Dyne Therapeutics 10-Q 7 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 21, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	DYNEGY INC.
Entity Central Index Key	1379895
Document Type	10-Q
Document Period End Date	31-Mar-15
Amendment Flag	FALSE
Current Fiscal Year End Date	-19
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		128,149,345
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Current Assets
Cash and cash equivalents	$1,734	$1,870
Restricted cash	205	113
Accounts receivable, net of allowance for doubtful accounts of $1 and $2, respectively	268	270
Inventory	224	208
Assets from risk management activities	80	78
Intangible assets	25	27
Prepayments and other current assets	121	108
Total Current Assets	2,657	2,674
Property, Plant and Equipment	3,698	3,685
Accumulated depreciation	-471	-430
Property, Plant and Equipment, Net	3,227	3,255
Other Assets
Restricted cash	5,100	5,100
Assets from risk management activities	4	2
Intangible assets	33	38
Deferred income taxes	32	20
Other long-term assets	162	143
Total Assets	11,215	11,232
Current Liabilities
Accounts payable	248	216
Accrued interest	184	80
Deferred income taxes	32	20
Intangible liabilities	39	45
Accrued liabilities and other current liabilities	198	157
Liabilities from risk management activities	111	132
Debt, current portion	8	31
Total Current Liabilities	820	681
Debt, long-term portion	7,077	7,075
Other Liabilities
Liabilities from risk management activities	36	31
Asset retirement obligations	211	205
Other long-term liabilities	236	217
Total Liabilities	8,380	8,209
Commitments and Contingencies (Note 9)
Stockholders’ Equity
Common stock, $0.01 par value, 420,000,000 shares authorized at March 31, 2015 and December 31, 2014; 124,667,804 shares and 124,436,941 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	1	1
Additional paid-in capital	3,332	3,338
Accumulated other comprehensive income, net of tax	19	20
Accumulated deficit	-916	-736
Total Dynegy Stockholders’ Equity	2,836	3,023
Noncontrolling interest	-1	0
Total Equity	2,835	3,023
Total Liabilities and Equity	11,215	11,232
Series A 5.375% mandatory convertible preferred stock
Stockholders’ Equity
Series A 5.375% mandatory convertible preferred stock, $0.01 par value; 4,000,000 shares issued and outstanding at March 31, 2015 and December 31, 2014	$400	$400

CONSOLIDATED_BALANCE_SHEETS_PA

CONSOLIDATED BALANCE SHEETS (PARENTHETICAL) (USD $)	3 Months Ended	12 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Allowance for doubtful accounts	$1	$2
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares authorized	420,000,000	420,000,000
Common stock, shares issued	124,667,804	124,436,941
Common stock, shares outstanding	124,667,804	124,436,941
Series A 5.375% mandatory convertible preferred stock
Preferred stock, par value (in dollars per share)	$0.01	$0.01
Preferred stock, series A 5.375%	5.38%	5.38%
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issues	4,000,000	4,000,000
Preferred stock, shares outstanding	4,000,000	4,000,000

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Income Statement [Abstract]
Revenues	$632		$762
Cost of sales, excluding depreciation expense	-377		-552
Gross margin	255		210
Operating and maintenance expense	-111		-110
Depreciation expense	-64		-67
General and administrative expense	-30		-26
Acquisition and integration costs	-90		-6
Operating income (loss)	-40		1
Interest expense	-136		-30
Other income and expense, net	-5		-6
Loss before income taxes	-181		-35
Income tax expense (Note 10)	0		-2
Net loss	-181		-37
Less: Net income attributable to noncontrolling interest	-1		4
Net loss attributable to Dynegy Inc.	-180		-41
Less: Dividends on preferred stock	5		0
Net loss attributable to Dynegy Inc. common stockholders	($185)		($41)
Loss Per Share (Note 12):
Basic and diluted loss per share attributable to Dynegy Inc. common stockholders	($1.49)		($0.41)
Basic and diluted shares outstanding	124	[1]	100
[1]	Entities with a net loss from continuing operations are prohibited from including potential common shares in the computation of diluted per share amounts. Accordingly, we have utilized the basic shares outstanding amount to calculate both basic and diluted loss per share for the three months ended March 31, 2015 and 2014.

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net loss	($181)	($37)
Other comprehensive loss before reclassifications:
Actuarial loss (net of tax of zero and zero, respectively)	0	-3
Amounts reclassified from accumulated other comprehensive income:
Amortization of unrecognized prior service cost (credit) and actuarial loss (gain) (net of tax of zero and zero, respectively)	-1	-1
Other comprehensive loss, net of tax	-1	-4
Comprehensive loss	-182	-41
Less: Comprehensive income (loss) attributable to noncontrolling interest	-1	3
Total comprehensive loss attributable to Dynegy Inc.	($181)	($44)

CONSOLIDATED_STATEMENTS_OF_COM1

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (PARENTHETICAL) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Tax on actuarial loss	$0	$0
Tax on amortization of unrecognized prior service cost (credit) and actuarial loss (gain)	$0	$0

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	($181)	($37)
Adjustments to reconcile net loss to net cash flows from operating activities:
Depreciation expense	64	67
Non-cash interest expense	7	5
Amortization of intangibles	-4	16
Risk management activities	-27	52
Deferred income taxes	0	2
Change in value of common stock warrants	5	6
Other	11	9
Changes in working capital:
Accounts receivable, net	1	23
Inventory	-18	0
Prepayments and other current assets	-10	-31
Accounts payable and accrued liabilities	83	55
Changes in non-current assets	-4	-2
Changes in non-current liabilities	18	1
Net cash provided by (used in) operating activities	-55	166
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	-40	-17
Net cash used in investing activities	-40	-17
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from long-term borrowings, net of financing costs	0	11
Repayments of borrowings	-25	-2
Dividends paid	-7	0
Interest rate swap settlement payments	-4	-4
Other financing	-5	-1
Net cash provided by (used) in financing activities	-41	4
Net increase (decrease) in cash and cash equivalents	-136	153
Cash and cash equivalents, beginning of period	1,870	843
Cash and cash equivalents, end of period	$1,734	$996

Basis_of_Presentation_and_Orga

Basis of Presentation and Organization	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Organization	Note 1—Basis of Presentation and Organization
	The accompanying unaudited consolidated financial statements have been prepared in accordance with the instructions to interim financial reporting as prescribed by the SEC. The year-end consolidated balance sheet data was derived from audited consolidated financial statements but does not include all disclosures required by the Generally Accepted Accounting Principles of the United States of America (“GAAP”).  The unaudited consolidated financial statements contained in this report include all material adjustments of a normal recurring nature that, in the opinion of management, are necessary for a fair presentation of the results for the interim periods. Certain prior period amounts in our consolidated financial statements have been reclassified to conform to current year presentation. These interim financial statements should be read together with the consolidated financial statements and notes thereto included in our annual report on Form 10-K for the year ended December 31, 2014, filed with the SEC on February 25, 2015, which we refer to as our “Form 10-K.” Unless the context indicates otherwise, throughout this report, the terms “Dynegy,” “the Company,” “we,” “us,” “our,” and “ours” are used to refer to Dynegy Inc. and its direct and indirect subsidiaries.
	Our current business operations are focused primarily on the unregulated power generation sector of the energy industry. We report the results of our power generation business as three segments in our unaudited consolidated financial statements: (i) the Coal segment (“Coal”), (ii) the IPH segment (“IPH”) and (iii) the Gas segment (“Gas”). Our consolidated financial results also reflect corporate-level expenses such as general and administrative expense, interest expense and income tax benefit (expense). All significant intercompany transactions have been eliminated. Please read Note 14—Segment Information for further discussion.
	IPH and its direct and indirect subsidiaries are organized into ring-fenced groups in order to maintain corporate separateness from Dynegy and its other subsidiaries. Certain of the entities in the IPH segment, including Illinois Power Generating Company (“Genco”), have an independent director whose consent is required for certain corporate actions, including material transactions with affiliates. Further, entities within the IPH segment present themselves to the public as separate entities.  They maintain separate books, records and bank accounts and separately appoint officers.  Furthermore, they pay liabilities from their own funds, conduct business in their own names and have restrictions on pledging their assets for the benefit of certain other persons.  These provisions restrict our ability to move cash out of these entities without meeting certain requirements as set forth in the governing documents.
	On April 1, 2015, we completed the acquisition of EquiPower Resources Corp. and Brayton Point Holdings, LLC from Energy Capital Partners for an aggregate base purchase price of approximately $3.35 billion in cash plus $100 million in common stock of Dynegy, subject to certain adjustments. On April 2, 2015, we completed the acquisition of Duke Energy’s commercial generation assets and retail business in the Midwest for a base purchase price of approximately $2.80 billion in cash, subject to certain adjustments. Please read Note 15—Subsequent Events for further discussion.
	Note 13—Condensed Consolidating Financial Information
	On May 20, 2013, Dynegy issued the Senior Notes, as further described in Note 8—Debt. On October 27, 2014, the Escrow Issuers, wholly-owned subsidiaries of Dynegy, issued the Notes as further described in Note 8—Debt. The 100 percent owned subsidiary guarantors, jointly, severally and unconditionally, guaranteed the payment obligations under the Senior Notes and Notes. Not all of Dynegy’s subsidiaries guarantee the Senior Notes and Notes including Dynegy’s indirect, wholly-owned subsidiary, IPH, which acquired AER and its subsidiaries on December 2, 2013.
	The following condensed consolidating financial statements present the financial information of (i) Dynegy (Parent), which is the parent and issuer of the Senior Notes, on a stand-alone, unconsolidated basis, (ii) Escrow Issuers, which are the finance company issuers of the Notes, (iii) the guarantor subsidiaries of Dynegy, (iv) the non-guarantor subsidiaries of Dynegy and (v) the eliminations necessary to arrive at the information for Dynegy on a consolidated basis.
	These statements should be read in conjunction with the unaudited consolidated financial statements and notes thereto of Dynegy. The supplemental condensed consolidating financial information has been prepared pursuant to the rules and regulations for condensed financial information and does not include all disclosures included in annual financial statements.
	For purposes of the condensed consolidating financial information, a portion of our intercompany receivable which we do not consider to be likely of settlement has been classified as equity as of March 31, 2015 and December 31, 2014.
	Condensed Consolidating Balance Sheet as of March 31, 2015
	(amounts in millions)
		Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	Current Assets
	Cash and cash equivalents	$	1,438		$	—		$	122		$	174		$	—		$	1,734
	Restricted cash	—			205			—			—			—			205
	Accounts receivable, net	15			—			615			163			(525		)	268
	Inventory	—			—			90			134			—			224
	Other current assets	17			7			127			75			—			226
	Total Current Assets	1,470			212			954			546			(525		)	2,657
	Property, Plant and Equipment, Net	—			—			2,781			446			—			3,227
	Other Assets
	Investment in affiliates	5,986			—			—			—			(5,986		)	—
	Other long-term assets	57			54			67			53			—			231
	Restricted cash	—			5,100			—			—			—			5,100
	Intercompany note receivable	11			—			—			—			(11		)	—
	Total Assets	$	7,524		$	5,366		$	3,802		$	1,045		$	(6,522	)	$	11,215
	Current Liabilities
	Accounts payable	$	114		$	260		$	159		$	240		$	(525	)	$	248
	Other current liabilities	71			166			155			180			—			572
	Total Current Liabilities	185			426			314			420			(525		)	820
	Long-term debt	1,275			5,100			—			702			—			7,077
	Intercompany note payable	3,042			—			—			11			(3,053		)	—
	Other long-term liabilities	186			—			109			188			—			483
	Total Liabilities	4,688			5,526			423			1,321			(3,578		)	8,380
	Stockholders’ Equity
	Dynegy Stockholders’ Equity	2,836			(160		)	6,421			(275		)	(5,986		)	2,836
	Intercompany note receivable	—			—			(3,042		)	—			3,042			—
	Total Dynegy Stockholders’ Equity	2,836			(160		)	3,379			(275		)	(2,944		)	2,836
	Noncontrolling interest	—			—			—			(1		)	—			(1		)
	Total Equity	2,836			(160		)	3,379			(276		)	(2,944		)	2,835
	Total Liabilities and Equity	$	7,524		$	5,366		$	3,802		$	1,045		$	(6,522	)	$	11,215
	Condensed Consolidating Balance Sheet as of December 31, 2014
	(amounts in millions)
		Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	Current Assets
	Cash and cash equivalents	$	1,642		$	—		$	54		$	174		$	—		$	1,870
	Restricted cash	—			113			—			—			—			113
	Accounts receivable, net	14			—			672			176			(592		)	270
	Inventory	—			—			88			120			—			208
	Other current assets	9			6			125			73			—			213
	Total Current Assets	1,665			119			939			543			(592		)	2,674
	Property, Plant and Equipment, Net	—			—			2,812			443			—			3,255
	Other Assets
	Investment in affiliates	6,133			—			—			—			(6,133		)	—
	Other long-term assets	46			47			53			57			—			203
	Restricted cash	—			5,100			—			—			—			5,100
	Intercompany note receivable	17			—			—			—			(17		)	—
	Total Assets	$	7,861		$	5,266		$	3,804		$	1,043		$	(6,742	)	$	11,232
	Current Liabilities
	Accounts payable	$	310		$	166		$	112		$	220		$	(592	)	$	216
	Other current liabilities	51			67			250			97			—			465
	Total Current Liabilities	361			233			362			317			(592		)	681
	Long-term debt	1,277			5,100			—			698			—			7,075
Intercompany note payable	3,042			—			—			17			(3,059		)	—
Other long-term liabilities	158			—			105			190			—			453
Total Liabilities	4,838			5,333			467			1,222			(3,651		)	8,209
Stockholders’ Equity
Dynegy Stockholders’ Equity	3,023			(67		)	6,379			(179		)	(6,133		)	3,023
Intercompany note receivable	—			—			(3,042		)	—			3,042			—
Total Dynegy Stockholders’ Equity	3,023			(67		)	3,337			(179		)	(3,091		)	3,023
Noncontrolling interest	—			—			—			—			—			—
Total Equity	3,023			(67		)	3,337			(179		)	(3,091		)	3,023
Total Liabilities and Equity	$	7,861		$	5,266		$	3,804		$	1,043		$	(6,742	)	$	11,232
Condensed Consolidating Statements of Operations for the Three Months Ended March 31, 2015
(amounts in millions)
	Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
Revenues	$	—		$	—		$	413		$	219		$	—		$	632
Cost of sales, excluding depreciation expense	—			—			(239		)	(138		)	—			(377		)
Gross margin	—			—			174			81			—			255
Operating and maintenance expense	—			—			(60		)	(51		)	—			(111		)
Depreciation expense	—			—			(56		)	(8		)	—			(64		)
General and administrative expense	(1		)	—			(17		)	(12		)	—			(30		)
Acquisition and integration costs	—			—			—			(90		)	—			(90		)
Operating income (loss)	(1		)	—			41			(80		)	—			(40		)
Equity in losses from investments in affiliates	(147		)	—			—			—			147			—
Interest expense	(27		)	(93		)	—			(16		)	—			(136		)
Other income and expense, net	(5		)	—			—			—			—			(5		)
Income (loss) before income taxes	(180		)	(93		)	41			(96		)	147			(181		)
Income tax expense	—			—			—			—			—			—
Net income (loss)	(180		)	(93		)	41			(96		)	147			(181		)
Less: Net loss attributable to noncontrolling interest	—			—			—			(1		)	—			(1		)
Net income (loss) attributable to Dynegy Inc.	$	(180	)	$	(93	)	$	41		$	(95	)	$	147		$	(180	)
Condensed Consolidating Statements of Operations for the Three Months Ended March 31, 2014
(amounts in millions)
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
Revenues	$	—		$	558		$	204		$	—		$	762
Cost of sales, excluding depreciation expense	—			(393		)	(159		)	—			(552		)
Gross margin	—			165			45			—			210
Operating and maintenance expense	—			(63		)	(47		)	—			(110		)
Depreciation expense	—			(59		)	(8		)	—			(67		)
General and administrative expense	(2		)	(14		)	(10		)	—			(26		)
Acquisition and integration costs	—			—			(6		)	—			(6		)
Operating income (loss)	(2		)	29			(26		)	—			1
Equity in losses from investments in affiliates	(39		)	—			—			39			—
Interest expense	(16		)	—			(14		)	—			(30		)
Other income and expense, net	(6		)	—			—			—			(6		)
Income (loss) before income taxes	(63		)	29			(40		)	39			(35		)
Income tax benefit (expense)	22			—			(24		)	—			(2		)
Net income (loss)	(41		)	29			(64		)	39			(37		)
Less: Net income attributable to noncontrolling interest	—			—			4			—			4
Net income (loss) attributable to Dynegy Inc.	$	(41	)	$	29		$	(68	)	$	39		$	(41	)
Condensed Consolidating Statements of Comprehensive Income (Loss) for the Three Months Ended March 31, 2015
(amounts in millions)
	Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
Net income (loss)	$	(180	)	$	(93	)	$	41		$	(96	)	$	147		$	(181	)
Amounts reclassified from accumulated other comprehensive income:
Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	(1		)	—			—			—			—			(1		)
Other comprehensive loss, net of tax	(1		)	—			—			—			—			(1		)
Comprehensive income (loss)	(181		)	(93		)	41			(96		)	147			(182		)
Less: Comprehensive loss attributable to noncontrolling interest	—			—			—			(1		)	—			(1		)
Total comprehensive income (loss) attributable to Dynegy Inc.	$	(181	)	$	(93	)	$	41		$	(95	)	$	147		$	(181	)
Condensed Consolidating Statements of Comprehensive Income (Loss) for the Three Months Ended March 31, 2014
(amounts in millions)
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
Net income (loss)	$	(41	)	$	29		$	(64	)	$	39		$	(37	)
Other comprehensive income (loss) before reclassifications:
Actuarial loss, net of tax of zero	—			—			(3		)	—			(3		)
Amounts reclassified from accumulated other comprehensive income:
Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	(1		)	—			—			—			(1		)
Other comprehensive income (loss) from investment in affiliates	(3		)	—			—			3			—
Other comprehensive income (loss), net of tax	(4		)	—			(3		)	3			(4		)
Comprehensive income (loss)	(45		)	29			(67		)	42			(41		)
Less: Comprehensive income (loss) attributable to noncontrolling interest	(1		)	—			3			1			3
Total comprehensive income (loss) attributable to Dynegy Inc.	$	(44	)	$	29		$	(70	)	$	41		$	(44	)
Condensed Consolidating Statements of Cash Flow for the Three Months Ended March 31, 2015
(amounts in millions)
	Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	$	2		$	(94	)	$	46		$	(9	)	$	—		$	(55	)
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	—			—			(29		)	(11		)	—			(40		)
Net intercompany transfers	(188		)	—			—			—			188			—
Net cash provided by (used in) investing activities	(188		)	—			(29		)	(11		)	188			(40		)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of borrowings	(2		)	—			(23		)	—			—			(25		)
Dividends paid	(7		)	—			—			—			—			(7		)
Net intercompany transfers	—			94			74			20			(188		)	—
Interest rate swap settlement payments	(4		)	—			—			—			—			(4		)
Other financing	(5		)	—			—			—			—			(5		)
Net cash provided by (used in) financing activities	(18		)	94			51			20			(188		)	(41		)
Net increase (decrease) in cash and cash equivalents	(204		)	—			68			—			—			(136		)
Cash and cash equivalents, beginning of period	1,642			—			54			174			—			1,870
Cash and cash equivalents, end of period	$	1,438		$	—		$	122		$	174		$	—		$	1,734
Condensed Consolidating Statements of Cash Flow for the Three Months Ended March 31, 2014
(amounts in millions)
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	$	(9	)	$	140		$	35		$	—		$	166
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	—			(6		)	(11		)	—			(17		)
Net intercompany transfers	113			—			—			(113		)	—
Net cash provided by (used in) investing activities	113			(6		)	(11		)	(113		)	(17		)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from long-term borrowings, net of financing costs	(1		)	12			—			—			11
Repayments of borrowings	(2		)	—			—			—			(2		)
Net intercompany transfers	—			(142		)	29			113			—
Interest rate swap settlement payments	(4		)	—			—			—			(4		)
Other financing	(1		)	—			—			—			(1		)
Net cash provided by (used in) financing activities	(8		)	(130		)	29			113			4
Net increase in cash and cash equivalents	96			4			53			—			153
Cash and cash equivalents, beginning of period	474			154			215			—			843
Cash and cash equivalents, end of period	$	570		$	158		$	268		$	—		$	996

