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Regulatory Matters (Narrative) (Details)	3 Months Ended			9 Months Ended		12 Months Ended
Regulatory Matters (Narrative) (Details)	Mar. 31, 2017 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) MW	Sep. 30, 2014 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Public Utilities, General Disclosures [Line Items]
Electric Domestic Regulated Revenue		$ (6,017,000,000)	$ (5,861,000,000)	$ (16,564,000,000)	$ (16,549,000,000)
Regulatory assets, noncurrent		11,290,000,000		11,290,000,000			$ 11,042,000,000
Impairment charges		111,000,000	1,000,000	111,000,000	81,000,000
Other Nonoperating Income (Expense)		(57,000,000)	(109,000,000)	(203,000,000)	(293,000,000)
Payments to Acquire Businesses, Gross				1,317,000,000	16,000,000
Property, Plant and Equipment, Net		73,776,000,000		73,776,000,000			70,046,000,000
Payments to Acquire Property, Plant, and Equipment				4,642,000,000	3,755,000,000
Other liabilities		1,595,000,000		1,595,000,000			1,675,000,000
Accounts Payable, Current		$ 2,078,000,000		$ 2,078,000,000			2,271,000,000
Atlantic Coast Pipeline (ACP) [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage		40.00%		40.00%
Atlantic Coast Pipeline (ACP) [Member] \| Dominion Resources [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage		45.00%		45.00%
Atlantic Coast Pipeline (ACP) [Member] \| Piedmont Natural Gas [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage		10.00%		10.00%
Sabal Trail Transmission Pipeline [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage		7.50%		7.50%
Sabal Trail Transmission Pipeline [Member] \| Spectra Energy [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage		59.50%		59.50%
Sabal Trail Transmission Pipeline [Member] \| NextEra [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage		33.00%		33.00%
Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) \| MW				1,541
Property, Plant and Equipment, Net		$ 207,000,000		$ 207,000,000
Duke Energy Carolinas [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent		2,741,000,000		2,741,000,000			2,465,000,000
Impairment charges					3,000,000
Other Nonoperating Income (Expense)		(42,000,000)	(44,000,000)	(125,000,000)	(137,000,000)
Property, Plant and Equipment, Net		25,208,000,000		25,208,000,000			24,672,000,000
Payments to Acquire Property, Plant, and Equipment				1,372,000,000	1,289,000,000
Other liabilities		618,000,000		618,000,000			642,000,000
Accounts Payable, Current		623,000,000		623,000,000			709,000,000
Duke Energy Carolinas [Member] \| William States Lee Combined Cycle Facility [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost of new utility plant, including AFUDC		$ 600,000,000		$ 600,000,000
Duke Energy Carolinas [Member] \| William States Lee Combined Cycle Facility [Member] \| NCEMC [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage		13.00%		13.00%
Duke Energy Carolinas [Member] \| Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Property, Plant and Equipment, Net		$ 110,000,000		$ 110,000,000
Duke Energy Progress [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent		2,816,000,000		2,816,000,000			2,675,000,000
Impairment charges					(18,000,000)
Other Nonoperating Income (Expense)		(14,000,000)	(18,000,000)	(49,000,000)	(34,000,000)
Payments to Acquire Businesses, Gross				1,249,000,000
Property, Plant and Equipment, Net		17,172,000,000		17,172,000,000			15,186,000,000
Payments to Acquire Property, Plant, and Equipment				1,120,000,000	871,000,000
Other liabilities		120,000,000		120,000,000			168,000,000
Accounts Payable, Current		381,000,000		381,000,000			481,000,000
Duke Energy Progress [Member] \| Western Carolinas Modernization Plan [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost		1,100,000,000		$ 1,100,000,000
Duke Energy Progress [Member] \| Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) \| MW				376
Property, Plant and Equipment, Net		460,000,000		$ 460,000,000
Duke Energy Florida [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent		2,719,000,000		2,719,000,000			2,733,000,000
Impairment charges		7,000,000	1,000,000	7,000,000	2,000,000
Other Nonoperating Income (Expense)		(2,000,000)	(6,000,000)	(12,000,000)	(17,000,000)
Property, Plant and Equipment, Net		10,363,000,000		10,363,000,000			9,955,000,000
Payments to Acquire Property, Plant, and Equipment				696,000,000	513,000,000
Other liabilities		157,000,000		157,000,000			158,000,000
Accounts Payable, Current		316,000,000		$ 316,000,000			365,000,000
Duke Energy Florida [Member] \| Scenario, Forecast [Member]
Public Utilities, General Disclosures [Line Items]
Payments to Acquire Businesses, Gross	$ 166,000,000
Duke Energy Florida [Member] \| FERC Transmission Rates [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Return on Equity, Percentage				10.00%
Approved return on equity percentage amount by state commission				10.80%
Customer Refund Liability, Noncurrent		14,100,000		$ 14,100,000
Duke Energy Florida [Member] \| FERC Complaint 3 [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission				8.69%
Duke Energy Florida [Member] \| Citrus County Station [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost of new utility plant, including AFUDC		1,500,000,000		$ 1,500,000,000
