Corporate debt securities	14		2		374		3		5		292
Municipal bonds	2		—		66		1		—		33
U.S. government bonds	12		—		454		3		3		438
Other debt securities	—		3		123		—		4		147
Total NDTF	$	1,119	$	34	$	3,230	$	1,028	$	39	$	3,038
Other Investments
Other debt securities	$	—	$	1	$	3	$	—	$	1	$	3
Total Other Investments(a)	$	—	$	1	$	3	$	—	$	1	$	3
Total Investments	$	1,119	$	35	$	3,233	$	1,028	$	40	$	3,041

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

(b) Substantially all these amounts represent other-than-temporary impairments on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	September 30, 2016
Due in one year or less	$	3
Due after one through five years	206
Due after five through 10 years	268
Due after 10 years	543
Total	$	1,020

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.

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
(in millions)	2016		2015		2016		2015
Realized gains	$	58	$	25	$	125	$	132
Realized losses	28		24		84		47

Progress Energy [Member]

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

Available-for-sale Securities

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

	September 30, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized		Estimated		Unrealized		Unrealized		Estimated
	Holding		Holding		Fair		Holding		Holding		Fair
(in millions)	Gains		Losses(b)		Value		Gains		Losses(b)		Value
NDTF
Cash and cash equivalents	$	—	$	—	$	108	$	—	$	—	$	145
Equity securities	877		26		1,779		802		31		1,496
Corporate debt securities	11		—		177		4		3		140
Municipal bonds	7		1		275		4		1		152
U.S. government bonds	19		—		540		8		2		816
Other debt securities	—		—		9		—		—		30
Total NDTF	$	914	$	27	$	2,888	$	818	$	37	$	2,779
Other Investments
Cash and cash equivalents	$	—	$	—	$	20	$	—	$	—	$	18
Municipal bonds	4		—		47		3		—		45
Total Other Investments(a)	$	4	$	—	$	67	$	3	$	—	$	63
Total Investments	$	918	$	27	$	2,955	$	821	$	37	$	2,842

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

(b) Substantially all these amounts represent other-than-temporary impairments on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	September 30, 2016
Due in one year or less	$	67
Due after one through five years	372
Due after five through 10 years	187
Due after 10 years	422
Total	$	1,048

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.

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
(in millions)	2016		2015		2016		2015
Realized gains	$	21	$	5	$	71	$	26
Realized losses	13		4		49		10

Duke Energy Progress [Member]

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

Available-for-sale Securities

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

	September 30, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized		Estimated		Unrealized		Unrealized		Estimated
	Holding		Holding		Fair		Holding		Holding		Fair
(in millions)	Gains		Losses(b)		Value		Gains		Losses(b)		Value
NDTF
Cash and cash equivalents	$	—	$	—	$	56	$	—	$	—	$	110
Equity securities	657		21		1,438		596		25		1,178
Corporate debt securities	8		—		123		3		2		96
Municipal bonds	7		1		275		4		1		150
U.S. government bonds	12		—		279		6		2		486
Other debt securities	—		—		6		—		—		18
Total NDTF	$	684	$	22	$	2,177	$	609	$	30	$	2,038
Other Investments
Cash and cash equivalents	$	—	$	—	$	1	$	—	$	—	$	1
Total Other Investments(a)	$	—	$	—	$	1	$	—	$	—	$	1
Total Investments	$	684	$	22	$	2,178	$	609	$	30	$	2,039

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

(b) Substantially all these amounts represent other-than-temporary impairments on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	September 30, 2016
Due in one year or less	$	21
Due after one through five years	200
Due after five through 10 years	142
Due after 10 years	320
Total	$	683

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.

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
(in millions)	2016		2015		2016		2015
Realized gains	$	18	$	4	$	60	$	21
Realized losses	11		3		42		8

Duke Energy Florida [Member]

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

Available-for-sale Securities

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

	September 30, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized		Estimated		Unrealized		Unrealized		Estimated
	Holding		Holding		Fair		Holding		Holding		Fair
(in millions)	Gains		Losses(b)		Value		Gains		Losses(b)		Value
NDTF
Cash and cash equivalents	$	—	$	—	$	52	$	—	$	—	$	35
Equity securities	220		5		341		206		6		318
Corporate debt securities	3		—		54		1		1		44
Municipal bonds	—		—		—		—		—		2
U.S. government bonds	7		—		261		2		—		330
Other debt securities	—		—		3		—		—		12
Total NDTF (c)	$	230	$	5	$	711	$	209	$	7	$	741
Other Investments
Cash and cash equivalents	$	—	$	—	$	2	$	—	$	—	$	6
Municipal bonds	4		—		47		3		—		45
Total Other Investments(a)	$	4	$	—	$	49	$	3	$	—	$	51
Total Investments	$	234	$	5	$	760	$	212	$	7	$	792

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

(b) Substantially all these amounts represent other-than-temporary impairments on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

(c) The decrease in estimated fair value of the NDTF as of September 30, 2016, is due to reimbursements from the NDTF for costs related to ongoing decommissioning activity of the Crystal Unit 3 Nuclear Plant.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	September 30, 2016
Due in one year or less	$	46
Due after one through five years	172
Due after five through 10 years	45
Due after 10 years	102
Total	$	365

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.

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
(in millions)	2016		2015		2016		2015
Realized gains	$	3	$	1	$	11	$	5
Realized losses	2		1		7		2

Duke Energy Indiana [Member]

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

Available-for-sale Securities

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

	September 30, 2016						December 31, 2015
	Gross		Gross				Gross		Gross
	Unrealized		Unrealized		Estimated		Unrealized		Unrealized		Estimated
	Holding		Holding		Fair		Holding		Holding		Fair
(in millions)	Gains		Losses(b)		Value		Gains		Losses(b)		Value
Other Investments
Cash and cash equivalents	$	—	$	—	$	—	$	—	$	—	$	2
Equity securities	31		—		77		27		—		71
Corporate debt securities	—		—		2		—		—		2
Municipal bonds	1		1		28		—		1		26
Total Other Investments(a)	$	32	$	1	$	107	$	27	$	1	$	101
Total Investments	$	32	$	1	$	107	$	27	$	1	$	101

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

(b) Substantially all these amounts represent other-than-temporary impairments on investments within Investment Trusts that have been recognized immediately as a regulatory asset.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	September 30, 2016
Due in one year or less	$	3
Due after one through five years	9
Due after five through 10 years	13
Due after 10 years	5
Total	$	30