Accounting_Policies

Accounting Policies	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Accounting Policies	Note 2—Accounting Policies
	The accounting policies followed by the Company are set forth in Note 2—Summary of Significant Accounting Policies in our Form 10-K. There have been no significant changes to these policies during the three months ended March 31, 2015.
	The preparation of consolidated financial statements in conformity with GAAP requires management to make informed estimates and judgments that affect our reported financial position and results of operations based on currently available information.  Actual results could differ materially from our estimates. The results of operations for the interim periods presented in this Form 10-Q are not necessarily indicative of the results to be expected for the full year or any other interim period due to seasonal fluctuations in demand for our energy products and services, changes in commodity prices, timing of maintenance and other expenditures and other factors.
	Accounting Standards Adopted During the Current Period
	Reporting Discontinued Operations and Asset Disposals. In April 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-08-Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosure of Disposals of Components of an Entity. The amendments in this ASU change the requirements for reporting discontinued operations in Subtopic 205-20. An entity is required to report within discontinued operations on the statement of operations the results of a component or group of components of an entity if the disposal represents a strategic shift that has, or will have, a major effect on an entity’s operations and financial results. Additionally, the associated assets and liabilities are required to be presented separately from other assets and liabilities on the balance sheet for all comparative periods. The ASU includes updated guidance regarding what meets the definition of a component of an entity. The new financial statement presentation provisions relating to this ASU are prospective and effective for interim and annual periods beginning after December 15, 2014, with early adoption permitted. The adoption of this ASU did not have a material impact on our financial statements or disclosures.
	Accounting Standards Not Yet Adopted
	Debt Issuance Costs. In April 2015, the FASB issued ASU 2015-03-Interest-Imputation of Interest (Subtopic 835-30).  The amendments in this ASU require that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts.  The recognition and measurement guidance for debt issuance costs are not affected by the amendments in this update.  The guidance in this ASU is effective for interim and annual periods beginning after December 15, 2015, with early adoption permitted.  The adoption of this ASU should be applied on a retrospective basis, affecting all balance sheet periods presented.  We do not anticipate the adoption of this ASU will have a material impact on the presentation of our consolidated balance sheets.
	Consolidation. In February 2015, the FASB issued ASU 2015-02-Consolidation (Topic 810). The amendments in this ASU respond to concerns about the current accounting for consolidation of certain legal entities, in particular: (i) consolidation of limited partnerships and similar legal entities, (ii) evaluating fees paid to a decision maker or a service provider as a variable interest, (iii) the effect of fee arrangements on the primary beneficiary determination, (iv) the effect of related parties on the primary beneficiary determination and (v) consolidation of certain investment funds. The guidance in this ASU is effective for interim and annual periods beginning after December 15, 2015, with early adoption permitted in an interim period. We do not anticipate the adoption of this ASU will have a material impact on our consolidated financial statements.
	Extraordinary and Unusual Items. In January 2015, the FASB issued ASU 2015-01-Income Statement-Extraordinary and Unusual Items (Subtopic 225-20). The amendments in this ASU eliminate from GAAP the concept of extraordinary items and will no longer require separate classification of them within the statement of operations. Presentation and disclosure guidance for items that are unusual in nature or occur infrequently will be retained and will be expanded to include items that are both unusual in nature and infrequently occurring. The guidance in this ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015.  Reporting entities may elect to apply the amendments prospectively only, or retrospectively for all prior periods presented in the financial statements.  Early adoption is permitted provided that the guidance is applied from the beginning of the fiscal year of adoption. We do not anticipate the adoption of this ASU will have a material impact on our consolidated financial statements.
	Revenue from Contracts with Customers. In May 2014, the FASB and International Accounting Standards Board (“IASB”) jointly issued ASU 2014-09-Revenue from Contracts with Customers (Topic 606). The amendments in this ASU develop a common revenue standard for GAAP and International Financial Reporting Standards (“IFRS”) by removing inconsistencies and weaknesses in revenue requirements, providing a more robust framework for addressing revenue issues, improving comparability of revenue recognition practices, providing more useful information to users of financial statements and simplifying the preparation of financial statements. The guidance in this ASU is effective for interim and annual periods beginning after December 15, 2017, with early adoption permitted for interim and annual periods beginning after December 15, 2016. We are currently assessing this ASU; however, we do not anticipate the adoption of this ASU will have a material impact on our consolidated financial statements.

Risk_Management_Activities_Der

Risk Management Activities, Derivatives and Financial Instruments	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Risk Management Activities, Derivatives and Financial Instruments	Note 3—Risk Management Activities, Derivatives and Financial Instruments
	The nature of our business necessarily involves commodity market and financial risks.  Specifically, we are exposed to commodity price variability related to our power generation business.  Our commercial team manages these commodity price risks with financially settled and other types of contracts consistent with our commodity risk management policy.  Our treasury team manages our interest rate risk.
	Our commodity risk management policy gives us the flexibility to sell energy and capacity and purchase fuel through a combination of spot market sales and near-term contractual arrangements (generally over a rolling one- to three-year time frame).  Our commodity risk management goal is to protect cash flow in the near-term while keeping the ability to capture value longer-term.
	Many of our contractual arrangements are derivative instruments and are accounted for at fair value as part of Revenues in our unaudited consolidated statements of operations.  We have other contractual arrangements such as capacity forward sales arrangements, tolling arrangements, fixed price coal purchases and retail power sales which do not receive recurring fair value accounting treatment because these arrangements do not meet the definition of a derivative or are designated as “normal purchase, normal sale,” in accordance with Accounting Standards Codification (“ASC”) 815.  As a result, the gains and losses with respect to these arrangements are not reflected in the unaudited consolidated statements of operations until the delivery occurs.
	Quantitative Disclosures Related to Financial Instruments and Derivatives
	As of March 31, 2015, we had net purchases and sales of derivative contracts outstanding in the following quantities:
	Contract Type		Quantity			Unit of Measure		Fair Value (1)
	(dollars and quantities in millions)		Purchases (Sales)					Asset (Liability)
	Commodity contracts:
	Electricity derivatives (2)		(18	)		MWh		$	80
	Electricity basis derivatives (3)		(12	)		MWh		$	(6	)
	Natural gas derivatives (2)		85			MMBtu		$	(81	)
	Natural gas basis derivatives		22			MMBtu		$	(2	)
	Diesel fuel derivatives		6			Gallon		$	(5	)
	Coal derivatives		—			Metric Ton		$	(1	)
	Crude oil derivatives		—			Barrel		$	(2	)
	Emissions derivatives		5			Metric Ton		$	1
	Interest rate swaps		783			U.S. Dollar		$	(49	)
	Common stock warrants (4)		16			Warrant		$	(66	)
	__________________________________________
	-1	Includes both asset and liability risk management positions, but excludes margin and collateral netting of $2 million.
	-2	Mainly comprised of swaps, options and physical forwards.
	-3	Comprised of FTRs and swaps.
	-4	Each warrant is convertible into one share of Dynegy common stock.
	Derivatives on the Balance Sheet.  The following tables present the fair value and balance sheet classification of derivatives in the unaudited consolidated balance sheets as of March 31, 2015 and December 31, 2014. As of March 31, 2015 and December 31, 2014, there were no gross amounts available to be offset that were not offset in our unaudited consolidated balance sheets.
						March 31, 2015
										Gross amounts offset in the balance sheet
	Contract Type			Balance Sheet Location		Gross Fair Value				Contract Netting			Collateral or Margin Received or Paid		Net Fair Value
	(amounts in millions)
	Derivative assets:
		Commodity contracts		Assets from risk management activities		$	118			$	(34	)	$		$	84
		Total derivative assets				$	118			$	(34	)	$	—	$	84
	Derivative liabilities:
		Commodity contracts		Liabilities from risk management activities		$	(134	)		$	34		$	2	$	(98	)
		Interest rate contracts		Liabilities from risk management activities		(49		)		—			—		(49		)
		Common stock warrants		Other long-term liabilities		(66		)		—			—		(66		)
		Total derivative liabilities				$	(249	)		$	34		$	2	$	(213	)
	Total derivatives					$	(131	)		$	—		$	2	$	(129	)
						31-Dec-14
										Gross amounts offset in the balance sheet
	Contract Type			Balance Sheet Location		Gross Fair Value				Contract Netting			Collateral or Margin Received or Paid		Net Fair Value
	(amounts in millions)
	Derivative assets:
		Commodity contracts		Assets from risk management activities		$	115			$	(35	)	$	—	$	80
		Total derivative assets				$	115			$	(35	)	$	—	$	80
	Derivative liabilities:
		Commodity contracts		Liabilities from risk management activities		$	(163	)		$	35		$	9	$	(119	)
		Interest rate contracts		Liabilities from risk management activities		(44		)		—			—		(44		)
		Common stock warrants		Other long-term liabilities		(61		)		—			—		(61		)
		Total derivative liabilities				$	(268	)		$	35		$	9	$	(224	)
	Total derivatives					$	(153	)		$	—		$	9	$	(144	)
	Certain of our derivative instruments have credit limits that require us to post collateral. The amount of collateral required to be posted is a function of the net liability position of the derivative as well as our established credit limit with the respective counterparty. If our credit rating were to change, the counterparties could require us to post additional collateral. The amount of additional collateral that would be required to be posted would vary depending on the extent of change in our credit rating as well as the requirements of the individual counterparty. The aggregate fair value of all commodity derivative instruments with credit-risk-related contingent features that are in a liability position that are not fully collateralized (excluding transactions with our clearing brokers that are fully collateralized) at March 31, 2015 is $1 million for which we have posted no collateral. Our remaining derivative instruments do not have credit-related collateral contingencies as they are included within our first-lien collateral program.
	The following table summarizes our total cash collateral posted as of March 31, 2015 and December 31, 2014, along with the location on the balance sheet and the amount applied against our short-term risk management liabilities.
	Location on balance sheet		31-Mar-15				31-Dec-14
	(amounts in millions)
	Gross collateral posted with counterparties		$	59			$	49
	Less: Collateral netted against risk management liabilities		2				9
	Net collateral within Prepayments and other current assets		$	57			$	40
	Impact of Derivatives on the Consolidated Statements of Operations
	The following discussion and tables present the location and amount of gains and losses on derivative instruments in our unaudited consolidated statements of operations.
	Financial Instruments Not Designated as Hedges.  We elect not to designate derivatives related to our power generation business and interest rate instruments as cash flow or fair value hedges.  Thus, we account for changes in the fair value of these derivatives within our unaudited consolidated statements of operations.
	The recognized impact of derivative financial instruments on our unaudited consolidated statements of operations for the three months ended March 31, 2015 and 2014 is presented below.
	Derivatives Not Designated as Hedges		Location of Gain (Loss)		Three Months Ended March 31,
			Recognized in Income on
		Derivatives		2015				2014
(amounts in millions)
Commodity contracts		Revenues		$	19			$	(173	)
Interest rate contracts		Interest expense		$	(9	)		$	3
Common stock warrants		Other income (expense), net		$	(5	)		$	(6	)

Fair_Value_Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 4—Fair Value Measurements
	We apply the market approach for recurring fair value measurements, employing valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs.  We have consistently used the same valuation techniques for all periods presented.  Please read Note 2—Summary of Significant Accounting Policies—Fair Value Measurements in our Form 10-K for further discussion.
	The following tables set forth, by level within the fair value hierarchy, our financial assets and liabilities that were accounted for at fair value on a recurring basis as of March 31, 2015 and December 31, 2014 and are presented on a gross basis before consideration of amounts netted under master netting agreements and the application of collateral and margin paid.
			Fair Value as of March 31, 2015
	(amounts in millions)		Level 1				Level 2				Level 3				Total
	Assets:
	Assets from commodity risk management activities:
	Electricity derivatives		$	—			$	96			$	17			$	113
	Natural gas derivatives		—				4				—				4
	Emissions derivatives		—				1				—				1
	Total assets from commodity risk management activities		$	—			$	101			$	17			$	118
	Liabilities:														.
	Liabilities from commodity risk management activities:
	Electricity derivatives		$	—			$	(26	)		$	(13	)		$	(39	)
	Natural gas derivatives		—				(87		)		—				(87		)
	Diesel fuel derivatives		—				(5		)		—				(5		)
	Crude oil derivatives		—				(2		)		—				(2		)
	Coal derivatives		—				(1		)		—				(1		)
	Total liabilities from commodity risk management activities		—				(121		)		(13		)		(134		)
	Liabilities from interest rate contracts		—				(49		)		—				(49		)
	Liabilities from outstanding common stock warrants		(66		)		—				—				(66		)
	Total liabilities		$	(66	)		$	(170	)		$	(13	)		$	(249	)
			Fair Value as of December 31, 2014
	(amounts in millions)		Level 1				Level 2				Level 3				Total
	Assets:
	Assets from commodity risk management activities:
	Electricity derivatives		$	—			$	88			$	22			$	110
	Natural gas derivatives		—				3				—				3
	Emissions derivatives		—				2				—				2
	Total assets from commodity risk management activities		$	—			$	93			$	22			$	115
	Liabilities:
	Liabilities from commodity risk management activities:
	Electricity derivatives		$	—			$	(27	)		$	(26	)		$	(53	)
	Natural gas derivatives		—				(100		)		—				(100		)
	Diesel derivatives		—				(6		)		—				(6		)
	Crude oil derivatives		—				(3		)		—				(3		)
	Coal derivatives		—				(1		)		—				(1		)
	Total liabilities from commodity risk management activities		—				(137		)		(26		)		(163		)
	Liabilities from interest rate contracts		—				(44		)		—				(44		)
	Liabilities from outstanding common stock warrants		(61		)		—				—				(61		)
	Total liabilities		$	(61	)		$	(181	)		$	(26	)		$	(268	)
	Level 3 Valuation Methods. The electricity derivatives classified within Level 3 include physical sales and financial swaps executed in illiquid trading locations and FTRs.  The curves used to generate the fair value of the physical sales and financial swaps are based on basis adjustments applied to forward curves for liquid trading points, while the forward market price of FTRs is derived using historical congestion patterns within the marketplace.
	Sensitivity to Changes in Significant Unobservable Inputs for Level 3 Valuations. The significant unobservable inputs used in the fair value measure of our commodity instruments categorized within Level 3 of the fair value hierarchy are estimates of forward congestion power price spreads and illiquid power location pricing basis to liquid locations. These estimates are generally independent of each other. Power price spreads are generally based on observable markets where available, or derived from historical prices and forward market prices from similar observable markets when not available. Increases in the price of the spread on a buy or sell position in isolation would result in a higher/lower fair value measurement. The significant unobservable inputs used in the valuation of Dynegy’s contracts classified as Level 3 as of March 31, 2015 are as follows:
	Transaction Type		Quantity			Unit of Measure		Net Fair Value				Valuation Technique		Significant Unobservable Input		Significant Unobservable Inputs Range
	(dollars in millions)
	Electricity derivatives:
	Forward contracts—power (1)		(4	)		Million MWh		$	5			Basis spread + liquid location		Basis spread		$5.00-$7.00
	FTRs		7			Million MWh		$	(1	)		Historical congestion		Forward price		$0.00-$3.00
	__________________________________________
	-1	Represents forward financial and physical transactions at illiquid pricing locations.
	The following tables set forth a reconciliation of changes in the fair value of financial instruments classified as Level 3 in the fair value hierarchy:
			Three Months Ended March 31, 2015
	(amounts in millions)		Electricity				Total
			Derivatives
	Balance at December 31, 2014		$	(4	)		$	(4	)
	Total gains included in earnings		3				3
	Settlements (1)		5				5
	Balance at March 31, 2015		$	4			$	4
	Unrealized gains relating to instruments held as of March 31, 2015		$	3			$	3
			Three Months Ended March 31, 2014
	(amounts in millions)		Electricity				Heat Rate Derivatives				Total
			Derivatives
	Balance at December 31, 2013		$	11			$	(1	)		$	10
	Total losses included in earnings		(23		)		—				(23		)
Settlements (1)		2				—				2
Balance at March 31, 2014		$	(10	)		$	(1	)		$	(11	)
Unrealized losses relating to instruments held as of March 31, 2014		$	(23	)		$	—			$	(23	)
__________________________________________
-1	For purposes of these tables, we define settlements as the beginning of period fair value of contracts that settled during the period.
Gains and losses recognized for Level 3 recurring items are included in Revenues on our unaudited consolidated statements of operations for commodity derivatives.  We believe an analysis of commodity instruments classified as Level 3 should be undertaken with the understanding that these items generally serve as economic hedges of our power generation portfolio.  We did not have any transfers between Level 1, Level 2 and Level 3 for the three months ended March 31, 2015 and 2014.
Nonfinancial Assets and Liabilities.  Nonfinancial assets and liabilities that are measured at fair value on a nonrecurring basis are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of fair value assets and liabilities and their placement within the fair value hierarchy levels.
We did not have any material nonfinancial assets or liabilities measured at fair value on a non-recurring basis during the three months ended March 31, 2015 and 2014.
Fair Value of Financial Instruments.  The following table discloses the fair value of financial instruments recognized on our unaudited consolidated balance sheets.  Unless otherwise noted, the fair value of debt as reflected in the table has been calculated based on the average of certain available broker quotes as of March 31, 2015 and December 31, 2014, respectively.
		March 31, 2015								December 31, 2014
(amounts in millions)		Carrying				Fair				Carrying				Fair
		Amount				Value				Amount				Value
Dynegy Inc.:
Tranche B-2 Term Loan, due 2020 (1)(2)		$	(783	)		$	(786	)		$	(785	)		$	(775	)
5.875% Senior Notes, due 2023 (2)		$	(500	)		$	(486	)		$	(500	)		$	(475	)
Emissions Repurchase Agreements (2)		$	—			$	—			$	(23	)		$	(23	)
Interest rate derivatives (2)		$	(49	)		$	(49	)		$	(44	)		$	(44	)
Commodity-based derivative contracts (3)		$	(16	)		$	(16	)		$	(48	)		$	(48	)
Common stock warrants (4)		$	(66	)		$	(66	)		$	(61	)		$	(61	)
Dynegy Finance I, Inc.:
6.75% Senior Notes, due 2019 (2)		$	(840	)		$	(874	)		$	(840	)		$	(853	)
7.375% Senior Notes, due 2022 (2)		$	(700	)		$	(739	)		$	(700	)		$	(711	)
7.625% Senior Notes, due 2024 (2)		$	(500	)		$	(531	)		$	(500	)		$	(509	)
Dynegy Finance II, Inc.:
6.75% Senior Notes, due 2019 (2)		$	(1,260	)		$	(1,310	)		$	(1,260	)		$	(1,279	)
7.375% Senior Notes, due 2022 (2)		$	(1,050	)		$	(1,108	)		$	(1,050	)		$	(1,066	)
7.625% Senior Notes, due 2024 (2)		$	(750	)		$	(797	)		$	(750	)		$	(763	)
Genco:
7.95% Senior Notes Series F, due 2032 (2)(5)		$	(224	)		$	(240	)		$	(224	)		$	(241	)
7.00% Senior Notes Series H, due 2018 (2)(5)		$	(270	)		$	(278	)		$	(268	)		$	(264	)
6.30% Senior Notes Series I, due 2020 (2)(5)		$	(208	)		$	(217	)		$	(206	)		$	(208	)
__________________________________________
-1	Carrying amount includes an unamortized discount of $3 million as of March 31, 2015 and December 31, 2014. Please read Note 8—Debt for further discussion.
-2	The fair values of these financial instruments are classified as Level 2 within the fair value hierarchy levels.
-3	Carrying amount of commodity-based derivative contracts excludes $2 million and $9 million of cash posted as collateral, as of March 31, 2015 and December 31, 2014, respectively.
-4	The fair value of the common stock warrants is classified as Level 1 within the fair value hierarchy levels.
-5	Combined carrying amounts as of March 31, 2015 and December 31, 2014 include unamortized discounts of $123 million and $127 million, respectively. Please read Note 8—Debt for further discussion.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income	3 Months Ended
	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income	Note 5—Accumulated Other Comprehensive Income
	Changes in accumulated other comprehensive income, net of tax, by component are as follows:
			Three Months Ended March 31,
	(amounts in millions)		2015			2014
	Beginning of period		$	20		$	58
	Other comprehensive loss before reclassifications:
	Actuarial loss (net of tax of zero and zero, respectively)		—			(2		)
	Amounts reclassified from accumulated other comprehensive income:
	Amortization of unrecognized prior service cost (credit) and actuarial loss (gain) (net of tax of zero and zero, respectively) (1)		(1		)	(1		)
	Net current period other comprehensive loss, net of tax		(1		)	(3		)
	End of period		$	19		$	55
	__________________________________________
	-1	Amounts are associated with our defined benefit pension and other post-employment benefit plans and are included in the computation of net periodic pension cost (gain). Please read Note 11—Pension and Other Post-Employment Benefit Plans for further discussion.