Duke Energy Florida [Member] \| Suwannee Station [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost of new utility plant, including AFUDC		197,000,000		197,000,000
Duke Energy Florida [Member] \| Crystal River Unit 3 [Member] \| 2013 FPSC Settlement Agreement[Member] \| FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Impairment charges		15,000,000
Duke Energy Florida [Member] \| Crystal River Unit 3 [Member] \| 2013 FPSC Settlement Agreement[Member] \| FPSC [Member] \| Scenario, Forecast [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Regulatory Costs Not yet Approved						$ 1,298,000,000
Regulatory assets, noncurrent						1,283,000,000
Approved rate increase amount by state commission						168,000,000
Duke Energy Florida [Member] \| Crystal River Unit 3 [Member] \| Crystal River Unit 3 Requested Financing Order [Member] \| FPSC [Member] \| Scenario, Forecast [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount						$ 93,000,000
Duke Energy Florida [Member] \| Levy Nuclear Station [Member] \| FPSC [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent		54,000,000		54,000,000
Approved rate increase amount by state commission				$ 0
Duke Energy Florida [Member] \| Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) \| MW				873
Property, Plant and Equipment, Net		121,000,000		$ 121,000,000
Duke Energy Ohio [Member]
Public Utilities, General Disclosures [Line Items]
Electric Domestic Regulated Revenue		(367,000,000)	(352,000,000)	(1,005,000,000)	(998,000,000)
Regulatory assets, noncurrent		495,000,000		495,000,000			512,000,000
Impairment charges					94,000,000
Other Nonoperating Income (Expense)			(3,000,000)	2,000,000	(9,000,000)
Property, Plant and Equipment, Net		5,175,000,000		5,175,000,000			4,937,000,000
Payments to Acquire Property, Plant, and Equipment				266,000,000	242,000,000
Other liabilities		165,000,000		165,000,000			166,000,000
Accounts Payable, Current		$ 219,000,000		219,000,000			209,000,000
Duke Energy Ohio [Member] \| EE and Peak Demand Reduction Program [Member] \| PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Electric Domestic Regulated Revenue				$ 23,000,000
Duke Energy Ohio [Member] \| Natural Gas Rate Case [Member] \| PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission				9.84%
Duke Energy Ohio [Member] \| MGP Remediation [Member] \| PUCO [Member]
Public Utilities, General Disclosures [Line Items]
Approved rate increase amount by state commission				$ 56,000,000
Duke Energy Ohio [Member] \| FERC Complaint 1 [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission				11.38%
Duke Energy Ohio [Member] \| FERC Transmission Rates [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission				12.38%
Percentage Recovered Through Future Rate Case				30.00%
Duke Energy Ohio [Member] \| RTO Realignment [Member]
Public Utilities, General Disclosures [Line Items]
Approved MVP Proposals		17		17
MISO estimate of Duke Energy Ohio's MVP obligation				$ 2,700,000,000
Duke Energy Ohio [Member] \| East Bend Station [Member] \| Dayton Power and Light [Member]
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage		31.00%		31.00%
Payments to Acquire Property, Plant, and Equipment				$ 12,400,000
Duke Energy Ohio [Member] \| Regional Transmission Organization [Member]
Public Utilities, General Disclosures [Line Items]
Restructuring Reserve		$ 91,000,000		91,000,000
Regulatory assets, noncurrent		72,000,000		72,000,000
Duke Energy Indiana [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent		645,000,000		645,000,000			685,000,000
Impairment charges		85,000,000		85,000,000
Other Nonoperating Income (Expense)			$ (5,000,000)	(9,000,000)	(16,000,000)
Property, Plant and Equipment, Net		9,340,000,000		9,340,000,000			8,815,000,000
Payments to Acquire Property, Plant, and Equipment				506,000,000	$ 462,000,000
Other liabilities		107,000,000		107,000,000			90,000,000
Accounts Payable, Current		149,000,000		$ 149,000,000			$ 179,000,000
Duke Energy Indiana [Member] \| FERC Transmission Rates [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission				12.38%
Duke Energy Indiana [Member] \| FERC Transmission Rates [Member] \| Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission				0.50%
Duke Energy Indiana [Member] \| FERC Complaint 2 [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity percentage amount by state commission				8.67%
Duke Energy Indiana [Member] \| Grid Infrastructure Improvement Plan [Member]
Public Utilities, General Disclosures [Line Items]
Estimated capital cost		1,900,000,000		$ 1,900,000,000
Duke Energy Indiana [Member] \| Edwardsport Igcc Plant [Member] \| IGCC Rider Proceeding [Member] \| IURC [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount				(7,000,000)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount				78,000,000
Legal Fees				5,000,000
Impairment charges				85,000,000
Other Nonoperating Income (Expense)				5,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets		78,000,000		78,000,000
Other liabilities		7,000,000		7,000,000
Accounts Payable, Current		5,000,000		$ 5,000,000
Regulatory Asset, Amortization Period				8 years
Regulatory Assets		108,000,000		$ 108,000,000
Duke Energy Indiana [Member] \| Generation Facilities To Be Retired [Member]
Public Utilities, General Disclosures [Line Items]
Capacity (in MW) \| MW				668
Property, Plant and Equipment, Net		$ 86,000,000		$ 86,000,000