Income Taxes (Deferred Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		$ 245	$ 188
Capital lease obligations		63	63
Pension, postretirement and other employee benefits		580	546
Progress Energy merger purchase accounting adjustments		1,009	1,124
Tax credits and NOL carryforwards		3,719	3,540
Other		206
Valuation allowance		(160)	(184)
Total deferred income tax assets		5,662	5,277
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(1,584)	(1,625)
Accelerated depreciation rates		(13,070)	(11,715)
Regulatory assets and deferred debits, net		(3,633)	(3,694)
Other			(44)
Total deferred income tax liabilities		(18,287)	(17,078)
Net deferred income tax liabilities		(12,625)	(11,801)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		3,719	3,540
Valuation allowance		(160)	(184)
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Current Assets: Other			1,593
Investments and Other Assets: Other		80	29
Deferred Credits and Other Liabilities: Other		(12,705)	(13,423)
Net deferred income tax liabilities		(12,625)	(11,801)
State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Net reduction in deferred tax liability		95		$ 145
Investment Tax Credits [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		864
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		$ 864
Investment Tax Credits [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year		Dec. 31, 2029
Investment Tax Credits [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year		Dec. 31, 2035
Alternative Minimum Tax Credit [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		$ 1,121
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		1,121
NOL Carryforwards [Member] | Federal [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		484
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		$ 484
NOL Carryforwards [Member] | Federal [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year		Dec. 31, 2030
NOL Carryforwards [Member] | Federal [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year		Dec. 31, 2033
NOL Carryforwards [Member] | State [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		$ 299
Valuation allowance		(81)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		299
Valuation allowance		$ (81)
NOL Carryforwards [Member] | State [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year		Dec. 31, 2016
NOL Carryforwards [Member] | State [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year		Dec. 31, 2035
NOL Carryforwards [Member] | Foreign Jurisdictions [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		$ 100
Valuation allowance		(79)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		100
Valuation allowance		$ (79)
NOL Carryforwards [Member] | Foreign Jurisdictions [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year		Dec. 31, 2026
NOL Carryforwards [Member] | Foreign Jurisdictions [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year		Dec. 31, 2034
Foreign Tax Credit [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		$ 851
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		$ 851
Foreign Tax Credit [Member] | Foreign Jurisdictions [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year		Dec. 31, 2024
Duke Energy Carolinas [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		$ 38	53
Capital lease obligations		9	10
Pension, postretirement and other employee benefits		46	4
Tax credits and NOL carryforwards		170	157
Other		20	12
Total deferred income tax assets		283	236
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(1,057)	(1,051)
Accelerated depreciation rates		(4,429)	(4,046)
Regulatory assets and deferred debits, net		(943)	(953)
Total deferred income tax liabilities		(6,429)	(6,050)
Net deferred income tax liabilities		(6,146)	(5,814)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		170	157
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Current Assets: Other			3
Current Liabilities: Other			(5)
Deferred Credits and Other Liabilities: Other		(6,146)	(5,812)
Net deferred income tax liabilities		(6,146)	(5,814)
Progress Energy [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		115	108
Pension, postretirement and other employee benefits		186	188
Tax credits and NOL carryforwards		997	980
Other		48
Valuation allowance		(38)	(13)
Total deferred income tax assets		1,308	1,263
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(412)	(427)
Accelerated depreciation rates		(4,169)	(3,284)
Regulatory assets and deferred debits, net		(1,517)	(1,602)
Other			(151)
Total deferred income tax liabilities		(6,098)	(5,464)
Net deferred income tax liabilities		(4,790)	(4,201)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		997	980
Valuation allowance		(38)	(13)
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Current Assets: Other			558
Deferred Credits and Other Liabilities: Other		(4,790)	(4,759)
Net deferred income tax liabilities		(4,790)	(4,201)
Duke Energy Progress [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		25	28
Pension, postretirement and other employee benefits		92	96
Tax credits and NOL carryforwards		163	91
Other		2	55
Valuation allowance			(1)
Total deferred income tax assets		282	269
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(228)	(232)
Accelerated depreciation rates		(2,325)	(2,030)
Regulatory assets and deferred debits, net		(756)	(809)
Total deferred income tax liabilities		(3,309)	(3,071)
Net deferred income tax liabilities		(3,027)	(2,802)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		163	91
Valuation allowance			(1)
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Current Assets: Other			106
Deferred Credits and Other Liabilities: Other		(3,027)	(2,908)
Net deferred income tax liabilities		(3,027)	(2,802)
Duke Energy Florida [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		66	78
Pension, postretirement and other employee benefits		82	93
Tax credits and NOL carryforwards		177	252
Other		46
Total deferred income tax assets		371	423
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(201)	(245)
Accelerated depreciation rates		(1,868)	(1,252)
Regulatory assets and deferred debits, net		(762)	(792)
Other			(246)
Total deferred income tax liabilities		(2,831)	(2,535)
Net deferred income tax liabilities		(2,460)	(2,112)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		177	252
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Current Assets: Other			340
Deferred Credits and Other Liabilities: Other		(2,460)	(2,452)
Net deferred income tax liabilities		(2,460)	(2,112)
Duke Energy Ohio [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		29	(8)
Pension, postretirement and other employee benefits		24	17
Tax credits and NOL carryforwards		25	38
Investments and other assets		3	14
Other		37	35
Total deferred income tax assets		118	96
Deferred Tax Liabilities, Gross [Abstract]
Accelerated depreciation rates		(1,356)	(1,660)
Regulatory assets and deferred debits, net		(169)	(141)
Total deferred income tax liabilities		(1,525)	(1,801)
Net deferred income tax liabilities		(1,407)	(1,705)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		25	38
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Current Assets: Other			60
Deferred Credits and Other Liabilities: Other		(1,407)	(1,765)
Net deferred income tax liabilities		(1,407)	(1,705)
Duke Energy Indiana [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		5	12
Capital lease obligations		2	2
Pension, postretirement and other employee benefits		40	43
Tax credits and NOL carryforwards		215	260
Other		20	11
Total deferred income tax assets		282	328
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(7)	(4)
Accelerated depreciation rates		(1,797)	(1,603)
Regulatory assets and deferred debits, net		(135)	(106)
Total deferred income tax liabilities		(1,939)	(1,713)
Net deferred income tax liabilities		(1,657)	(1,385)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		215	260
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Current Assets: Other			206
Deferred Credits and Other Liabilities: Other		(1,657)	(1,591)
Net deferred income tax liabilities		$ (1,657)	$ (1,385)
2013 [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate				6.90%
2013 [Member] | Duke Energy Carolinas [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate				6.90%
2013 [Member] | Duke Energy Progress [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate				6.90%
January 2014 [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate			6.00%
January 2014 [Member] | Duke Energy Carolinas [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate			6.00%
January 2014 [Member] | Duke Energy Progress [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate			6.00%
January 2015 [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate		5.00%
January 2015 [Member] | Duke Energy Carolinas [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate		5.00%
January 2015 [Member] | Duke Energy Progress [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate		5.00%
Scenario, Forecast [Member] | January 2016 [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate	4.00%
Scenario, Forecast [Member] | January 2016 [Member] | Duke Energy Carolinas [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate	4.00%
Scenario, Forecast [Member] | January 2016 [Member] | Duke Energy Progress [Member] | State [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate	4.00%