Inventory

Inventory	3 Months Ended
	Mar. 31, 2015
Inventory Disclosure [Abstract]
Inventory	Note 6—Inventory
	A summary of our inventories is as follows:
	(amounts in millions)	March 31, 2015		December 31, 2014
	Materials and supplies	$	84	$	83
	Coal	134		119
	Fuel oil	3		3
	Emissions allowances	2		2
	Other	1		1
	Total	$	224	$	208

Intangible_Assets_and_Liabilit

Intangible Assets and Liabilities	3 Months Ended
	Mar. 31, 2015
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Intangible Assets and Liabilities	Note 7—Intangible Assets and Liabilities
	The following table summarizes the components of our intangible assets and liabilities as of March 31, 2015 and December 31, 2014:
			March 31, 2015									December 31, 2014
	(amounts in millions)		Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount			Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount
	Intangible Assets:
	Electricity contracts		$	111		$	(53	)	$	58		$	111		$	(46	)	$	65
	Total intangible assets		$	111		$	(53	)	$	58		$	111		$	(46	)	$	65
	Intangible Liabilities:
	Electricity contracts		$	(20	)	$	14		$	(6	)	$	(20	)	$	14		$	(6	)
	Coal contracts		(122		)	63			(59		)	(122		)	54			(68		)
	Gas transport contracts		(24		)	19			(5		)	(24		)	17			(7		)
	Total intangible liabilities		$	(166	)	$	96		$	(70	)	$	(166	)	$	85		$	(81	)
	Intangible assets and liabilities, net		$	(55	)	$	43		$	(12	)	$	(55	)	$	39		$	(16	)
	The following table presents our amortization expense (revenue) of intangible assets and liabilities for the three months ended March 31, 2015 and 2014:
			Three Months Ended March 31,
	(amounts in millions)		2015			2014
	Electricity contracts, net (1)		$	7		$	29
	Coal contracts, net (1)		(9		)	(11		)
	Gas transport contracts (2)		(2		)	(2		)
	Total		$	(4	)	$	16
	__________________________________________
	-1	The amortization of these contracts is recognized in Revenues or Cost of sales in our unaudited consolidated statements of operations.
	-2	The amortization of these contracts is recognized in Cost of sales in our unaudited consolidated statements of operations.

Debt

Debt	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Debt	Note 8—Debt
	A summary of our long-term debt is as follows:
	(amounts in millions)		March 31, 2015			December 31, 2014
	Dynegy Inc.:
	Tranche B-2 Term Loan, due 2020		$	786		$	788
	5.875% Senior Notes, due 2023		500			500
	Revolving Facility		—			—
	Emissions Repurchase Agreements		—			23
	Dynegy Finance I, Inc.:
	6.75% Senior Notes, due 2019		840			840
	7.375% Senior Notes, due 2022		700			700
	7.625% Senior Notes, due 2024		500			500
	Dynegy Finance II, Inc.:
	6.75% Senior Notes, due 2019		1,260			1,260
	7.375% Senior Notes, due 2022		1,050			1,050
	7.625% Senior Notes, due 2024		750			750
	Genco:
	7.95% Senior Notes Series F, due 2032		275			275
	7.00% Senior Notes Series H, due 2018		300			300
	6.30% Senior Notes Series I, due 2020		250			250
			7,211			7,236
	Unamortized discounts on debt, net		(126		)	(130		)
			7,085			7,106
	Less: Current maturities, including unamortized discounts, net		8			31
	Total Long-term debt		$	7,077		$	7,075
	Debt Issuance
	On October 27, 2014, we completed the issuance of $5.1 billion in aggregate principal amount of unsecured senior notes at a weighted average interest rate of 7.18 percent in tranches with maturities ranging from 2019 to 2024 (the “Notes”). The gross proceeds from the issuance of the Notes, less initial purchasers’ discounts and expenses, were placed into escrow pending the consummation of the Acquisitions. Please read Note 11—Debt in our Form 10-K and Note 15—Subsequent Events—Acquisition Financing for further discussion.
	Credit Agreement
	As of March 31, 2015, we had a $1.275 billion credit agreement that consisted of (i) an $800 million seven-year senior secured term loan B facility (the “Tranche B-2 Term Loan”) and (ii) a $475 million five-year senior secured revolving credit facility (the “Revolving Facility,” and collectively with the Tranche B-2 Term Loan, the “Credit Agreement”). Dynegy and its Subsidiary Guarantors (as defined in the Credit Agreement) also entered into an indenture pursuant to which Dynegy issued $500 million in aggregate principal amount of unsecured senior notes (the “Senior Notes”) at par. Following the closings of the Acquisitions in April 2015, the acquired entities were added as additional subsidiary guarantors. Please read Note 15—Subsequent Events—Acquisition Financing for further discussion.
	At March 31, 2015, there were no amounts drawn on the Revolving Facility; however, we had outstanding letters of credit of approximately $128 million, which reduces the amount available under the Revolving Facility.
	The Credit Agreement contains customary events of default and affirmative and negative covenants, subject to certain specified exceptions, including a Senior Secured Leverage Ratio (as defined in the Credit Agreement) calculated on a rolling four quarters basis. Based on the calculation outlined in the Credit Agreement, we are in compliance at March 31, 2015.
	In connection with the closings of the Acquisitions in April 2015, we entered into amendments to the Credit Agreement which provide for incremental revolving credit facilities that expand the credit available to us by an aggregate of $950 million ($600 million for the Duke Midwest Acquisition and $350 million for the EquiPower Acquisition). Please read Note 15—Subsequent Events—Acquisition Financing for further discussion.
	Genco Senior Notes
	On December 2, 2013, in connection with the acquisition of New Ameren Energy Resources, LLC (“AER”), Genco’s approximately $825 million in aggregate principal amount of unsecured senior notes (the “Genco Senior Notes”) remained outstanding as an obligation of Genco, a subsidiary of IPH.
	Genco’s indenture includes provisions that require Genco to maintain certain interest coverage and debt-to-capital ratios in order for Genco to pay dividends, to make principal or interest payments on subordinated borrowings, to make loans to or investments in affiliates, or to incur additional external, third-party indebtedness.
	The following table summarizes these required ratios:
			Required Ratio
	Restricted payment interest coverage ratio (1)		≥1.75
	Additional indebtedness interest coverage ratio (2)		≥2.50
	Additional indebtedness debt-to-capital ratio (2)		≤60%
	__________________________________________
	-1	As of the date of a restricted payment, as defined, the minimum ratio must have been achieved for the most recently ended four fiscal quarters and projected by management to be achieved for each of the subsequent four six-month periods.
	-2	Ratios must be computed on a pro forma basis considering the additional indebtedness to be incurred and the related interest expense. Other borrowings from third-party external sources are included in the definition of indebtedness and are subject to these incurrence tests.
	Genco’s debt incurrence-related ratio restrictions under the indenture may be disregarded if both Moody’s and S&P reaffirm the ratings in place at the time of the debt incurrence after considering the additional indebtedness.
	Based on March 31, 2015 calculations, Genco’s interest coverage ratios are less than the minimum ratios required for Genco to pay dividends and borrow additional funds from external, third-party sources.
	Letter of Credit Facilities
	On January 29, 2014, Illinois Power Marketing Company (“IPM”) entered into a fully cash collateralized Letter of Credit and Reimbursement Agreement with an issuing bank., as amended on May 16, 2014 (“LC Agreement”), pursuant to which the issuing bank agreed to issue from time to time, one or more standby letters of credit in an aggregate stated amount not to exceed $25 million at any one time to support performance obligations and other general corporate activities of IPM, provided that IPM deposits in an account controlled by the issuing bank an amount of cash sufficient to cover the face value of such requested letter of credit plus an additional percentage thereon. As of March 31, 2015, IPM had $10.5 million deposited with the issuing bank and $10 million in letters of credit outstanding.
	On September 18, 2014, Dynegy entered into a Letter of Credit Reimbursement Agreement with an issuing bank, and its affiliate (the “Lender”), for a letter of credit in an amount not to exceed $55 million. The facility has a one-year tenor and may be extended at the Lender’s option up to one additional year. At March 31, 2015, there was $55 million outstanding under this letter of credit.
	IPM Revolving Credit Facility
	On March 27, 2015, IPM entered into a revolving credit facility with the Lender for up to $25 million. The facility, which is collateralized by receivables, has a two-year tenor and may be extended if agreed to by both parties for one additional year.  Interest on the facility is LIBOR plus 500 basis points on issued letters of credit. At March 31, 2015, there were no amounts outstanding under this revolving facility.
	Emissions Repurchase Agreements
	In 2013, we entered into two repurchase transactions with a third party in which we sold $6 million in California Carbon Allowance (“CCA”) credits and $11 million of Regional Greenhouse Gas Initiative (“RGGI”) inventory and received cash. In the first quarter 2014, we entered into an additional repurchase agreement with a third party in which we sold $12 million of RGGI inventory and received cash. In October 2014, we repurchased all $6 million of the previously sold CCA credits and in February 2015, we repurchased all $23 million of the previously sold RGGI inventory.
	Interest Rate Swaps
	Subsequent to executing the Credit Agreement and issuing the Senior Notes, we amended our interest rate swaps to more closely match the terms of our Tranche B-2 Term Loan. The swaps have an aggregate notional value of approximately $783 million at an average fixed rate of 3.19 percent with a floor of one percent and expire during the second quarter 2020. In lieu of paying the breakage fees related to terminating the old swaps and issuing the new swaps, the costs were incorporated into the terms of the new swaps. As a result, any cash flows related to the settlement of the new swaps are reflected as a financing activity in our consolidated statement of cash flows.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 9—Commitments and Contingencies
	Legal Proceedings
	Set forth below is a summary of our material ongoing legal proceedings. We record accruals for estimated losses from contingencies when available information indicates that a loss is probable and the amount of the loss, or range of loss, can be reasonably estimated.  In addition, we disclose matters for which management believes a material loss is reasonably possible.  In all instances, management has assessed the matters below based on current information and made judgments concerning their potential outcome, giving consideration to the nature of the claim, the amount, if any, and nature of damages sought and the probability of success.  Management regularly reviews all new information with respect to such contingency and adjusts its assessment and estimates of such contingencies accordingly.  Because litigation is subject to inherent uncertainties including unfavorable rulings or developments, it is possible that the ultimate resolution of our legal proceedings could involve amounts that are different from our currently recorded accruals and that such differences could be material.
	In addition to the matters discussed below, we are party to other routine proceedings arising in the ordinary course of business or related to discontinued business operations.  Any accruals or estimated losses related to these matters are not material. In management’s judgment, the ultimate resolution of these matters will not have a material effect on our financial condition, results of operations or cash flows.
	Stockholder Litigation Relating to the 2011 Prepetition Restructuring. In connection with the prepetition restructuring and corporate reorganization of the Dynegy Holdings, LLC Debtor Entities and their non-debtor affiliates in 2011 (the “2011 Prepetition Restructuring”), and specifically the transfer of Dynegy Midwest Generation, LLC (“DMG”), a putative class action stockholder lawsuit captioned Charles Silsby v. Carl C. Icahn, et al., Case No. 12CIV2307 (the “Securities Litigation”), was filed in the U.S. District Court for the Southern District of New York. The lawsuit challenged certain disclosures made in connection with the transfer of DMG. As a result of the filing of the voluntary petition for bankruptcy by Dynegy Inc., this lawsuit was stayed as against Dynegy Inc. and, as a result of the confirmation of the Joint Chapter 11 Plan (the “Plan”), the claims against Dynegy Inc. in the Securities Litigation are permanently enjoined.
	On August 24, 2012, the lead plaintiff in the Securities Litigation filed an objection to the confirmation of the Plan asserting, among other things, that lead plaintiff should be permitted to opt-out of the non-debtor releases and injunctions (the “Non-Debtor Releases”) in the Plan on behalf of all putative class members. We opposed that relief. On October 1, 2012, the Bankruptcy Court ruled that lead plaintiff did not have standing to object to the Plan and did not have authority to opt-out of the Non-Debtor Releases on behalf of any other party-in-interest. Accordingly, the Securities Litigation may only proceed against the non-debtor defendants with respect to members of the putative class who individually opted out of the Non-Debtor Releases. The lead plaintiff filed a notice of appeal on October 10, 2012. On June 4, 2013, the District Court dismissed the appeal. On October 31, 2014, the Second Circuit affirmed the District Court’s dismissal based upon the lead plaintiff’s lack of standing. The lead plaintiff did not appeal to the U.S. Supreme Court.
	Additionally, on July 19, 2013, the defendants filed a substantive motion to dismiss the plaintiff’s remaining claims by any opt-out plaintiffs against the non-debtor defendants. On April 30, 2014, the District Court granted the defendants’ motion and dismissed the action.  Plaintiff is appealing this decision to the Second Circuit, but no decision has been issued.
	Gas Index Pricing Litigation.  We, several of our affiliates, our former joint venture affiliate and other energy companies were named as defendants in numerous lawsuits in state and federal court claiming damages resulting from alleged price manipulation and false reporting of natural gas prices to various index publications in the 2000-2002 time frame. Many of the cases have been resolved. All of the remaining cases contain similar claims that we individually, and in conjunction with other energy companies, engaged in an illegal scheme to inflate natural gas prices in four states by providing false information to natural gas index publications. In July 2011, the court granted defendants’ motions for summary judgment, thereby dismissing all of plaintiffs’ claims. Plaintiffs appealed the decision to the U.S. Court of Appeals for the Ninth Circuit which reversed the summary judgment on April 10, 2013. On August 26, 2013, we and the other defendants filed a request for review with the U.S. Supreme Court. On April 21, 2015, the Supreme Court issued its opinion affirming the Ninth Circuit’s decision and remanding the matter to the Nevada District Court for further proceedings.
	Illinova Generating Company Arbitration. In May 2007, our subsidiary Illinova Generating Company (“IGC”) received an adverse award in an arbitration brought by Ponderosa Pine Energy, LLC (“PPE”). The award required IGC to pay PPE $17 million, which IGC paid in June 2007 under protest while simultaneously seeking to vacate the award in the District Court of Dallas County, Texas. In March 2010, the Dallas District Court vacated the award, finding that one of the arbitrators had exhibited evident partiality. PPE appealed that decision to the Fifth District Court of Appeals in Dallas, Texas. Coincident with the appeal, IGC filed a claim against PPE seeking recovery of the $17 million plus interest. In September 2010, the Dallas District Court ordered PPE to deposit the $17 million principal in an interest-bearing escrow account jointly owned by IGC and PPE. On August 20, 2012, the Dallas Court of Appeals reversed the Dallas District Court and reinstated the award. IGC and the other respondents filed a petition for review with the Texas Supreme Court on December 5, 2012. On May 23, 2014, the Texas Supreme Court reversed the Dallas Court of Appeals and reinstated the trial court’s judgment vacating the arbitration award. The Texas Supreme Court denied rehearing on August 22, 2014. On November 20, 2014, PPE initiated a new arbitration against IGC and its co-respondents, but the Dallas District Court enjoined the arbitration from proceeding against IGC while any dispute over the escrow account remains pending. On December 16, 2014, the Dallas District Court entered a judgment requiring a full distribution of the escrow account to IGC and an additional $2.5 million in interest. PPE paid the $17 million principal to IGC from the escrow account, but filed a notice of appeal regarding the $17 million and $2.5 million interest judgment in March 2015.
	Other Contingencies
	Dam Safety Assessment Reports. In response to the failure at the TVA’s Kingston plant, the EPA initiated a nationwide investigation of the structural integrity of coal combustion residual (“CCR”) surface impoundments. The EPA assessments found all of our surface impoundments to be in satisfactory or fair condition, with the exception of the surface impoundments at the Baldwin and Hennepin facilities.
	The Baldwin and Hennepin reports rate the impoundments at each facility as “poor,” meaning that a deficiency was recognized for a required loading condition in accordance with applicable dam safety criteria or that certain documentation was lacking or incomplete or further critical studies are needed to identify any potential dam safety deficiencies.  The reports included recommendations for further studies, repairs and changes in operating practices.
	In response to the Hennepin report, we notified the EPA in July 2013 of our intent to close the Hennepin west CCR surface impoundment and make certain capital improvements to the east CCR surface impoundment. The preliminary estimated cost for closure of the west CCR surface impoundment, including post-closure monitoring, is approximately $5 million. As a result of these changes, we increased our asset retirement obligation (“ARO”) by approximately $2 million during the second quarter 2013. We performed further studies needed to support closure of the west CCR surface impoundment and submitted them to the Illinois EPA in August 2014. The capital improvements to the Hennepin east CCR surface impoundment berms were completed in 2014 at a cost of approximately $3 million.
	In response to the Baldwin report, we notified the EPA in April 2013 of our action plan, which included implementation of recommended operating practices and certain recommended studies. In 2014, we updated the EPA on the status of our Baldwin action plan, including the completion of certain studies and implementation of remedial measures and our ongoing evaluation of potential long-term measures in the context of our concurrent ongoing evaluation at Baldwin of groundwater corrective actions. In the first quarter 2015, we submitted to the EPA engineering design information concerning repairs of the affected south berm at the Baldwin CCR surface impoundment and a deformation analysis of the Baldwin CCR surface impoundment’s north berm. The nature and scope of repairs that ultimately may be needed at the Baldwin CCR surface impoundment to address the EPA’s dam safety assessment is dependent, in part, on the Illinois EPA’s response to our groundwater corrective action evaluation recommendations. Please read “Vermilion and Baldwin Groundwater” below for further discussion. At this time, if the Illinois EPA approves our proposed approach to address groundwater at Baldwin and the EPA concurs, we estimate the cost to repair the affected berm at the Baldwin CCR surface impoundment would be approximately $3 million. If such approach is not approved by the Illinois EPA we are unable, at this time, to estimate a reasonably possible cost, or range of costs, of repairs at the Baldwin CCR surface impoundment.
	New Source Review and Clean Air Litigation. Since 1999, the EPA has been engaged in a nationwide enforcement initiative to determine whether coal-fired power plants failed to comply with the requirements of the New Source Review and New Source Performance Standard provisions under the Clean Air Act (“CAA”) when the plants implemented modifications. The EPA’s initiative focuses on whether projects performed at power plants triggered various permitting requirements, including the need to install pollution control equipment.
	IPH Segment CAA Section 114 Information Requests. Commencing in 2005, the IPH facilities received a series of information requests from the EPA pursuant to Section 114(a) of the CAA. The requests sought detailed operating and maintenance history data with respect to the Coffeen, Newton, Edwards, Duck Creek and Joppa facilities. In August 2012, the EPA issued a Notice of Violation alleging that projects performed in 1997, 2006 and 2007 at the Newton facility violated Prevention of Significant Deterioration, Title V permitting and other requirements. We believe our defenses to the allegations described in the Notice of Violation are meritorious. A decision by the U.S. Court of Appeals for the Seventh Circuit in 2013 held that similar claims older than five years were barred by the statute of limitations. If not overturned, this decision may provide an additional defense to the allegations in the Newton facility Notice of Violation.
	Wood River CAA Section 114 Information Request. In May 2014, we received an information request from the EPA concerning our Coal segment’s Wood River facility’s compliance with the Illinois SIP and associated permits. We responded to the EPA’s request and believe that there are no issues with Wood River’s compliance, but we are unable to predict the EPA’s response, if any.
	Ultimate resolution of these matters could have a material adverse impact on our future financial condition, results of operations and cash flows. A resolution could result in increased capital expenditures for the installation of pollution control equipment, increased operations and maintenance expenses, and penalties. At this time we are unable to make a reasonable estimate of the possible costs, or range of costs, that might be incurred to resolve these matters.
	Edwards CAA Litigation. In April 2013, environmental groups filed a CAA citizen suit in the U.S. District Court for the Central District of Illinois alleging violations of opacity and particulate matter limits at our IPH segment’s Edwards facility. The District Court has scheduled the trial date for May 2016. IPH disputes the allegations and will defend the case vigorously. At this time we are unable to make a reasonable estimate of the possible costs, or range of costs, that might be incurred to resolve this matter.
	Vermilion and Baldwin Groundwater. In response to requests by the Illinois EPA, we have implemented hydrogeologic investigations for the CCR surface impoundment at our Baldwin facility and for two CCR surface impoundments at our Vermilion facility.
	Groundwater monitoring results indicate that the CCR surface impoundment at Baldwin impacts onsite groundwater. Also, at the request of the Illinois EPA, in late 2011 we initiated an investigation at Baldwin to determine if the facility’s CCR surface impoundment impacts offsite groundwater. Results of the offsite groundwater quality investigation at Baldwin, as submitted to the Illinois EPA on April 24, 2012, indicate two localized areas where Class I groundwater standards were exceeded.  The cause of the exceedances is uncertain. If offsite groundwater impacts are ultimately attributed to the Baldwin CCR surface impoundment and remediation measures are necessary in the future, we may incur significant costs that could have a material adverse effect on our financial condition, results of operations and cash flows. At this time we cannot reasonably estimate the costs, or range of costs, of corrective action that ultimately may be required at Baldwin.
	In April 2012, we submitted to the Illinois EPA proposed corrective action plans for two of the CCR surface impoundments at the Vermilion facility (i.e., the old east CCR surface impoundment and the north CCR surface impoundment).  The proposed corrective action plans reflect the results of a hydrogeologic investigation, which indicate that the facility’s old east and north CCR surface impoundments impact groundwater quality onsite and that such groundwater migrates offsite to the north of the property and to the adjacent Middle Fork of the Vermilion River.  The proposed corrective action plans include groundwater monitoring and recommend closure of both CCR surface impoundments, including installation of a geosynthetic cover.  In addition, we submitted an application to the Illinois EPA to establish a groundwater management zone while impacts from the facility are mitigated.  In March 2014, we submitted a revised corrective action plan for the old east CCR surface impoundment at Vermilion. Our estimated cost of the recommended closure alternative for both the Vermilion old east and north CCR surface impoundments, including post-closure care, is approximately $10 million. The Vermilion facility also has a third CCR surface impoundment, the new east CCR surface impoundment that is lined and is not known to impact groundwater.  Although not part of the proposed corrective action plans, if we decide to close the new east CCR surface impoundment by removing its CCR contents concurrent with the recommended closure alternative for the old east and north CCR surface impoundments, the associated estimated closure cost would add an additional $2 million to the above estimate.
	In July 2012, the Illinois EPA issued violation notices alleging violations of groundwater standards onsite at the Baldwin and Vermilion facilities. In December 2012, the Illinois EPA provided written notice that it may pursue legal action with respect to each matter through referral to the Illinois Office of the Attorney General. In accordance with work plans approved by the Illinois EPA, in 2013 we performed a geotechnical study at Vermilion and began a 12-month geotechnical/hydraulic/hydrogeologic study needed to analyze corrective action alternatives at Baldwin. The geotechnical study at Vermilion confirmed that the cap closure option proposed in our corrective action plans for the north and old east CCR surface impoundments is technically feasible. In September 2014, the Illinois EPA requested additional analyses concerning the closure plans for the Vermilion old east and north CCR surface impoundments. Those analyses, if performed, are not anticipated to be completed until late 2015. In June 2014, we submitted the results of our evaluation at Baldwin to the Illinois EPA. Based on the results of that evaluation, we recommended to the Illinois EPA that the closure process for the Baldwin out-of-service east CCR surface impoundment begin and that a geotechnical investigation of the existing soil cap on the Baldwin out-of-service old east CCR surface impoundment be undertaken. In October 2014, we submitted a supplemental groundwater modeling report to the Illinois EPA that indicates no known offsite water supply wells will be impacted under the various Baldwin CCR surface impoundment closure scenarios modeled. At this time we cannot reasonably estimate the costs of resolving these groundwater issues, but resolution of these matters may cause us to incur significant costs that could have a material adverse effect on our financial condition, results of operations and cash flows.
	IPH Segment Groundwater. Hydrogeologic investigations of the CCR surface impoundments have been performed at the IPH segment facilities.  Groundwater monitoring results indicate that the CCR surface impoundments at each of the IPH segment facilities potentially impact onsite groundwater.
	In 2012, the Illinois EPA issued violation notices with respect to groundwater conditions at the Newton and Coffeen facilities’ CCR surface impoundments. In February 2013, the Illinois EPA provided written notice that it may pursue legal action with respect to each of these matters through referral to the Illinois Office of the Attorney General. In addition, in April 2015, we submitted an assessment monitoring report to the Illinois EPA concerning previously reported groundwater quality standard exceedances at the Newton facility’s active CCR landfill. The report identifies the Newton facility’s inactive unlined landfill as the likely source of the contamination and recommends various measures to minimize the effects of that source on the groundwater monitoring results of the active landfill. The Illinois EPA also has required assessment monitoring at the Duck Creek facility’s active CCR landfill, with the findings of that assessment, including proposed remedial action, if any, due in September 2015.
	In April 2013, Ameren Energy Resources Company filed a proposed site-specific rulemaking with the IPCB which, if approved, would provide for the systematic and eventual closure of its CCR surface impoundments that impact groundwater in exceedance of applicable groundwater standards. In October 2013, the Illinois EPA filed a proposed rulemaking with the IPCB that would establish processes governing monitoring, corrective action and closure of CCR surface impoundments at all power generating facilities in Illinois. The site-specific rulemaking, which now covers IPH CCR surface impoundments, has been stayed to allow the Illinois EPA proposed rulemaking to proceed.
	At this time we cannot reasonably estimate the costs or range of costs of resolving the IPH groundwater matters, but resolution of these matters may cause IPH to incur significant costs that could have a material adverse effect on its financial condition, results of operations and cash flows.
	Station Power Proceedings. On May 4, 2010, the U.S. Court of Appeals for the District of Columbia Circuit (the “D.C. Circuit”) vacated FERC’s acceptance of station power rules for the CAISO market and remanded the case for further proceedings at FERC. On August 30, 2010, FERC issued an Order on Remand (“remand order”) effectively disclaiming jurisdiction over how the states impose retail station power charges. Due to reservation-of-rights language in the California utilities’ state-jurisdictional station power tariffs, the California utilities have argued that FERC’s ruling requires California generators to pay state-imposed retail charges back to the date of enrollment by the facilities in the CAISO’s station power program. The remand order could impact FERC’s station power policies in all of the organized markets throughout the nation.
	On November 18, 2011, Pacific Gas and Electric Company (“PG&E”) filed with the CPUC, seeking authorization to begin charging generators station power charges, and to assess such charges retroactively. On August 15, 2014, the CPUC approved a Draft Resolution that orders retroactive charges to be assessed against generators dating back to August 30, 2010.  In March of 2015, Dynegy settled its total retroactive charges for station power with PG&E. We had previously accrued for this settlement.
	Other Commitments
	In conducting our operations, we have routinely entered into long-term commodity purchase and sale commitments, as well as agreements that commit future cash flow to the lease or acquisition of assets used in our businesses. These commitments have been typically associated with commodity supply arrangements, capital projects, reservation charges associated with firm transmission, transportation, storage and leases for office space, equipment, design and construction, plant sites, power generation assets and liquefied petroleum gas vessel charters. The following describes the more significant commitments outstanding at March 31, 2015.
	Contractual Service Agreements.  Contractual service agreements represent obligations with respect to long-term plant maintenance agreements. Recently we have undertaken several measures to restructure our existing maintenance agreements as well as negotiate new long-term maintenance service agreements with proven turbine service providers. The term of these agreements will be determined by the maintenance cycles of the respective facility. We currently estimate these agreements will be in effect for a period of 15 or more years. Either party can terminate the agreements based on certain events as specified in the contracts. As of March 31, 2015, our minimum obligation with respect to these agreements is limited to the termination payments, which are approximately $159 million and $214 million in the event all contracts are terminated by us or the counterparty, respectively.
	Coal Commitments.  During the three months ended March 31, 2015, we entered into three new contracts to purchase coal for our generation facilities from 2015 through 2020 with aggregate minimum commitments of $145 million. To the extent forecasted volumes have not been priced but are subject to a price collar structure, the obligations have been calculated using the minimum purchase price of the collar.
	Coal Transportation. During the three months ended March 31, 2015, we executed two new coal transportation contracts for our generation facilities from 2015 through 2027 with aggregate minimum commitments of $254 million.
	Charter Agreements. In addition, we are party to two charter agreements related to very large gas carriers (“VLGCs”) previously utilized in our former global liquids business. The primary term of one charter expired at the end of September 2013 but has been extended annually, through September 2016, at the option of the counterparty. The primary term of the second charter was through September 2014 but has been extended through September 2016 at the option of the counterparty. The first charter will terminate at the end of September 2016, and the second charter has one optional one-year extension remaining. Both of these VLGCs have been sub-chartered to a wholly-owned subsidiary of Transammonia Inc. on terms that are identical to the terms of the original charter agreements. The aggregate minimum base commitments of the charter party agreements are approximately $11 million for each of the years ended December 31, 2015 and 2016. To date, the subsidiary of Transammonia Inc. has complied with the terms of the sub-charter agreement and has not exercised the remaining optional extension.
	Indemnifications and Guarantees
	In the ordinary course of business, we routinely enter into contractual agreements that contain various representations, warranties, indemnifications and guarantees.  Examples of such agreements include, but are not limited to, service agreements, equipment purchase agreements, engineering and technical service agreements, asset sales agreements, and procurement and construction contracts.  Some agreements contain indemnities that cover the other party’s negligence or limit the other party’s liability with respect to third party claims, in which event we will effectively be indemnifying the other party.  Virtually all such agreements contain representations or warranties that are covered by indemnifications against the losses incurred by the other parties in the event such representations and warranties are false.  While there is always the possibility of a loss related to such representations, warranties, indemnifications and guarantees in our contractual agreements, and such loss could be significant, in most cases management considers the probability of loss to be remote.
	LS Power Indemnities. In connection with the transaction with LS Power we agreed in the purchase and sale agreement to indemnify LS Power against claims regarding any breaches in our representations and warranties and certain other potential liabilities. Even though Dynegy was discharged from any claims pursuant to the order confirming the Plan (the “Confirmation Order”), Dynegy Power Generation Inc., Dynegy Power, LLC (“DPC”), DMG and Dynegy Power Marketing, LLC remain jointly and severally liable for any indemnification claims.  Although certain of the indemnification obligations are indefinite, some have exceeded the survival period in the relevant transaction agreements or have exceeded the applicable statute of limitations. In addition, some of these indemnification obligations are subject to individual thresholds and/or maximum aggregate limits depending on the terms of the transaction agreement. We have accrued no amounts with respect to the indemnifications as of March 31, 2015 because none were probable of occurring, nor could they be reasonably estimated.
	EquiPower Acquisition. In connection with the ECP Purchase Agreement, the ECP Purchasers agreed to indemnify the ECP Sellers against claims regarding breaches in the covenants and representations and warranties of the ECP Purchasers and certain other potential liabilities. The indemnification obligations of the ECP Purchasers shall survive for one year for most covenants and representations and warranties of the ECP Purchasers, two years for fundamental representations, and indefinitely for certain other matters. The ECP Sellers shall, in the aggregate, not be entitled to indemnification in excess of $276 million. We have accrued no amounts with respect to this indemnification as of March 31, 2015 because none were probable of occurring, nor could they be reasonably estimated. Please read Note 15—Subsequent Events—Acquisitions for further discussion.
	Duke Midwest Acquisition. In connection with the Duke Midwest Purchase Agreement, Dynegy Resource I, LLC (“DRI”) agreed to indemnify Duke Energy against claims regarding breaches in the covenants and representations and warranties of DRI and certain other potential liabilities. The indemnification obligations of DRI shall survive for one year for most covenants and representations and warranties of DRI, three years for fundamental representations, 30 days after the applicable statute of limitations for certain tax matters, and indefinitely for certain other matters. We have accrued no amounts with respect to this indemnification as of March 31, 2015 because none were probable of occurring, nor could they be reasonably estimated. Dynegy has guaranteed, up to maximum liability of $2.80 billion, the obligations of DRI under the Duke Midwest Purchase Agreement and related Transition Services Agreement. Please read Note 15—Subsequent Events—Acquisitions for further discussion.
	Limited Guaranty. In connection with the acquisition of AER, Dynegy has provided a Limited Guaranty of certain obligations of IPH up to $25 million. Concurrently with the execution of the AER transaction agreement, Dynegy entered into the Limited Guaranty, capped at $25 million in favor of Ameren Corporation (“Ameren”), for a period of two years after the closing (subject to certain exceptions) with respect to IPH’s indemnification obligations and certain reimbursement obligations under the AER transaction agreement. We have accrued no amounts with respect to the guaranty as of March 31, 2015 because none were probable of occurring, nor could they be reasonably estimated.

