Investments in Debt and Equity Securities (Tables)

3 Months Ended

Mar. 31, 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.

	March 31, 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	$	—	$	—	$	201	$	—	$	—	$	179
Equity securities	1,823		64		3,592		1,823		58		3,590
Corporate debt securities	16		3		454		7		8		432
Municipal bonds	6		—		211		5		1		185
U.S. government bonds	33		—		1,288		11		5		1,254
Other debt securities	1		4		148		—		4		177
Total NDTF	$	1,879	$	71	$	5,894	$	1,846	$	76	$	5,817
Other Investments
Cash and cash equivalents	$	—	$	—	$	29	$	—	$	—	$	29
Equity securities	33		1		97		32		1		95
Corporate debt securities	1		2		91		1		3		92
Municipal bonds	3		1		76		3		1		74
U.S. government bonds	2		—		56		—		—		45
Other debt securities	—		2		55		—		2		62
Total Other Investments(a)	$	39	$	6	$	404	$	36	$	7	$	397
Total Investments	$	1,918	$	77	$	6,298	$	1,882	$	83	$	6,214

(a)    These amounts are recorded in Other with 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)	March 31, 2016
Due in one year or less	$	136
Due after one through five years	769
Due after five through 10 years	559
Due after 10 years	915
Total	$	2,379

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
	March 31,
(in millions)	2016		2015
Realized gains	$	54	$	102
Realized losses	50		14

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.

	March 31, 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	$	—	$	—	$	50	$	—	$	—	$	34
Equity securities	1,022		31		2,088		1,021		27		2,094
Corporate debt securities	8		2		257		3		5		292
Municipal bonds	1		—		53		1		—		33
U.S. government bonds	12		—		502		3		3		438
Other debt securities	1		4		138		—		4		147
Total NDTF	$	1,044	$	37	$	3,088	$	1,028	$	39	$	3,038
Other Investments
Other debt securities	$	—	$	1	$	3	$	—	$	1	$	3
Total Other Investments(a)	$	—	$	1	$	3	$	—	$	1	$	3
Total Investments	$	1,044	$	38	$	3,091	$	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)	March 31, 2016
Due in one year or less	$	14
Due after one through five years	195
Due after five through 10 years	224
Due after 10 years	520
Total	$	953

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
	March 31,
(in millions)	2016		2015
Realized gains	$	34	$	90
Realized losses	37		12

Progress Energy [Member]

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

Available-for-sale Securities

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

	March 31, 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	$	—	$	—	$	145
Equity securities	801		33		1,504		802		31		1,496
Corporate debt securities	8		1		197		4		3		140
Municipal bonds	5		—		158		4		1		152
U.S. government bonds	21		—		786		8		2		816
Other debt securities	—		—		10		—		—		30
Total NDTF	$	835	$	34	$	2,806	$	818	$	37	$	2,779
Other Investments
Cash and cash equivalents	$	—	$	—	$	17	$	—	$	—	$	18
Municipal bonds	3		—		46		3		—		45
Total Other Investments(a)	$	3	$	—	$	63	$	3	$	—	$	63
Total Investments	$	838	$	34	$	2,869	$	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)	March 31, 2016
Due in one year or less	$	101
Due after one through five years	486
Due after five through 10 years	264
Due after 10 years	346
Total	$	1,197

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
	March 31,
(in millions)	2016		2015
Realized gains	$	19	$	12
Realized losses	13		1

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.

	March 31, 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	$	—	$	—	$	100	$	—	$	—	$	110
Equity securities	595		27		1,184		596		25		1,178
Corporate debt securities	6		1		145		3		2		96
Municipal bonds	5		—		158		4		1		150
U.S. government bonds	15		—		479		6		2		486
Other debt securities	—		—		6		—		—		18
Total NDTF	$	621	$	28	$	2,072	$	609	$	30	$	2,038
Other Investments
Cash and cash equivalents	$	—	$	—	$	1	$	—	$	—	$	1
Total Other Investments(a)	$	—	$	—	$	1	$	—	$	—	$	1
Total Investments	$	621	$	28	$	2,073	$	609	$	30	$	2,039

(a)    These amounts are recorded in Other with 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)	March 31, 2016
Due in one year or less	$	37
Due after one through five years	282
Due after five through 10 years	219
Due after 10 years	250
Total	$	788

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
	March 31,
(in millions)	2016		2015
Realized gains	$	15	$	9
Realized losses	11		1

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.

	March 31, 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	$	—	$	—	$	51	$	—	$	—	$	35
Equity securities	206		6		320		206		6		318
Corporate debt securities	2		—		52		1		1		44
Municipal bonds	—		—		—		—		—		2
U.S. government bonds	6		—		307		2		—		330
Other debt securities	—		—		4		—		—		12
Total NDTF (c)	$	214	$	6	$	734	$	209	$	7	$	741
Other Investments
Cash and cash equivalents	$	—	$	—	$	1	$	—	$	—	$	6
Municipal bonds	3		—		46		3		—		45
Total Other Investments(a)	$	3	$	—	$	47	$	3	$	—	$	51
Total Investments	$	217	$	6	$	781	$	212	$	7	$	792

(a)    These amounts are recorded in Other with 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 March 31, 2016, is primarily due to reimbursements from the NDTF for Duke Energy Florida's cost related to ongoing decommissioning activity of the Crystal River Unit 3 Nuclear Plant.

Investments Classified by Contractual Maturity Date

The table below summarizes the maturity date for debt securities.

(in millions)	March 31, 2016
Due in one year or less	$	64
Due after one through five years	204
Due after five through 10 years	45
Due after 10 years	96
Total	$	409

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
	March 31,
(in millions)	2016		2015
Realized gains	$	4	$	3
Realized losses	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.

	March 31, 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	$	—	$	—	$	1	$	—	$	—	$	2
Equity securities	27		—		72		27		—		71
Corporate debt securities	—		—		2		—		—		2
Municipal bonds	—		1		27		—		1		26
Total Other Investments(a)	$	27	$	1	$	102	$	27	$	1	$	101
Total Investments	$	27	$	1	$	102	$	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)	March 31, 2016
Due in one year or less	$	2
Due after one through five years	14
Due after five through 10 years	9
Due after 10 years	4
Total	$	29