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Note 10—Income Taxes
	We compute our quarterly taxes under the effective tax rate method based on applying an anticipated annual effective rate to our year-to-date income or loss, except for significant unusual or extraordinary transactions.  Income taxes for significant unusual or extraordinary transactions are computed and recorded in the period that the specific transaction occurs.
	As of March 31, 2015, we continued to maintain a valuation allowance against our net deferred tax assets as there was not sufficient evidence to overcome our historical cumulative losses to conclude that it is more-likely-than-not our net deferred tax assets can be realized in the future. We expect that a significant portion of the valuation allowance will be released in the second quarter of 2015 as a result of increased deferred tax liabilities related to the EquiPower Acquisition. Please read Note 15—Subsequent Events for further discussion.

Pension_and_Other_PostEmployme

Pension and Other Post-Employment Benefit Plans	3 Months Ended
	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Pension and Other Post-Employment Benefit Plans	Note 11—Pension and Other Post-Employment Benefit Plans
	We sponsor and administer defined benefit plans and defined contribution plans for the benefit of our employees and also provide other post-employment benefits to retirees who meet age and service requirements which are more fully described in Note 17—Employee Compensation, Savings, Pension and Other Post-Employment Benefit Plans in our Form 10-K.
	The components of net periodic benefit cost (gain) were as follows:
		Pension Benefits						Other Benefits
		Three Months Ended March 31,
	(amounts in millions)	2015			2014			2015			2014
	Service cost benefits earned during period	$	3		$	3		$	—		$	—
	Interest cost on projected benefit obligation	4			4			1			1
	Expected return on plan assets	(5		)	(5		)	(1		)	(1		)
	Amortization of:
	Prior service credit	—			—			(1		)	(1		)
	Net periodic benefit cost (gain)	$	2		$	2		$	(1	)	$	(1	)

Loss_Per_Share

Loss Per Share	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Loss Per Share	Note 12—Loss Per Share
	The basic and diluted loss per share from continuing operations attributable to our common stockholders during the three months ended March 31, 2015 and 2014 is shown in the following table. Please read Note 16—Capital Stock in our Form 10-K for further discussion.
			Three Months Ended March 31,
	(in millions, except per share amounts)		2015				2014
	Loss from continuing operations		$	(181	)		$	(37	)
	Less: Net income (loss) attributable to noncontrolling interest		(1		)		4
	Loss from continuing operations attributable to Dynegy Inc.		(180		)		(41		)
	Less: Dividends on preferred stock		5				—
	Loss from continuing operations attributable to Dynegy Inc. common stockholders		$	(185	)		$	(41	)
	Basic and diluted weighted-average shares (1)		124				100
	Basic and diluted loss per share from continuing operations attributable to Dynegy Inc. common stockholders (1)		$	(1.49	)		$	(0.41	)
	__________________________________________
	-1	Entities with a net loss from continuing operations are prohibited from including potential common shares in the computation of diluted per share amounts. Accordingly, we have utilized the basic shares outstanding amount to calculate both basic and diluted loss per share for the three months ended March 31, 2015 and 2014.
	The following potentially dilutive securities were not included in the computation of diluted per share amounts because the effect would be anti-dilutive:
			Three Months Ended March 31,
	(in millions of shares)		2015			2014
	Stock options		1.8			1.4
	Restricted stock units		1.2			1.2
	Performance stock units		0.6			0.3
	Warrants		15.6			15.6
	Series A 5.375% mandatory convertible preferred stock		12.7			—
	Total		31.9			18.5

Condensed_Consolidating_Financ

Condensed Consolidating Financial Information	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Condensed Consolidating Financial Information	Note 1—Basis of Presentation and Organization
	The accompanying unaudited consolidated financial statements have been prepared in accordance with the instructions to interim financial reporting as prescribed by the SEC. The year-end consolidated balance sheet data was derived from audited consolidated financial statements but does not include all disclosures required by the Generally Accepted Accounting Principles of the United States of America (“GAAP”).  The unaudited consolidated financial statements contained in this report include all material adjustments of a normal recurring nature that, in the opinion of management, are necessary for a fair presentation of the results for the interim periods. Certain prior period amounts in our consolidated financial statements have been reclassified to conform to current year presentation. These interim financial statements should be read together with the consolidated financial statements and notes thereto included in our annual report on Form 10-K for the year ended December 31, 2014, filed with the SEC on February 25, 2015, which we refer to as our “Form 10-K.” Unless the context indicates otherwise, throughout this report, the terms “Dynegy,” “the Company,” “we,” “us,” “our,” and “ours” are used to refer to Dynegy Inc. and its direct and indirect subsidiaries.
	Our current business operations are focused primarily on the unregulated power generation sector of the energy industry. We report the results of our power generation business as three segments in our unaudited consolidated financial statements: (i) the Coal segment (“Coal”), (ii) the IPH segment (“IPH”) and (iii) the Gas segment (“Gas”). Our consolidated financial results also reflect corporate-level expenses such as general and administrative expense, interest expense and income tax benefit (expense). All significant intercompany transactions have been eliminated. Please read Note 14—Segment Information for further discussion.
	IPH and its direct and indirect subsidiaries are organized into ring-fenced groups in order to maintain corporate separateness from Dynegy and its other subsidiaries. Certain of the entities in the IPH segment, including Illinois Power Generating Company (“Genco”), have an independent director whose consent is required for certain corporate actions, including material transactions with affiliates. Further, entities within the IPH segment present themselves to the public as separate entities.  They maintain separate books, records and bank accounts and separately appoint officers.  Furthermore, they pay liabilities from their own funds, conduct business in their own names and have restrictions on pledging their assets for the benefit of certain other persons.  These provisions restrict our ability to move cash out of these entities without meeting certain requirements as set forth in the governing documents.
	On April 1, 2015, we completed the acquisition of EquiPower Resources Corp. and Brayton Point Holdings, LLC from Energy Capital Partners for an aggregate base purchase price of approximately $3.35 billion in cash plus $100 million in common stock of Dynegy, subject to certain adjustments. On April 2, 2015, we completed the acquisition of Duke Energy’s commercial generation assets and retail business in the Midwest for a base purchase price of approximately $2.80 billion in cash, subject to certain adjustments. Please read Note 15—Subsequent Events for further discussion.
	Note 13—Condensed Consolidating Financial Information
	On May 20, 2013, Dynegy issued the Senior Notes, as further described in Note 8—Debt. On October 27, 2014, the Escrow Issuers, wholly-owned subsidiaries of Dynegy, issued the Notes as further described in Note 8—Debt. The 100 percent owned subsidiary guarantors, jointly, severally and unconditionally, guaranteed the payment obligations under the Senior Notes and Notes. Not all of Dynegy’s subsidiaries guarantee the Senior Notes and Notes including Dynegy’s indirect, wholly-owned subsidiary, IPH, which acquired AER and its subsidiaries on December 2, 2013.
	The following condensed consolidating financial statements present the financial information of (i) Dynegy (Parent), which is the parent and issuer of the Senior Notes, on a stand-alone, unconsolidated basis, (ii) Escrow Issuers, which are the finance company issuers of the Notes, (iii) the guarantor subsidiaries of Dynegy, (iv) the non-guarantor subsidiaries of Dynegy and (v) the eliminations necessary to arrive at the information for Dynegy on a consolidated basis.
	These statements should be read in conjunction with the unaudited consolidated financial statements and notes thereto of Dynegy. The supplemental condensed consolidating financial information has been prepared pursuant to the rules and regulations for condensed financial information and does not include all disclosures included in annual financial statements.
	For purposes of the condensed consolidating financial information, a portion of our intercompany receivable which we do not consider to be likely of settlement has been classified as equity as of March 31, 2015 and December 31, 2014.
	Condensed Consolidating Balance Sheet as of March 31, 2015
	(amounts in millions)
		Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	Current Assets
	Cash and cash equivalents	$	1,438		$	—		$	122		$	174		$	—		$	1,734
	Restricted cash	—			205			—			—			—			205
	Accounts receivable, net	15			—			615			163			(525		)	268
	Inventory	—			—			90			134			—			224
	Other current assets	17			7			127			75			—			226
	Total Current Assets	1,470			212			954			546			(525		)	2,657
	Property, Plant and Equipment, Net	—			—			2,781			446			—			3,227
	Other Assets
	Investment in affiliates	5,986			—			—			—			(5,986		)	—
	Other long-term assets	57			54			67			53			—			231
	Restricted cash	—			5,100			—			—			—			5,100
	Intercompany note receivable	11			—			—			—			(11		)	—
	Total Assets	$	7,524		$	5,366		$	3,802		$	1,045		$	(6,522	)	$	11,215
	Current Liabilities
	Accounts payable	$	114		$	260		$	159		$	240		$	(525	)	$	248
	Other current liabilities	71			166			155			180			—			572
	Total Current Liabilities	185			426			314			420			(525		)	820
	Long-term debt	1,275			5,100			—			702			—			7,077
	Intercompany note payable	3,042			—			—			11			(3,053		)	—
	Other long-term liabilities	186			—			109			188			—			483
	Total Liabilities	4,688			5,526			423			1,321			(3,578		)	8,380
	Stockholders’ Equity
	Dynegy Stockholders’ Equity	2,836			(160		)	6,421			(275		)	(5,986		)	2,836
	Intercompany note receivable	—			—			(3,042		)	—			3,042			—
	Total Dynegy Stockholders’ Equity	2,836			(160		)	3,379			(275		)	(2,944		)	2,836
	Noncontrolling interest	—			—			—			(1		)	—			(1		)
	Total Equity	2,836			(160		)	3,379			(276		)	(2,944		)	2,835
	Total Liabilities and Equity	$	7,524		$	5,366		$	3,802		$	1,045		$	(6,522	)	$	11,215
	Condensed Consolidating Balance Sheet as of December 31, 2014
	(amounts in millions)
		Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	Current Assets
	Cash and cash equivalents	$	1,642		$	—		$	54		$	174		$	—		$	1,870
	Restricted cash	—			113			—			—			—			113
	Accounts receivable, net	14			—			672			176			(592		)	270
	Inventory	—			—			88			120			—			208
	Other current assets	9			6			125			73			—			213
	Total Current Assets	1,665			119			939			543			(592		)	2,674
	Property, Plant and Equipment, Net	—			—			2,812			443			—			3,255
	Other Assets
	Investment in affiliates	6,133			—			—			—			(6,133		)	—
	Other long-term assets	46			47			53			57			—			203
	Restricted cash	—			5,100			—			—			—			5,100
	Intercompany note receivable	17			—			—			—			(17		)	—
	Total Assets	$	7,861		$	5,266		$	3,804		$	1,043		$	(6,742	)	$	11,232
	Current Liabilities
	Accounts payable	$	310		$	166		$	112		$	220		$	(592	)	$	216
	Other current liabilities	51			67			250			97			—			465
	Total Current Liabilities	361			233			362			317			(592		)	681
	Long-term debt	1,277			5,100			—			698			—			7,075
Intercompany note payable	3,042			—			—			17			(3,059		)	—
Other long-term liabilities	158			—			105			190			—			453
Total Liabilities	4,838			5,333			467			1,222			(3,651		)	8,209
Stockholders’ Equity
Dynegy Stockholders’ Equity	3,023			(67		)	6,379			(179		)	(6,133		)	3,023
Intercompany note receivable	—			—			(3,042		)	—			3,042			—
Total Dynegy Stockholders’ Equity	3,023			(67		)	3,337			(179		)	(3,091		)	3,023
Noncontrolling interest	—			—			—			—			—			—
Total Equity	3,023			(67		)	3,337			(179		)	(3,091		)	3,023
Total Liabilities and Equity	$	7,861		$	5,266		$	3,804		$	1,043		$	(6,742	)	$	11,232
Condensed Consolidating Statements of Operations for the Three Months Ended March 31, 2015
(amounts in millions)
	Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
Revenues	$	—		$	—		$	413		$	219		$	—		$	632
Cost of sales, excluding depreciation expense	—			—			(239		)	(138		)	—			(377		)
Gross margin	—			—			174			81			—			255
Operating and maintenance expense	—			—			(60		)	(51		)	—			(111		)
Depreciation expense	—			—			(56		)	(8		)	—			(64		)
General and administrative expense	(1		)	—			(17		)	(12		)	—			(30		)
Acquisition and integration costs	—			—			—			(90		)	—			(90		)
Operating income (loss)	(1		)	—			41			(80		)	—			(40		)
Equity in losses from investments in affiliates	(147		)	—			—			—			147			—
Interest expense	(27		)	(93		)	—			(16		)	—			(136		)
Other income and expense, net	(5		)	—			—			—			—			(5		)
Income (loss) before income taxes	(180		)	(93		)	41			(96		)	147			(181		)
Income tax expense	—			—			—			—			—			—
Net income (loss)	(180		)	(93		)	41			(96		)	147			(181		)
Less: Net loss attributable to noncontrolling interest	—			—			—			(1		)	—			(1		)
Net income (loss) attributable to Dynegy Inc.	$	(180	)	$	(93	)	$	41		$	(95	)	$	147		$	(180	)
Condensed Consolidating Statements of Operations for the Three Months Ended March 31, 2014
(amounts in millions)
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
Revenues	$	—		$	558		$	204		$	—		$	762
Cost of sales, excluding depreciation expense	—			(393		)	(159		)	—			(552		)
Gross margin	—			165			45			—			210
Operating and maintenance expense	—			(63		)	(47		)	—			(110		)
Depreciation expense	—			(59		)	(8		)	—			(67		)
General and administrative expense	(2		)	(14		)	(10		)	—			(26		)
Acquisition and integration costs	—			—			(6		)	—			(6		)
Operating income (loss)	(2		)	29			(26		)	—			1
Equity in losses from investments in affiliates	(39		)	—			—			39			—
Interest expense	(16		)	—			(14		)	—			(30		)
Other income and expense, net	(6		)	—			—			—			(6		)
Income (loss) before income taxes	(63		)	29			(40		)	39			(35		)
Income tax benefit (expense)	22			—			(24		)	—			(2		)
Net income (loss)	(41		)	29			(64		)	39			(37		)
Less: Net income attributable to noncontrolling interest	—			—			4			—			4
Net income (loss) attributable to Dynegy Inc.	$	(41	)	$	29		$	(68	)	$	39		$	(41	)
Condensed Consolidating Statements of Comprehensive Income (Loss) for the Three Months Ended March 31, 2015
(amounts in millions)
	Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
Net income (loss)	$	(180	)	$	(93	)	$	41		$	(96	)	$	147		$	(181	)
Amounts reclassified from accumulated other comprehensive income:
Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	(1		)	—			—			—			—			(1		)
Other comprehensive loss, net of tax	(1		)	—			—			—			—			(1		)
Comprehensive income (loss)	(181		)	(93		)	41			(96		)	147			(182		)
Less: Comprehensive loss attributable to noncontrolling interest	—			—			—			(1		)	—			(1		)
Total comprehensive income (loss) attributable to Dynegy Inc.	$	(181	)	$	(93	)	$	41		$	(95	)	$	147		$	(181	)
Condensed Consolidating Statements of Comprehensive Income (Loss) for the Three Months Ended March 31, 2014
(amounts in millions)
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
Net income (loss)	$	(41	)	$	29		$	(64	)	$	39		$	(37	)
Other comprehensive income (loss) before reclassifications:
Actuarial loss, net of tax of zero	—			—			(3		)	—			(3		)
Amounts reclassified from accumulated other comprehensive income:
Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	(1		)	—			—			—			(1		)
Other comprehensive income (loss) from investment in affiliates	(3		)	—			—			3			—
Other comprehensive income (loss), net of tax	(4		)	—			(3		)	3			(4		)
Comprehensive income (loss)	(45		)	29			(67		)	42			(41		)
Less: Comprehensive income (loss) attributable to noncontrolling interest	(1		)	—			3			1			3
Total comprehensive income (loss) attributable to Dynegy Inc.	$	(44	)	$	29		$	(70	)	$	41		$	(44	)
Condensed Consolidating Statements of Cash Flow for the Three Months Ended March 31, 2015
(amounts in millions)
	Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	$	2		$	(94	)	$	46		$	(9	)	$	—		$	(55	)
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	—			—			(29		)	(11		)	—			(40		)
Net intercompany transfers	(188		)	—			—			—			188			—
Net cash provided by (used in) investing activities	(188		)	—			(29		)	(11		)	188			(40		)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of borrowings	(2		)	—			(23		)	—			—			(25		)
Dividends paid	(7		)	—			—			—			—			(7		)
Net intercompany transfers	—			94			74			20			(188		)	—
Interest rate swap settlement payments	(4		)	—			—			—			—			(4		)
Other financing	(5		)	—			—			—			—			(5		)
Net cash provided by (used in) financing activities	(18		)	94			51			20			(188		)	(41		)
Net increase (decrease) in cash and cash equivalents	(204		)	—			68			—			—			(136		)
Cash and cash equivalents, beginning of period	1,642			—			54			174			—			1,870
Cash and cash equivalents, end of period	$	1,438		$	—		$	122		$	174		$	—		$	1,734
Condensed Consolidating Statements of Cash Flow for the Three Months Ended March 31, 2014
(amounts in millions)
	Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	$	(9	)	$	140		$	35		$	—		$	166
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	—			(6		)	(11		)	—			(17		)
Net intercompany transfers	113			—			—			(113		)	—
Net cash provided by (used in) investing activities	113			(6		)	(11		)	(113		)	(17		)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from long-term borrowings, net of financing costs	(1		)	12			—			—			11
Repayments of borrowings	(2		)	—			—			—			(2		)
Net intercompany transfers	—			(142		)	29			113			—
Interest rate swap settlement payments	(4		)	—			—			—			(4		)
Other financing	(1		)	—			—			—			(1		)
Net cash provided by (used in) financing activities	(8		)	(130		)	29			113			4
Net increase in cash and cash equivalents	96			4			53			—			153
Cash and cash equivalents, beginning of period	474			154			215			—			843
Cash and cash equivalents, end of period	$	570		$	158		$	268		$	—		$	996

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Information	Note 14—Segment Information
	We report the results of our operations in three segments: (i) Coal, (ii) IPH and (iii) Gas. The Coal segment includes DMG, which owns, directly and indirectly, certain of our coal-fired power generation facilities, and our Dynegy Energy Services retail business. The IPH segment includes Genco, and Illinois Power Resources Generating, LLC (“IPRG”) which also own, directly and indirectly, certain of our coal-fired power generation facilities. IPH also includes our Homefield Energy retail business in Illinois. IPH and its direct and indirect subsidiaries and Genco and its direct and indirect subsidiaries are each organized into ring-fenced groups in order to maintain corporate separateness. The Gas segment includes DPC, which owns, directly or indirectly, substantially all of our natural gas-fired power generation facilities. Our consolidated financial results also reflect corporate-level expenses such as general and administrative expense, interest expense and income tax benefit (expense). General and administrative expense is reported in Other for all periods presented.
	Reportable segment information, including intercompany transactions accounted for at prevailing market rates, for the three months ended March 31, 2015 and 2014 is presented below:
	Segment Data as of and for the Three Months Ended March 31, 2015
	(amounts in millions)	Coal			IPH			Gas			Other and			Total
											Eliminations
	Domestic:
	Unaffiliated revenues	$	143		$	219		$	270		$	—		$	632
	Intercompany revenues	(1		)	—			1			—			—
	Total revenues	$	142		$	219		$	271		$	—		$	632
	Depreciation expense	$	(10	)	$	(8	)	$	(45	)	$	(1	)	$	(64	)
	General and administrative expense	—			—			—			(30		)	(30		)
	Acquisition and integration costs	—			—			—			(90		)	(90		)
	Operating income (loss)	$	7		$	22		$	52		$	(121	)	$	(40	)
	Interest expense										(136		)	(136		)
	Other income and expense, net	—			—			—			(5		)	(5		)
	Loss before income taxes													(181		)
	Income tax expense										—			—
	Net loss													(181		)
	Less: Net loss attributable to noncontrolling interest													(1		)
	Net loss attributable to Dynegy Inc.													$	(180	)
	Identifiable assets (domestic)	$	1,162		$	1,037		$	2,105		$	6,911		$	11,215
	Capital expenditures	$	(3	)	$	(11	)	$	(24	)	$	(2	)	$	(40	)
	Segment Data as of and for the Three Months Ended March 31, 2014
	(amounts in millions)	Coal			IPH			Gas			Other and			Total
											Eliminations
	Domestic:
	Unaffiliated revenues	$	161		$	203		$	398		$	—		$	762
	Intercompany revenues	(5		)	1			4			—			—
	Total revenues	$	156		$	204		$	402		$	—		$	762
	Depreciation expense	$	(14	)	$	(8	)	$	(44	)	$	(1	)	$	(67	)
	General and administrative expense	—			—			—			(26		)	(26		)
	Operating income (loss)	$	9		$	(16	)	$	34		$	(26	)	$	1
	Interest expense										(30		)	(30		)
	Other income and expense, net	—			—			—			(6		)	(6		)
	Loss before income taxes													(35		)
	Income tax expense										(2		)	(2		)
	Net loss													(37		)
	Less: Net income attributable to noncontrolling interest													4
	Net loss attributable to Dynegy Inc.													$	(41	)
	Identifiable assets (domestic)	$	1,198		$	1,203		$	2,202		$	749		$	5,352
	Capital expenditures	$	(3	)	$	(11	)	$	(2	)	$	(1	)	$	(17	)

Subsequent_Events

Subsequent Events	3 Months Ended
	Mar. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	Note 15—Subsequent Events
	Acquisitions
	ECP and ERC Purchase Agreements. On April 1, 2015 (the “EquiPower Closing Date”), pursuant to the terms of the stock purchase agreement dated August 21, 2014, as amended (the “ERC Purchase Agreement”), by and among our wholly-owned subsidiary, Dynegy Resource II, LLC (“ERC Purchaser”) and Energy Capital Partners II, LP (“ECP II”), Energy Capital Partners II-A, LP (“ECP II-A”), Energy Capital Partners II-B, LP (“ECP II-B”), Energy Capital Partners II-C (Direct IP), LP (“ECP II-C”), Energy Capital Partners II-D, LP (“ECP II-D”), and Energy Capital Partners II (EquiPower Co-Invest), LP (“ECP Coinvest” and, collectively with ECP II, ECP II-A, ECP II-B, ECP II-C and ECP II-D, the “ERC Sellers”), EquiPower Resources Corp. (“ERC”), and solely for certain limited purposes set forth therein, each of Energy Capital Partners II-C, LP (“ECP II-C Fund”), and Dynegy, pursuant to which the ERC Purchaser, subject to the terms and conditions in the ERC Purchase Agreement, purchased from the ERC Sellers 100 percent of the equity interests in ERC, thereby acquiring (i) five combined cycle natural gas-fired facilities in Connecticut, Massachusetts and Pennsylvania, (ii) a partial interest in one natural gas-fired peaking facility in Illinois, (iii) two gas and oil-fired peaking facilities in Ohio and (iv) one coal-fired facility in Illinois (the “ERC Acquisition”).
	On the EquiPower Closing Date, in a related transaction, pursuant to a stock purchase agreement and plan of merger dated August 21, 2014, as amended (the “Brayton Purchase Agreement” and, together with the ERC Purchase Agreement, the “ECP Purchase Agreement”), by and among our wholly-owned subsidiaries, Dynegy Resource III, LLC (the “Brayton Purchaser” and, together with the ERC Purchaser, the “ECP Purchasers”), and Dynegy Resource III-A, LLC, the (“Merger Sub”), and Energy Capital Partners GP II, LP (“ECP GP”), ECP II, ECP II-A, ECP II-B, ECP II-D, and Energy Capital Partners II-C (Cayman), L.P. (“ECP II-C (Cayman)” and, collectively with ECP GP, ECP II, ECP II-A, ECP II-B and ECP II-D, the “Brayton Sellers” and, together with the ERC Sellers, the “ECP Sellers”), Brayton Point Holdings, LLC (“Brayton”), and, solely for certain limited purposes set forth therein, each of ECP II-C Fund and Dynegy, pursuant to which Brayton Purchaser purchased from Brayton Sellers and other holders of equity interests in Brayton, through a stock purchase and the related merger of Merger Sub with and into Brayton, 100 percent of the equity interests in Brayton, a coal-fired facility in Massachusetts, (the “Brayton Acquisition”).
	The ERC Acquisition and the Brayton Acquisition (collectively, the “EquiPower Acquisition”) added approximately 6,300 MW of generation in Connecticut, Illinois, Massachusetts, Ohio and Pennsylvania for an aggregate base purchase price of approximately $3.35 billion in cash plus $100 million in common stock of Dynegy, subject to certain adjustments.
	Under the ECP Purchase Agreement, the ECP Purchaser and ECP Sellers have agreed to indemnify the other applicable parties for breaches of representations and warranties, breaches of covenants and certain other matters, subject to certain exceptions and limitations.  Neither the ECP Purchasers nor the ECP Sellers, in the aggregate, are entitled to indemnification in excess of $276 million, and $104 million of the purchase price will be held in escrow for one year after closing to support the post-closing adjustment and the indemnification obligations of the ECP Sellers.
	Duke Midwest Purchase Agreement. On April 2, 2015 (the “Duke Midwest Closing Date”), pursuant to the terms of the purchase and sale agreement dated August 21, 2014, as amended (the “Duke Midwest Purchase Agreement”), by and among our wholly-owned subsidiary, DRI, and Duke Energy SAM, LLC (“Duke Energy SAM”) and Duke Energy Commercial Enterprises, Inc. (“Duke Energy CE” and, together with Duke Energy SAM, “Duke Energy”), DRI purchased from Duke Energy 100 percent of the membership interests in Duke Energy Commercial Asset Management, LLC and Duke Energy Retail Sales, LLC, thereby acquiring approximately 6,200 MW of generation in (i) five natural gas-fired power facilities located in Ohio, Pennsylvania and Illinois, (ii) one oil-fired power facility located in Ohio, (iii) partial interests in five coal-fired power facilities located in Ohio and (iv) a retail energy business for a base purchase price of approximately $2.80 billion in cash, subject to certain adjustments (the “Duke Midwest Acquisition” and, together with the EquiPower Acquisition, the “Acquisitions”). We will operate two of the five coal-fired facilities, the Miami Fort and Zimmer facilities, with other owners operating the three remaining facilities.
	Under the Duke Midwest Purchase Agreement, DRI and Duke Energy have agreed to indemnify the other applicable parties for breaches of representations and warranties, breaches of covenants and certain other matters, subject to certain exceptions and limitations.  Dynegy has guaranteed, up to a maximum liability of $2.80 billion, the obligations of DRI under the Duke Midwest Purchase Agreement and related Transition Services Agreement. DRI shall, in the aggregate, not be entitled to indemnification in excess of $280 million for most matters and $2.80 billion for certain fundamental representations, tax matters and fraud.
	Business Combination Accounting. In connection with our purchase price allocation, we are currently in the process of valuing the assets acquired and liabilities assumed in the Acquisitions. We are currently unable to provide pro forma financial results or the amounts recognized as of the respective acquisition dates for the major classes of assets acquired and liabilities assumed in the Acquisitions. We will provide these disclosures in our quarterly report on Form 10-Q for the second quarter of 2015.
	Acquisition Financing
	Credit Agreement Amendments. On the EquiPower Closing Date, Dynegy entered into a First Amendment to the Credit Agreement (the “First Amendment”) among Dynegy, certain subsidiaries of Dynegy, the lenders party thereto, Credit Suisse AG, Cayman Islands Branch (“Credit Suisse”), as administrative agent, and the other parties thereto.  The First Amendment provides for a new $350 million five-year senior secured incremental tranche of revolving commitments (the “Incremental Tranche A Revolving Loan Commitments”), which have terms substantially the same as the terms of the outstanding tranche of revolving loans under the Credit Agreement and will mature on April 1, 2020.  Amounts available under the Incremental Tranche A Revolving Loan Commitments are available on a revolving basis, and such amounts that are repaid or prepaid may be re-borrowed. The loans issued pursuant to the Incremental Tranche A Revolving Loan Commitments bear interest, initially, at either (i) 2.75 percent per annum plus LIBOR with respect to any LIBOR Loan or (ii) 1.75 percent per annum plus the Base Rate with respect to any Base Rate Loan, with steps down based on a Senior Secured Leverage Ratio (as such terms are defined in the Credit Agreement).
	Further on the Duke Midwest Closing Date, Dynegy entered into a Second Amendment to the Credit Agreement (the “Second Amendment”) among the Company, certain subsidiaries of Dynegy, the lenders party thereto, Credit Suisse, as administrative agent, and the other parties thereto. The Second Amendment provides for a new $600 million five-year senior secured incremental tranche of revolving commitments (the “Incremental Tranche B Revolving Loan Commitments”), which have terms substantially the same as the terms of the outstanding tranche of revolving loans under the Credit Agreement and will mature on April 2, 2020.  Amounts available under the Incremental Tranche B Revolving Loan Commitments are available on a revolving basis, and such amounts that are repaid or prepaid may be re-borrowed. The loans issued pursuant to the Incremental Tranche B Revolving Loan Commitments bear interest, initially, at either (i) 2.75 percent per annum plus LIBOR with respect to any LIBOR Loan or (ii) 1.75 percent per annum plus the Base Rate with respect to any Base Rate Loan, with steps down based on a Senior Secured Leverage Ratio (as such terms are defined in the Credit Agreement).
	Acquisition Debt Issuance. On October 27, 2014, Dynegy Finance II, Inc. (the “EquiPower Escrow Issuer”), a wholly-owned subsidiary of Dynegy, issued $3.06 billion in aggregate principal amount of senior notes, the proceeds of which were placed into escrow until the closing of the EquiPower Acquisition.  On the EquiPower Closing Date, the proceeds from the issuance were released from escrow and used to pay a portion of the EquiPower Acquisition consideration and to pay fees and expenses. On the EquiPower Closing Date, Dynegy, as successor in interest to the EquiPower Escrow Issuer, executed supplemental indentures evidencing its accession to the 6.75 percent senior notes due 2019 (the “2019 Finance II Notes”), the 7.375 percent senior notes due 2022 (the “2022 Finance II Notes”), and the 7.625 percent senior notes due 2024 (the “2024 Finance II Notes” and, together with the 2019 Finance II Notes and the 2022 Finance II Notes, the “Finance II Notes”).
	Further, on October 27, 2014, Dynegy Finance I, Inc. (the “Duke Escrow Issuer”), a wholly-owned subsidiary of Dynegy, issued $2.04 billion in aggregate principal amount of senior notes, the proceeds of which were placed into escrow until the closing of the Duke Midwest Acquisition.  On the Duke Midwest Closing Date, the proceeds from the issuance were released from escrow and used to pay a portion of the Duke Midwest Acquisition consideration and to pay fees and expenses. On the Duke Midwest Closing Date, Dynegy, as successor in interest to the Duke Escrow Issuer, executed supplemental indentures evidencing its accession to the 6.75 percent senior notes due 2019 (the “2019 Finance I Notes”), the 7.375 percent senior notes due 2022 (the “2022 Finance I Notes”), and the 7.625 percent senior notes due 2024 (the “2024 Finance I Notes” and, together with the 2019 Finance I Notes and the 2022 Finance I Notes, the “Finance I Notes”). Concurrently with Dynegy’s accession to the Finance I Notes, as successor in interest to the Duke Escrow Issuer, each series of Finance I Notes was automatically exchanged for an equal aggregate principal amount of Finance II Notes with the same terms, as applicable, issued by Dynegy. The additional Finance II Notes issued pursuant to such automatic exchanges were treated as a single class for all purposes and are fully fungible with the Finance II Notes with the same terms previously issued under the Finance II indentures.
	The following table sets forth the debt assumed by Dynegy following the EquiPower Closing Date and the Duke Midwest Closing Date:
	(amounts in millions)	2-Apr-15
	Dynegy Inc.:
	6.75% Senior Notes, due 2019	$	2,100
	7.375% Senior Notes, due 2022	$	1,750
	7.625% Senior Notes, due 2024	$	1,250
	On the EquiPower Closing Date, generally, each of Dynegy’s current wholly-owned domestic subsidiaries that is a borrower or guarantor under Dynegy’s existing credit facilities (the “Dynegy Guarantors”), and the entities acquired in the EquiPower Acquisition (the “EquiPower Guarantors”) executed supplemental indentures evidencing their accession to the Finance II Notes as guarantors. Similarly, on the Duke Midwest Closing Date, each of Dynegy’s current wholly-owned domestic subsidiaries that is a borrower or guarantor under Dynegy’s existing credit facilities and the entities acquired in the Duke Midwest Acquisition (the “Duke Guarantors”) executed supplemental indentures evidencing their accession to the Finance I Notes and the Finance II Notes as guarantors.
	On the EquiPower Closing Date, the Dynegy Guarantors and the EquiPower Guarantors executed a joinder to the registration rights agreement, dated October 27, 2014, among the EquiPower Escrow Issuer, the Duke Escrow Issuer, and Morgan Stanley & Co. LLC, Barclays Capital Inc., Credit Suisse Securities (USA) LLC, RBC Capital Markets, LLC and UBS Securities LLC as representatives of the initial purchasers identified therein (the “Registration Rights Agreement”).  Additionally, on the Duke Midwest Closing Date, the Duke Guarantors executed a joinder to the Registration Rights Agreement.
	Senior Notes
	On the respective closing dates, Dynegy executed a second and third supplemental indenture adding the EquiPower Guarantors and the Duke Guarantors as guarantors of the $500 million in aggregate principal amount of the Senior Notes.
	Dividends
	On March 3, 2015, our Board of Directors declared a dividend on our Mandatory Convertible Preferred Stock of $1.34 per share, or approximately $5 million in the aggregate. The dividend is for the dividend period beginning on February 1, 2015 and ending on April 30, 2015. Such dividends were paid on May 1, 2015 to stockholders of record as of April 15, 2015.

Accounting_Policies_Policies

Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited consolidated financial statements have been prepared in accordance with the instructions to interim financial reporting as prescribed by the SEC. The year-end consolidated balance sheet data was derived from audited consolidated financial statements but does not include all disclosures required by the Generally Accepted Accounting Principles of the United States of America (“GAAP”).  The unaudited consolidated financial statements contained in this report include all material adjustments of a normal recurring nature that, in the opinion of management, are necessary for a fair presentation of the results for the interim periods. Certain prior period amounts in our consolidated financial statements have been reclassified to conform to current year presentation. These interim financial statements should be read together with the consolidated financial statements and notes thereto included in our annual report on Form 10-K for the year ended December 31, 2014, filed with the SEC on February 25, 2015, which we refer to as our “Form 10-K.” Unless the context indicates otherwise, throughout this report, the terms “Dynegy,” “the Company,” “we,” “us,” “our,” and “ours” are used to refer to Dynegy Inc. and its direct and indirect subsidiaries.
	Our current business operations are focused primarily on the unregulated power generation sector of the energy industry. We report the results of our power generation business as three segments in our unaudited consolidated financial statements: (i) the Coal segment (“Coal”), (ii) the IPH segment (“IPH”) and (iii) the Gas segment (“Gas”). Our consolidated financial results also reflect corporate-level expenses such as general and administrative expense, interest expense and income tax benefit (expense). All significant intercompany transactions have been eliminated. Please read Note 14—Segment Information for further discussion.
	IPH and its direct and indirect subsidiaries are organized into ring-fenced groups in order to maintain corporate separateness from Dynegy and its other subsidiaries. Certain of the entities in the IPH segment, including Illinois Power Generating Company (“Genco”), have an independent director whose consent is required for certain corporate actions, including material transactions with affiliates. Further, entities within the IPH segment present themselves to the public as separate entities.  They maintain separate books, records and bank accounts and separately appoint officers.  Furthermore, they pay liabilities from their own funds, conduct business in their own names and have restrictions on pledging their assets for the benefit of certain other persons.  These provisions restrict our ability to move cash out of these entities without meeting certain requirements as set forth in the governing documents.
Use of Estimates	The preparation of consolidated financial statements in conformity with GAAP requires management to make informed estimates and judgments that affect our reported financial position and results of operations based on currently available information.  Actual results could differ materially from our estimates. The results of operations for the interim periods presented in this Form 10-Q are not necessarily indicative of the results to be expected for the full year or any other interim period due to seasonal fluctuations in demand for our energy products and services, changes in commodity prices, timing of maintenance and other expenditures and other factors.
Accounting Standards Adopted During the Current Period	Accounting Standards Adopted During the Current Period
	Reporting Discontinued Operations and Asset Disposals. In April 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-08-Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosure of Disposals of Components of an Entity. The amendments in this ASU change the requirements for reporting discontinued operations in Subtopic 205-20. An entity is required to report within discontinued operations on the statement of operations the results of a component or group of components of an entity if the disposal represents a strategic shift that has, or will have, a major effect on an entity’s operations and financial results. Additionally, the associated assets and liabilities are required to be presented separately from other assets and liabilities on the balance sheet for all comparative periods. The ASU includes updated guidance regarding what meets the definition of a component of an entity. The new financial statement presentation provisions relating to this ASU are prospective and effective for interim and annual periods beginning after December 15, 2014, with early adoption permitted. The adoption of this ASU did not have a material impact on our financial statements or disclosures.
Accounting Standards Not Yet Adopted	Accounting Standards Not Yet Adopted
	Debt Issuance Costs. In April 2015, the FASB issued ASU 2015-03-Interest-Imputation of Interest (Subtopic 835-30).  The amendments in this ASU require that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts.  The recognition and measurement guidance for debt issuance costs are not affected by the amendments in this update.  The guidance in this ASU is effective for interim and annual periods beginning after December 15, 2015, with early adoption permitted.  The adoption of this ASU should be applied on a retrospective basis, affecting all balance sheet periods presented.  We do not anticipate the adoption of this ASU will have a material impact on the presentation of our consolidated balance sheets.
	Consolidation. In February 2015, the FASB issued ASU 2015-02-Consolidation (Topic 810). The amendments in this ASU respond to concerns about the current accounting for consolidation of certain legal entities, in particular: (i) consolidation of limited partnerships and similar legal entities, (ii) evaluating fees paid to a decision maker or a service provider as a variable interest, (iii) the effect of fee arrangements on the primary beneficiary determination, (iv) the effect of related parties on the primary beneficiary determination and (v) consolidation of certain investment funds. The guidance in this ASU is effective for interim and annual periods beginning after December 15, 2015, with early adoption permitted in an interim period. We do not anticipate the adoption of this ASU will have a material impact on our consolidated financial statements.
	Extraordinary and Unusual Items. In January 2015, the FASB issued ASU 2015-01-Income Statement-Extraordinary and Unusual Items (Subtopic 225-20). The amendments in this ASU eliminate from GAAP the concept of extraordinary items and will no longer require separate classification of them within the statement of operations. Presentation and disclosure guidance for items that are unusual in nature or occur infrequently will be retained and will be expanded to include items that are both unusual in nature and infrequently occurring. The guidance in this ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015.  Reporting entities may elect to apply the amendments prospectively only, or retrospectively for all prior periods presented in the financial statements.  Early adoption is permitted provided that the guidance is applied from the beginning of the fiscal year of adoption. We do not anticipate the adoption of this ASU will have a material impact on our consolidated financial statements.
	Revenue from Contracts with Customers. In May 2014, the FASB and International Accounting Standards Board (“IASB”) jointly issued ASU 2014-09-Revenue from Contracts with Customers (Topic 606). The amendments in this ASU develop a common revenue standard for GAAP and International Financial Reporting Standards (“IFRS”) by removing inconsistencies and weaknesses in revenue requirements, providing a more robust framework for addressing revenue issues, improving comparability of revenue recognition practices, providing more useful information to users of financial statements and simplifying the preparation of financial statements. The guidance in this ASU is effective for interim and annual periods beginning after December 15, 2017, with early adoption permitted for interim and annual periods beginning after December 15, 2016. We are currently assessing this ASU; however, we do not anticipate the adoption of this ASU will have a material impact on our consolidated financial statements.

Risk_Management_Activities_Der1

Risk Management Activities, Derivatives and Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Contracts and Interest Rate Swaps	As of March 31, 2015, we had net purchases and sales of derivative contracts outstanding in the following quantities:
	Contract Type		Quantity			Unit of Measure		Fair Value (1)
	(dollars and quantities in millions)		Purchases (Sales)					Asset (Liability)
	Commodity contracts:
	Electricity derivatives (2)		(18	)		MWh		$	80
	Electricity basis derivatives (3)		(12	)		MWh		$	(6	)
	Natural gas derivatives (2)		85			MMBtu		$	(81	)
	Natural gas basis derivatives		22			MMBtu		$	(2	)
	Diesel fuel derivatives		6			Gallon		$	(5	)
	Coal derivatives		—			Metric Ton		$	(1	)
	Crude oil derivatives		—			Barrel		$	(2	)
	Emissions derivatives		5			Metric Ton		$	1
	Interest rate swaps		783			U.S. Dollar		$	(49	)
	Common stock warrants (4)		16			Warrant		$	(66	)
	__________________________________________
	-1	Includes both asset and liability risk management positions, but excludes margin and collateral netting of $2 million.
	-2	Mainly comprised of swaps, options and physical forwards.
	-3	Comprised of FTRs and swaps.
	-4	Each warrant is convertible into one share of Dynegy common stock.
Schedule of Derivative Instruments in the Balance Sheet, Fair Value	The following tables present the fair value and balance sheet classification of derivatives in the unaudited consolidated balance sheets as of March 31, 2015 and December 31, 2014. As of March 31, 2015 and December 31, 2014, there were no gross amounts available to be offset that were not offset in our unaudited consolidated balance sheets.
						March 31, 2015
										Gross amounts offset in the balance sheet
	Contract Type			Balance Sheet Location		Gross Fair Value				Contract Netting			Collateral or Margin Received or Paid		Net Fair Value
	(amounts in millions)
	Derivative assets:
		Commodity contracts		Assets from risk management activities		$	118			$	(34	)	$		$	84
		Total derivative assets				$	118			$	(34	)	$	—	$	84
	Derivative liabilities:
		Commodity contracts		Liabilities from risk management activities		$	(134	)		$	34		$	2	$	(98	)
		Interest rate contracts		Liabilities from risk management activities		(49		)		—			—		(49		)
		Common stock warrants		Other long-term liabilities		(66		)		—			—		(66		)
		Total derivative liabilities				$	(249	)		$	34		$	2	$	(213	)
	Total derivatives					$	(131	)		$	—		$	2	$	(129	)
						31-Dec-14
										Gross amounts offset in the balance sheet
	Contract Type			Balance Sheet Location		Gross Fair Value				Contract Netting			Collateral or Margin Received or Paid		Net Fair Value
	(amounts in millions)
	Derivative assets:
		Commodity contracts		Assets from risk management activities		$	115			$	(35	)	$	—	$	80
		Total derivative assets				$	115			$	(35	)	$	—	$	80
	Derivative liabilities:
		Commodity contracts		Liabilities from risk management activities		$	(163	)		$	35		$	9	$	(119	)
		Interest rate contracts		Liabilities from risk management activities		(44		)		—			—		(44		)
		Common stock warrants		Other long-term liabilities		(61		)		—			—		(61		)
		Total derivative liabilities				$	(268	)		$	35		$	9	$	(224	)
	Total derivatives					$	(153	)		$	—		$	9	$	(144	)
Schedule of Derivative Collateral Posted and Location on Balance Sheet	The following table summarizes our total cash collateral posted as of March 31, 2015 and December 31, 2014, along with the location on the balance sheet and the amount applied against our short-term risk management liabilities.
	Location on balance sheet		31-Mar-15				31-Dec-14
	(amounts in millions)
	Gross collateral posted with counterparties		$	59			$	49
	Less: Collateral netted against risk management liabilities		2				9
	Net collateral within Prepayments and other current assets		$	57			$	40
Schedule of Derivative Instruments, Gain (Loss) in the Statement of Operations	The recognized impact of derivative financial instruments on our unaudited consolidated statements of operations for the three months ended March 31, 2015 and 2014 is presented below.
	Derivatives Not Designated as Hedges		Location of Gain (Loss)		Three Months Ended March 31,
			Recognized in Income on
			Derivatives		2015				2014
	(amounts in millions)
	Commodity contracts		Revenues		$	19			$	(173	)
	Interest rate contracts		Interest expense		$	(9	)		$	3
	Common stock warrants		Other income (expense), net		$	(5	)		$	(6	)

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables set forth, by level within the fair value hierarchy, our financial assets and liabilities that were accounted for at fair value on a recurring basis as of March 31, 2015 and December 31, 2014 and are presented on a gross basis before consideration of amounts netted under master netting agreements and the application of collateral and margin paid.
			Fair Value as of March 31, 2015
	(amounts in millions)		Level 1				Level 2				Level 3				Total
	Assets:
	Assets from commodity risk management activities:
	Electricity derivatives		$	—			$	96			$	17			$	113
	Natural gas derivatives		—				4				—				4
	Emissions derivatives		—				1				—				1
	Total assets from commodity risk management activities		$	—			$	101			$	17			$	118
	Liabilities:														.
	Liabilities from commodity risk management activities:
	Electricity derivatives		$	—			$	(26	)		$	(13	)		$	(39	)
	Natural gas derivatives		—				(87		)		—				(87		)
	Diesel fuel derivatives		—				(5		)		—				(5		)
	Crude oil derivatives		—				(2		)		—				(2		)
	Coal derivatives		—				(1		)		—				(1		)
	Total liabilities from commodity risk management activities		—				(121		)		(13		)		(134		)
	Liabilities from interest rate contracts		—				(49		)		—				(49		)
	Liabilities from outstanding common stock warrants		(66		)		—				—				(66		)
	Total liabilities		$	(66	)		$	(170	)		$	(13	)		$	(249	)
			Fair Value as of December 31, 2014
	(amounts in millions)		Level 1				Level 2				Level 3				Total
	Assets:
	Assets from commodity risk management activities:
	Electricity derivatives		$	—			$	88			$	22			$	110
	Natural gas derivatives		—				3				—				3
	Emissions derivatives		—				2				—				2
	Total assets from commodity risk management activities		$	—			$	93			$	22			$	115
	Liabilities:
	Liabilities from commodity risk management activities:
	Electricity derivatives		$	—			$	(27	)		$	(26	)		$	(53	)
	Natural gas derivatives		—				(100		)		—				(100		)
	Diesel derivatives		—				(6		)		—				(6		)
	Crude oil derivatives		—				(3		)		—				(3		)
	Coal derivatives		—				(1		)		—				(1		)
	Total liabilities from commodity risk management activities		—				(137		)		(26		)		(163		)
	Liabilities from interest rate contracts		—				(44		)		—				(44		)
	Liabilities from outstanding common stock warrants		(61		)		—				—				(61		)
	Total liabilities		$	(61	)		$	(181	)		$	(26	)		$	(268	)
Sensitivity to Changes in Significant Unobservable Inputs for Level 3 Valuations	The significant unobservable inputs used in the valuation of Dynegy’s contracts classified as Level 3 as of March 31, 2015 are as follows:
	Transaction Type		Quantity			Unit of Measure		Net Fair Value				Valuation Technique		Significant Unobservable Input		Significant Unobservable Inputs Range
	(dollars in millions)
	Electricity derivatives:
	Forward contracts—power (1)		(4	)		Million MWh		$	5			Basis spread + liquid location		Basis spread		$5.00-$7.00
	FTRs		7			Million MWh		$	(1	)		Historical congestion		Forward price		$0.00-$3.00
	__________________________________________
	-1	Represents forward financial and physical transactions at illiquid pricing locations.
Schedule of Changes in Fair Value of Financial Instruments	The following tables set forth a reconciliation of changes in the fair value of financial instruments classified as Level 3 in the fair value hierarchy:
			Three Months Ended March 31, 2015
	(amounts in millions)		Electricity				Total
			Derivatives
	Balance at December 31, 2014		$	(4	)		$	(4	)
	Total gains included in earnings		3				3
	Settlements (1)		5				5
	Balance at March 31, 2015		$	4			$	4
	Unrealized gains relating to instruments held as of March 31, 2015		$	3			$	3
			Three Months Ended March 31, 2014
	(amounts in millions)		Electricity				Heat Rate Derivatives				Total
			Derivatives
	Balance at December 31, 2013		$	11			$	(1	)		$	10
	Total losses included in earnings		(23		)		—				(23		)
	Settlements (1)		2				—				2
	Balance at March 31, 2014		$	(10	)		$	(1	)		$	(11	)
	Unrealized losses relating to instruments held as of March 31, 2014		$	(23	)		$	—			$	(23	)
	__________________________________________
	-1	For purposes of these tables, we define settlements as the beginning of period fair value of contracts that settled during the period.
Fair Value of Financial Assets and Liabilities	Unless otherwise noted, the fair value of debt as reflected in the table has been calculated based on the average of certain available broker quotes as of March 31, 2015 and December 31, 2014, respectively.
			March 31, 2015								December 31, 2014
	(amounts in millions)		Carrying				Fair				Carrying				Fair
			Amount				Value				Amount				Value
	Dynegy Inc.:
	Tranche B-2 Term Loan, due 2020 (1)(2)		$	(783	)		$	(786	)		$	(785	)		$	(775	)
	5.875% Senior Notes, due 2023 (2)		$	(500	)		$	(486	)		$	(500	)		$	(475	)
	Emissions Repurchase Agreements (2)		$	—			$	—			$	(23	)		$	(23	)
	Interest rate derivatives (2)		$	(49	)		$	(49	)		$	(44	)		$	(44	)
	Commodity-based derivative contracts (3)		$	(16	)		$	(16	)		$	(48	)		$	(48	)
	Common stock warrants (4)		$	(66	)		$	(66	)		$	(61	)		$	(61	)
	Dynegy Finance I, Inc.:
	6.75% Senior Notes, due 2019 (2)		$	(840	)		$	(874	)		$	(840	)		$	(853	)
	7.375% Senior Notes, due 2022 (2)		$	(700	)		$	(739	)		$	(700	)		$	(711	)
	7.625% Senior Notes, due 2024 (2)		$	(500	)		$	(531	)		$	(500	)		$	(509	)
	Dynegy Finance II, Inc.:
	6.75% Senior Notes, due 2019 (2)		$	(1,260	)		$	(1,310	)		$	(1,260	)		$	(1,279	)
	7.375% Senior Notes, due 2022 (2)		$	(1,050	)		$	(1,108	)		$	(1,050	)		$	(1,066	)
	7.625% Senior Notes, due 2024 (2)		$	(750	)		$	(797	)		$	(750	)		$	(763	)
	Genco:
	7.95% Senior Notes Series F, due 2032 (2)(5)		$	(224	)		$	(240	)		$	(224	)		$	(241	)
	7.00% Senior Notes Series H, due 2018 (2)(5)		$	(270	)		$	(278	)		$	(268	)		$	(264	)
	6.30% Senior Notes Series I, due 2020 (2)(5)		$	(208	)		$	(217	)		$	(206	)		$	(208	)
	__________________________________________
	-1	Carrying amount includes an unamortized discount of $3 million as of March 31, 2015 and December 31, 2014. Please read Note 8—Debt for further discussion.
	-2	The fair values of these financial instruments are classified as Level 2 within the fair value hierarchy levels.
	-3	Carrying amount of commodity-based derivative contracts excludes $2 million and $9 million of cash posted as collateral, as of March 31, 2015 and December 31, 2014, respectively.
	-4	The fair value of the common stock warrants is classified as Level 1 within the fair value hierarchy levels.
	-5	Combined carrying amounts as of March 31, 2015 and December 31, 2014 include unamortized discounts of $123 million and $127 million, respectively. Please read Note 8—Debt for further discussion.

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Changes in accumulated other comprehensive income, net of tax, by component are as follows:
			Three Months Ended March 31,
	(amounts in millions)		2015			2014
	Beginning of period		$	20		$	58
	Other comprehensive loss before reclassifications:
	Actuarial loss (net of tax of zero and zero, respectively)		—			(2		)
	Amounts reclassified from accumulated other comprehensive income:
	Amortization of unrecognized prior service cost (credit) and actuarial loss (gain) (net of tax of zero and zero, respectively) (1)		(1		)	(1		)
	Net current period other comprehensive loss, net of tax		(1		)	(3		)
	End of period		$	19		$	55
	__________________________________________
	-1	Amounts are associated with our defined benefit pension and other post-employment benefit plans and are included in the computation of net periodic pension cost (gain). Please read Note 11—Pension and Other Post-Employment Benefit Plans for further discussion.

Inventory_Tables

Inventory (Tables)	3 Months Ended
	Mar. 31, 2015
Inventory Disclosure [Abstract]
Summary of Inventories	A summary of our inventories is as follows:
	(amounts in millions)	March 31, 2015		December 31, 2014
	Materials and supplies	$	84	$	83
	Coal	134		119
	Fuel oil	3		3
	Emissions allowances	2		2
	Other	1		1
	Total	$	224	$	208

Intangible_Assets_and_Liabilit1

Intangible Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2015
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Intangible Assets and Liabilities	The following table summarizes the components of our intangible assets and liabilities as of March 31, 2015 and December 31, 2014:
			March 31, 2015									December 31, 2014
	(amounts in millions)		Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount			Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount
	Intangible Assets:
	Electricity contracts		$	111		$	(53	)	$	58		$	111		$	(46	)	$	65
	Total intangible assets		$	111		$	(53	)	$	58		$	111		$	(46	)	$	65
	Intangible Liabilities:
	Electricity contracts		$	(20	)	$	14		$	(6	)	$	(20	)	$	14		$	(6	)
	Coal contracts		(122		)	63			(59		)	(122		)	54			(68		)
	Gas transport contracts		(24		)	19			(5		)	(24		)	17			(7		)
	Total intangible liabilities		$	(166	)	$	96		$	(70	)	$	(166	)	$	85		$	(81	)
	Intangible assets and liabilities, net		$	(55	)	$	43		$	(12	)	$	(55	)	$	39		$	(16	)
	The following table presents our amortization expense (revenue) of intangible assets and liabilities for the three months ended March 31, 2015 and 2014:
			Three Months Ended March 31,
	(amounts in millions)		2015			2014
	Electricity contracts, net (1)		$	7		$	29
	Coal contracts, net (1)		(9		)	(11		)
	Gas transport contracts (2)		(2		)	(2		)
	Total		$	(4	)	$	16
	__________________________________________
	-1	The amortization of these contracts is recognized in Revenues or Cost of sales in our unaudited consolidated statements of operations.
	-2	The amortization of these contracts is recognized in Cost of sales in our unaudited consolidated statements of operations.

Debt_Tables

Debt (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	A summary of our long-term debt is as follows:
	(amounts in millions)		March 31, 2015			December 31, 2014
	Dynegy Inc.:
	Tranche B-2 Term Loan, due 2020		$	786		$	788
	5.875% Senior Notes, due 2023		500			500
	Revolving Facility		—			—
	Emissions Repurchase Agreements		—			23
	Dynegy Finance I, Inc.:
	6.75% Senior Notes, due 2019		840			840
	7.375% Senior Notes, due 2022		700			700
	7.625% Senior Notes, due 2024		500			500
	Dynegy Finance II, Inc.:
	6.75% Senior Notes, due 2019		1,260			1,260
	7.375% Senior Notes, due 2022		1,050			1,050
	7.625% Senior Notes, due 2024		750			750
	Genco:
	7.95% Senior Notes Series F, due 2032		275			275
	7.00% Senior Notes Series H, due 2018		300			300
	6.30% Senior Notes Series I, due 2020		250			250
			7,211			7,236
	Unamortized discounts on debt, net		(126		)	(130		)
			7,085			7,106
	Less: Current maturities, including unamortized discounts, net		8			31
	Total Long-term debt		$	7,077		$	7,075
Credit Agreement Compliance Ratios	The following table summarizes these required ratios:
			Required Ratio
	Restricted payment interest coverage ratio (1)		≥1.75
	Additional indebtedness interest coverage ratio (2)		≥2.50
	Additional indebtedness debt-to-capital ratio (2)		≤60%
	__________________________________________
	-1	As of the date of a restricted payment, as defined, the minimum ratio must have been achieved for the most recently ended four fiscal quarters and projected by management to be achieved for each of the subsequent four six-month periods.
	-2	Ratios must be computed on a pro forma basis considering the additional indebtedness to be incurred and the related interest expense. Other borrowings from third-party external sources are included in the definition of indebtedness and are subject to these incurrence tests.

Pension_and_Other_PostEmployme1

Pension and Other Post-Employment Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Schedule of Net Benefit Costs	The components of net periodic benefit cost (gain) were as follows:
		Pension Benefits						Other Benefits
		Three Months Ended March 31,
	(amounts in millions)	2015			2014			2015			2014
	Service cost benefits earned during period	$	3		$	3		$	—		$	—
	Interest cost on projected benefit obligation	4			4			1			1
	Expected return on plan assets	(5		)	(5		)	(1		)	(1		)
	Amortization of:
	Prior service credit	—			—			(1		)	(1		)
	Net periodic benefit cost (gain)	$	2		$	2		$	(1	)	$	(1	)

Loss_Per_Share_Tables

Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Schedule of Earnings (Loss) Per Share, Basic and Diluted	The basic and diluted loss per share from continuing operations attributable to our common stockholders during the three months ended March 31, 2015 and 2014 is shown in the following table. Please read Note 16—Capital Stock in our Form 10-K for further discussion.
			Three Months Ended March 31,
	(in millions, except per share amounts)		2015				2014
	Loss from continuing operations		$	(181	)		$	(37	)
	Less: Net income (loss) attributable to noncontrolling interest		(1		)		4
	Loss from continuing operations attributable to Dynegy Inc.		(180		)		(41		)
	Less: Dividends on preferred stock		5				—
	Loss from continuing operations attributable to Dynegy Inc. common stockholders		$	(185	)		$	(41	)
	Basic and diluted weighted-average shares (1)		124				100
	Basic and diluted loss per share from continuing operations attributable to Dynegy Inc. common stockholders (1)		$	(1.49	)		$	(0.41	)
	__________________________________________
	-1	Entities with a net loss from continuing operations are prohibited from including potential common shares in the computation of diluted per share amounts. Accordingly, we have utilized the basic shares outstanding amount to calculate both basic and diluted loss per share for the three months ended March 31, 2015 and 2014.
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following potentially dilutive securities were not included in the computation of diluted per share amounts because the effect would be anti-dilutive:
			Three Months Ended March 31,
	(in millions of shares)		2015			2014
	Stock options		1.8			1.4
	Restricted stock units		1.2			1.2
	Performance stock units		0.6			0.3
	Warrants		15.6			15.6
	Series A 5.375% mandatory convertible preferred stock		12.7			—
	Total		31.9			18.5

Condensed_Consolidating_Financ1

Condensed Consolidating Financial Information (Tables)	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Condensed Consolidating Balance Sheets	Condensed Consolidating Balance Sheet as of March 31, 2015
	(amounts in millions)
		Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	Current Assets
	Cash and cash equivalents	$	1,438		$	—		$	122		$	174		$	—		$	1,734
	Restricted cash	—			205			—			—			—			205
	Accounts receivable, net	15			—			615			163			(525		)	268
	Inventory	—			—			90			134			—			224
	Other current assets	17			7			127			75			—			226
	Total Current Assets	1,470			212			954			546			(525		)	2,657
	Property, Plant and Equipment, Net	—			—			2,781			446			—			3,227
	Other Assets
	Investment in affiliates	5,986			—			—			—			(5,986		)	—
	Other long-term assets	57			54			67			53			—			231
	Restricted cash	—			5,100			—			—			—			5,100
	Intercompany note receivable	11			—			—			—			(11		)	—
	Total Assets	$	7,524		$	5,366		$	3,802		$	1,045		$	(6,522	)	$	11,215
	Current Liabilities
	Accounts payable	$	114		$	260		$	159		$	240		$	(525	)	$	248
	Other current liabilities	71			166			155			180			—			572
	Total Current Liabilities	185			426			314			420			(525		)	820
	Long-term debt	1,275			5,100			—			702			—			7,077
	Intercompany note payable	3,042			—			—			11			(3,053		)	—
	Other long-term liabilities	186			—			109			188			—			483
	Total Liabilities	4,688			5,526			423			1,321			(3,578		)	8,380
	Stockholders’ Equity
	Dynegy Stockholders’ Equity	2,836			(160		)	6,421			(275		)	(5,986		)	2,836
	Intercompany note receivable	—			—			(3,042		)	—			3,042			—
	Total Dynegy Stockholders’ Equity	2,836			(160		)	3,379			(275		)	(2,944		)	2,836
	Noncontrolling interest	—			—			—			(1		)	—			(1		)
	Total Equity	2,836			(160		)	3,379			(276		)	(2,944		)	2,835
	Total Liabilities and Equity	$	7,524		$	5,366		$	3,802		$	1,045		$	(6,522	)	$	11,215
	Condensed Consolidating Balance Sheet as of December 31, 2014
	(amounts in millions)
		Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	Current Assets
	Cash and cash equivalents	$	1,642		$	—		$	54		$	174		$	—		$	1,870
	Restricted cash	—			113			—			—			—			113
	Accounts receivable, net	14			—			672			176			(592		)	270
	Inventory	—			—			88			120			—			208
	Other current assets	9			6			125			73			—			213
	Total Current Assets	1,665			119			939			543			(592		)	2,674
	Property, Plant and Equipment, Net	—			—			2,812			443			—			3,255
	Other Assets
	Investment in affiliates	6,133			—			—			—			(6,133		)	—
	Other long-term assets	46			47			53			57			—			203
	Restricted cash	—			5,100			—			—			—			5,100
	Intercompany note receivable	17			—			—			—			(17		)	—
	Total Assets	$	7,861		$	5,266		$	3,804		$	1,043		$	(6,742	)	$	11,232
	Current Liabilities
	Accounts payable	$	310		$	166		$	112		$	220		$	(592	)	$	216
	Other current liabilities	51			67			250			97			—			465
	Total Current Liabilities	361			233			362			317			(592		)	681
	Long-term debt	1,277			5,100			—			698			—			7,075
	Intercompany note payable	3,042			—			—			17			(3,059		)	—
	Other long-term liabilities	158			—			105			190			—			453
	Total Liabilities	4,838			5,333			467			1,222			(3,651		)	8,209
	Stockholders’ Equity
	Dynegy Stockholders’ Equity	3,023			(67		)	6,379			(179		)	(6,133		)	3,023
	Intercompany note receivable	—			—			(3,042		)	—			3,042			—
	Total Dynegy Stockholders’ Equity	3,023			(67		)	3,337			(179		)	(3,091		)	3,023
	Noncontrolling interest	—			—			—			—			—			—
	Total Equity	3,023			(67		)	3,337			(179		)	(3,091		)	3,023
	Total Liabilities and Equity	$	7,861		$	5,266		$	3,804		$	1,043		$	(6,742	)	$	11,232
Condensed Consolidating Statements of Operations	Condensed Consolidating Statements of Operations for the Three Months Ended March 31, 2015
	(amounts in millions)
		Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	Revenues	$	—		$	—		$	413		$	219		$	—		$	632
	Cost of sales, excluding depreciation expense	—			—			(239		)	(138		)	—			(377		)
	Gross margin	—			—			174			81			—			255
	Operating and maintenance expense	—			—			(60		)	(51		)	—			(111		)
	Depreciation expense	—			—			(56		)	(8		)	—			(64		)
	General and administrative expense	(1		)	—			(17		)	(12		)	—			(30		)
	Acquisition and integration costs	—			—			—			(90		)	—			(90		)
	Operating income (loss)	(1		)	—			41			(80		)	—			(40		)
	Equity in losses from investments in affiliates	(147		)	—			—			—			147			—
	Interest expense	(27		)	(93		)	—			(16		)	—			(136		)
	Other income and expense, net	(5		)	—			—			—			—			(5		)
	Income (loss) before income taxes	(180		)	(93		)	41			(96		)	147			(181		)
	Income tax expense	—			—			—			—			—			—
	Net income (loss)	(180		)	(93		)	41			(96		)	147			(181		)
	Less: Net loss attributable to noncontrolling interest	—			—			—			(1		)	—			(1		)
	Net income (loss) attributable to Dynegy Inc.	$	(180	)	$	(93	)	$	41		$	(95	)	$	147		$	(180	)
	Condensed Consolidating Statements of Operations for the Three Months Ended March 31, 2014
	(amounts in millions)
		Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	Revenues	$	—		$	558		$	204		$	—		$	762
	Cost of sales, excluding depreciation expense	—			(393		)	(159		)	—			(552		)
	Gross margin	—			165			45			—			210
	Operating and maintenance expense	—			(63		)	(47		)	—			(110		)
	Depreciation expense	—			(59		)	(8		)	—			(67		)
	General and administrative expense	(2		)	(14		)	(10		)	—			(26		)
	Acquisition and integration costs	—			—			(6		)	—			(6		)
	Operating income (loss)	(2		)	29			(26		)	—			1
	Equity in losses from investments in affiliates	(39		)	—			—			39			—
	Interest expense	(16		)	—			(14		)	—			(30		)
	Other income and expense, net	(6		)	—			—			—			(6		)
	Income (loss) before income taxes	(63		)	29			(40		)	39			(35		)
	Income tax benefit (expense)	22			—			(24		)	—			(2		)
	Net income (loss)	(41		)	29			(64		)	39			(37		)
	Less: Net income attributable to noncontrolling interest	—			—			4			—			4
	Net income (loss) attributable to Dynegy Inc.	$	(41	)	$	29		$	(68	)	$	39		$	(41	)
Condensed Consolidating Statements of Comprehensive Income (Loss)	Condensed Consolidating Statements of Comprehensive Income (Loss) for the Three Months Ended March 31, 2015
	(amounts in millions)
		Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	Net income (loss)	$	(180	)	$	(93	)	$	41		$	(96	)	$	147		$	(181	)
	Amounts reclassified from accumulated other comprehensive income:
	Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	(1		)	—			—			—			—			(1		)
	Other comprehensive loss, net of tax	(1		)	—			—			—			—			(1		)
	Comprehensive income (loss)	(181		)	(93		)	41			(96		)	147			(182		)
	Less: Comprehensive loss attributable to noncontrolling interest	—			—			—			(1		)	—			(1		)
	Total comprehensive income (loss) attributable to Dynegy Inc.	$	(181	)	$	(93	)	$	41		$	(95	)	$	147		$	(181	)
	Condensed Consolidating Statements of Comprehensive Income (Loss) for the Three Months Ended March 31, 2014
	(amounts in millions)
		Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	Net income (loss)	$	(41	)	$	29		$	(64	)	$	39		$	(37	)
	Other comprehensive income (loss) before reclassifications:
	Actuarial loss, net of tax of zero	—			—			(3		)	—			(3		)
	Amounts reclassified from accumulated other comprehensive income:
	Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	(1		)	—			—			—			(1		)
	Other comprehensive income (loss) from investment in affiliates	(3		)	—			—			3			—
	Other comprehensive income (loss), net of tax	(4		)	—			(3		)	3			(4		)
	Comprehensive income (loss)	(45		)	29			(67		)	42			(41		)
	Less: Comprehensive income (loss) attributable to noncontrolling interest	(1		)	—			3			1			3
	Total comprehensive income (loss) attributable to Dynegy Inc.	$	(44	)	$	29		$	(70	)	$	41		$	(44	)
Condensed Consolidating Statements of Cash Flow	Condensed Consolidating Statements of Cash Flow for the Three Months Ended March 31, 2015
	(amounts in millions)
		Parent			Escrow Issuers			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	CASH FLOWS FROM OPERATING ACTIVITIES:
	Net cash provided by (used in) operating activities	$	2		$	(94	)	$	46		$	(9	)	$	—		$	(55	)
	CASH FLOWS FROM INVESTING ACTIVITIES:
	Capital expenditures	—			—			(29		)	(11		)	—			(40		)
	Net intercompany transfers	(188		)	—			—			—			188			—
	Net cash provided by (used in) investing activities	(188		)	—			(29		)	(11		)	188			(40		)
	CASH FLOWS FROM FINANCING ACTIVITIES:
	Repayments of borrowings	(2		)	—			(23		)	—			—			(25		)
	Dividends paid	(7		)	—			—			—			—			(7		)
	Net intercompany transfers	—			94			74			20			(188		)	—
	Interest rate swap settlement payments	(4		)	—			—			—			—			(4		)
	Other financing	(5		)	—			—			—			—			(5		)
	Net cash provided by (used in) financing activities	(18		)	94			51			20			(188		)	(41		)
	Net increase (decrease) in cash and cash equivalents	(204		)	—			68			—			—			(136		)
	Cash and cash equivalents, beginning of period	1,642			—			54			174			—			1,870
	Cash and cash equivalents, end of period	$	1,438		$	—		$	122		$	174		$	—		$	1,734
	Condensed Consolidating Statements of Cash Flow for the Three Months Ended March 31, 2014
	(amounts in millions)
		Parent			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	CASH FLOWS FROM OPERATING ACTIVITIES:
	Net cash provided by (used in) operating activities	$	(9	)	$	140		$	35		$	—		$	166
	CASH FLOWS FROM INVESTING ACTIVITIES:
	Capital expenditures	—			(6		)	(11		)	—			(17		)
	Net intercompany transfers	113			—			—			(113		)	—
	Net cash provided by (used in) investing activities	113			(6		)	(11		)	(113		)	(17		)
	CASH FLOWS FROM FINANCING ACTIVITIES:
	Proceeds from long-term borrowings, net of financing costs	(1		)	12			—			—			11
	Repayments of borrowings	(2		)	—			—			—			(2		)
	Net intercompany transfers	—			(142		)	29			113			—
	Interest rate swap settlement payments	(4		)	—			—			—			(4		)
	Other financing	(1		)	—			—			—			(1		)
	Net cash provided by (used in) financing activities	(8		)	(130		)	29			113			4
	Net increase in cash and cash equivalents	96			4			53			—			153
	Cash and cash equivalents, beginning of period	474			154			215			—			843
	Cash and cash equivalents, end of period	$	570		$	158		$	268		$	—		$	996

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Reportable segment information, including intercompany transactions accounted for at prevailing market rates, for the three months ended March 31, 2015 and 2014 is presented below:
	Segment Data as of and for the Three Months Ended March 31, 2015
	(amounts in millions)	Coal			IPH			Gas			Other and			Total
											Eliminations
	Domestic:
	Unaffiliated revenues	$	143		$	219		$	270		$	—		$	632
	Intercompany revenues	(1		)	—			1			—			—
	Total revenues	$	142		$	219		$	271		$	—		$	632
	Depreciation expense	$	(10	)	$	(8	)	$	(45	)	$	(1	)	$	(64	)
	General and administrative expense	—			—			—			(30		)	(30		)
	Acquisition and integration costs	—			—			—			(90		)	(90		)
	Operating income (loss)	$	7		$	22		$	52		$	(121	)	$	(40	)
	Interest expense										(136		)	(136		)
	Other income and expense, net	—			—			—			(5		)	(5		)
	Loss before income taxes													(181		)
	Income tax expense										—			—
	Net loss													(181		)
	Less: Net loss attributable to noncontrolling interest													(1		)
	Net loss attributable to Dynegy Inc.													$	(180	)
	Identifiable assets (domestic)	$	1,162		$	1,037		$	2,105		$	6,911		$	11,215
	Capital expenditures	$	(3	)	$	(11	)	$	(24	)	$	(2	)	$	(40	)
	Segment Data as of and for the Three Months Ended March 31, 2014
	(amounts in millions)	Coal			IPH			Gas			Other and			Total
											Eliminations
	Domestic:
	Unaffiliated revenues	$	161		$	203		$	398		$	—		$	762
	Intercompany revenues	(5		)	1			4			—			—
	Total revenues	$	156		$	204		$	402		$	—		$	762
	Depreciation expense	$	(14	)	$	(8	)	$	(44	)	$	(1	)	$	(67	)
	General and administrative expense	—			—			—			(26		)	(26		)
	Operating income (loss)	$	9		$	(16	)	$	34		$	(26	)	$	1
	Interest expense										(30		)	(30		)
	Other income and expense, net	—			—			—			(6		)	(6		)
	Loss before income taxes													(35		)
	Income tax expense										(2		)	(2		)
	Net loss													(37		)
	Less: Net income attributable to noncontrolling interest													4
	Net loss attributable to Dynegy Inc.													$	(41	)
	Identifiable assets (domestic)	$	1,198		$	1,203		$	2,202		$	749		$	5,352
	Capital expenditures	$	(3	)	$	(11	)	$	(2	)	$	(1	)	$	(17	)

Subsequent_Events_Tables

Subsequent Events (Tables)	3 Months Ended
	Mar. 31, 2015
Subsequent Events [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table sets forth the debt assumed by Dynegy following the EquiPower Closing Date and the Duke Midwest Closing Date:
	(amounts in millions)	2-Apr-15
	Dynegy Inc.:
	6.75% Senior Notes, due 2019	$	2,100
	7.375% Senior Notes, due 2022	$	1,750
	7.625% Senior Notes, due 2024	$	1,250

Basis_of_Presentation_and_Orga1

Basis of Presentation and Organization (Details)	3 Months Ended
	Mar. 31, 2015
	segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments	3

Risk_Management_Activities_Der2

Risk Management Activities, Derivatives and Financial Instruments (Narratives) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
Minimum
Derivative [Line Items]
Rolling time period over which the entity can sell energy and capacity through near-term contractual arrangements	1 year
Maximum
Derivative [Line Items]
Rolling time period over which the entity can sell energy and capacity through near-term contractual arrangements	3 years
Commodity Contract
Derivative [Line Items]
Credit risk derivative liabilities at fair value	1
Fair value of collateral	0

Risk_Management_Activities_Der3

Risk Management Activities, Derivatives and Financial Instruments (Schedule of Derivative Contracts and Interest Rate Swaps) (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Millions, except Share data, unless otherwise specified
Derivative [Line Items]
Number of securities called by each warrant or right	1
Not Designated as Hedging Instrument
Derivative [Line Items]
Margin and collateral netting	$2		$9
Not Designated as Hedging Instrument | Interest rate swaps
Derivative [Line Items]
Number of instruments held	783,000,000
Fair value of derivatives held	-49	[1]
Commodity contracts: | Prepayments and Other Current Assets
Derivative [Line Items]
Margin and collateral netting	2		9
Electricity derivatives | Not Designated as Hedging Instrument | Future contracts
Derivative [Line Items]
Number of instruments held	-18,000,000	[2]
Fair value of derivatives held	80	[1],[2]
Electricity basis derivatives | Not Designated as Hedging Instrument | Future contracts
Derivative [Line Items]
Number of instruments held	-12,000,000	[3]
Fair value of derivatives held	-6	[1],[3]
Natural gas derivatives | Not Designated as Hedging Instrument | Future contracts
Derivative [Line Items]
Number of instruments held	85,000,000	[2]
Fair value of derivatives held	-81	[1],[2]
Natural gas basis derivatives | Not Designated as Hedging Instrument | Future contracts
Derivative [Line Items]
Number of instruments held	22,000,000
Fair value of derivatives held	-2	[1]
Diesel fuel derivatives | Not Designated as Hedging Instrument | Future contracts
Derivative [Line Items]
Number of instruments held	6,000,000
Fair value of derivatives held	-5	[1]
Coal derivatives | Not Designated as Hedging Instrument | Future contracts
Derivative [Line Items]
Number of instruments held	0
Fair value of derivatives held	-1	[1]
Crude oil derivatives | Not Designated as Hedging Instrument | Future contracts
Derivative [Line Items]
Number of instruments held	0
Fair value of derivatives held	-2	[1]
Emissions derivatives | Not Designated as Hedging Instrument | Future contracts
Derivative [Line Items]
Number of instruments held	5,000,000
Fair value of derivatives held	1	[1]
Common stock warrants | Not Designated as Hedging Instrument
Derivative [Line Items]
Number of instruments held	16,000,000	[4]
Fair value of derivatives held	($66)	[1],[4]
[1]	Includes both asset and liability risk management positions, but excludes margin and collateral netting of $2 million.
[2]	Mainly comprised of swaps, options and physical forwards.
[3]	Comprised of FTRs and swaps.
[4]	Each warrant is convertible into one share of Dynegy common stock.

Risk_Management_Activities_Der4

Risk Management Activities, Derivatives and Financial Instruments (Schedule of Derivative Instruments in the Balance Sheet) (Details) (Not Designated as Hedging Instrument, USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Risk Management Activities, Derivatives and Financial Instruments
Derivative Assets, Gross Fair Value	$118	$115
Derivative Asset, Contract Netting	-34	-35
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0	0
Derivative Assets, Net Fair Value	84	80
Derivative Liabilities, Gross Fair Value	-249	-268
Derivative Liability, Contract Netting	34	35
Margin and collateral netting	2	9
Derivative Liabilities, Net Fair Value	-213	-224
Derivative Assets (Liabilities), Gross Fair Value	-131	-153
Derivative Asset and Liability Contract Netting	0	0
Derivative Asset And Liability, Collateral, Obligation to Return Cash, Offset	2	9
Derivative Assets (Liabilities), Net Fair Value	-129	-144
Assets from Risk Management Activities | Commodity Contract
Risk Management Activities, Derivatives and Financial Instruments
Derivative Assets, Gross Fair Value	118	115
Derivative Asset, Contract Netting	-34	-35
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0	0
Derivative Assets, Net Fair Value	84	80
Liabilities from Risk Management Activities | Commodity Contract
Risk Management Activities, Derivatives and Financial Instruments
Derivative Liabilities, Gross Fair Value	-134	-163
Derivative Liability, Contract Netting	34	35
Margin and collateral netting	2	9
Derivative Liabilities, Net Fair Value	-98	-119
Liabilities from Risk Management Activities | Interest rate contracts
Risk Management Activities, Derivatives and Financial Instruments
Derivative Liabilities, Gross Fair Value	-49	-44
Derivative Liability, Contract Netting	0	0
Margin and collateral netting	0	0
Derivative Liabilities, Net Fair Value	-49	-44
Other Liabilities | Common stock warrants
Risk Management Activities, Derivatives and Financial Instruments
Derivative Liabilities, Gross Fair Value	-66	-61
Derivative Liability, Contract Netting	0	0
Margin and collateral netting	0	0
Derivative Liabilities, Net Fair Value	($66)	($61)

Risk_Management_Activities_Der5

Risk Management Activities, Derivatives and Financial Instruments (Schedule of Collateral Posted and Balance Sheet Location) (Details) (Commodity Contract, Prepayments and Other Current Assets, USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Commodity Contract | Prepayments and Other Current Assets
Derivative [Line Items]
Gross collateral posted with counterparties	$59	$49
Less: Collateral netted against risk management liabilities	2	9
Net collateral within Prepayments and other current assets	$57	$40

Risk_Management_Activities_Der6

Risk Management Activities, Derivatives and Financial Instruments (Schedule of Derivative Instruments, Gain (Loss) in the Statement of Operations) (Details) (Not Designated as Hedging Instrument, USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Commodity Contract | Revenues
Derivative Instruments, Gain (Loss) [Line Items]
Recognized gain (loss) on derivatives	$19	($173)
Interest rate contracts | Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Recognized gain (loss) on derivatives	-9	3
Common stock warrants | Other income (expense), net
Derivative Instruments, Gain (Loss) [Line Items]
Recognized gain (loss) on derivatives	($5)	($6)

Fair_Value_Measurements_Schedu

Fair Value Measurements (Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis) (Details) (Fair Value, Measurements, Recurring, USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Assets:
Total assets from commodity risk management activities	$118	$115
Liabilities:
Liabilities from commodity risk management activities:	-134	-163
Liabilities from interest rate contracts	-49	-44
Total liabilities	-249	-268
Electricity Derivatives
Assets:
Assets from commodity risk management activities:	113	110
Liabilities:
Liabilities from commodity risk management activities:	-39	-53
Natural gas derivatives
Assets:
Assets from commodity risk management activities:	4	3
Liabilities:
Liabilities from commodity risk management activities:	-87	-100
Emissions derivatives
Assets:
Assets from commodity risk management activities:	1	2
Diesel fuel derivatives
Liabilities:
Liabilities from commodity risk management activities:	-5	-6
Crude oil derivatives
Liabilities:
Liabilities from commodity risk management activities:	-2	-3
Coal derivatives
Liabilities:
Liabilities from commodity risk management activities:	-1	-1
Liabilities from outstanding common stock warrants
Liabilities:
Liabilities from outstanding common stock warrants	-66	-61
Level 1
Assets:
Total assets from commodity risk management activities	0	0
Liabilities:
Liabilities from commodity risk management activities:	0	0
Liabilities from interest rate contracts	0	0
Total liabilities	-66	-61
Level 1 | Electricity Derivatives
Assets:
Assets from commodity risk management activities:	0	0
Liabilities:
Liabilities from commodity risk management activities:	0	0
Level 1 | Natural gas derivatives
Assets:
Assets from commodity risk management activities:	0	0
Liabilities:
Liabilities from commodity risk management activities:	0	0
Level 1 | Emissions derivatives
Assets:
Assets from commodity risk management activities:	0	0
Level 1 | Diesel fuel derivatives
Liabilities:
Liabilities from commodity risk management activities:	0	0
Level 1 | Crude oil derivatives
Liabilities:
Liabilities from commodity risk management activities:	0	0
Level 1 | Coal derivatives
Liabilities:
Liabilities from commodity risk management activities:	0	0
Level 1 | Liabilities from outstanding common stock warrants
Liabilities:
Liabilities from outstanding common stock warrants	-66	-61
Level 2
Assets:
Total assets from commodity risk management activities	101	93
Liabilities:
Liabilities from commodity risk management activities:	-121	-137
Liabilities from interest rate contracts	-49	-44
Total liabilities	-170	-181
Level 2 | Electricity Derivatives
Assets:
Assets from commodity risk management activities:	96	88
Liabilities:
Liabilities from commodity risk management activities:	-26	-27
Level 2 | Natural gas derivatives
Assets:
Assets from commodity risk management activities:	4	3
Liabilities:
Liabilities from commodity risk management activities:	-87	-100
Level 2 | Emissions derivatives
Assets:
Assets from commodity risk management activities:	1	2
Level 2 | Diesel fuel derivatives
Liabilities:
Liabilities from commodity risk management activities:	-5	-6
Level 2 | Crude oil derivatives
Liabilities:
Liabilities from commodity risk management activities:	-2	-3
Level 2 | Coal derivatives
Liabilities:
Liabilities from commodity risk management activities:	-1	-1
Level 2 | Liabilities from outstanding common stock warrants
Liabilities:
Liabilities from outstanding common stock warrants	0	0
Level 3
Assets:
Total assets from commodity risk management activities	17	22
Liabilities:
Liabilities from commodity risk management activities:	-13	-26
Liabilities from interest rate contracts	0	0
Total liabilities	-13	-26
Level 3 | Electricity Derivatives
Assets:
Assets from commodity risk management activities:	17	22
Liabilities:
Liabilities from commodity risk management activities:	-13	-26
Level 3 | Natural gas derivatives
Assets:
Assets from commodity risk management activities:	0	0
Liabilities:
Liabilities from commodity risk management activities:	0	0
Level 3 | Emissions derivatives
Assets:
Assets from commodity risk management activities:	0	0
Level 3 | Diesel fuel derivatives
Liabilities:
Liabilities from commodity risk management activities:	0	0
Level 3 | Crude oil derivatives
Liabilities:
Liabilities from commodity risk management activities:	0	0
Level 3 | Coal derivatives
Liabilities:
Liabilities from commodity risk management activities:	0	0
Level 3 | Liabilities from outstanding common stock warrants
Liabilities:
Liabilities from outstanding common stock warrants	$0	$0

Fair_Value_Measurements_Sensit

Fair Value Measurements (Sensitivity to Changes in Significant Unobservable Inputs for Level 3 Valuations) (Details) (Market Approach Valuation Technique, Level 3, Fair Value, Measurements, Recurring, USD $)	3 Months Ended
	Mar. 31, 2015
Forward Contracts Power
Fair Value Inputs, Equity, Quantitative Information [Line Items]
Number of instruments held	-4,000,000	[1]
Fair value of derivatives held	$5,000,000	[1]
Forward Contracts Power | Minimum
Fair Value Inputs, Equity, Quantitative Information [Line Items]
Basis spread	5	[1]
Forward Contracts Power | Maximum
Fair Value Inputs, Equity, Quantitative Information [Line Items]
Basis spread	7	[1]
Financial Transmission Rights
Fair Value Inputs, Equity, Quantitative Information [Line Items]
Number of instruments held	7,000,000
Fair value of derivatives held	-1,000,000
Financial Transmission Rights | Minimum
Fair Value Inputs, Equity, Quantitative Information [Line Items]
Forward price	0
Financial Transmission Rights | Maximum
Fair Value Inputs, Equity, Quantitative Information [Line Items]
Forward price	$3
[1]	Represents forward financial and physical transactions at illiquid pricing locations.

Fair_Value_Measurements_Schedu1

Fair Value Measurements (Schedule of Changes in Fair Value of Financial Instruments) (Details) (Level 3, USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at December 31, 2014	($4)		$10
Total gains included in earnings	3		-23
Settlements	5	[1]	2	[1]
Balance at March 31, 2015	4		-11
Unrealized gains relating to instruments held as of March 31, 2015	3		-23
Electricity Derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at December 31, 2014	-4		11
Total gains included in earnings	3		-23
Settlements	5	[1]	2	[1]
Balance at March 31, 2015	4		-10
Unrealized gains relating to instruments held as of March 31, 2015	3		-23
Heat Rate Derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at December 31, 2014			-1
Total gains included in earnings			0
Settlements			0	[1]
Balance at March 31, 2015			-1
Unrealized gains relating to instruments held as of March 31, 2015			$0
[1]	For purposes of these tables, we define settlements as the beginning of period fair value of contracts that settled during the period.

Fair_Value_Measurements_Schedu2

Fair Value Measurements (Schedule of Financial Assets and Liabilities) (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Millions, unless otherwise specified
Not Designated as Hedging Instrument
Fair value of Financial Instruments
Margin and collateral netting	$2		$9
Commodity Contract | Prepayments and Other Current Assets
Fair value of Financial Instruments
Margin and collateral netting	2		9
5.875% Senior Notes, Due June 2023
Fair value of Financial Instruments
Stated interest rate	5.88%
7.95% Genco Senior Notes Series F due 2032
Fair value of Financial Instruments
Stated interest rate	7.95%
7.00% Genco Senior Notes Series H due 2018
Fair value of Financial Instruments
Stated interest rate	7.00%
6.30% Genco Senior Notes Series I due 2020
Fair value of Financial Instruments
Stated interest rate	6.30%
Carrying Amount | Dynegy, Inc. | Common stock warrants
Fair value of Financial Instruments
Common stock warrants	-66	[1]	-61	[1]
Carrying Amount | Dynegy, Inc. | Interest rate contracts | Not Designated as Hedging Instrument
Fair value of Financial Instruments
Interest rate derivatives	-49	[2]	-44	[2]
Carrying Amount | Dynegy, Inc. | Commodity Contract | Not Designated as Hedging Instrument
Fair value of Financial Instruments
Commodity-based derivative contracts	-16	[3]	-48	[3]
Carrying Amount | Dynegy, Inc. | Term Facilities Tranche B-2
Fair value of Financial Instruments
Long-term debt, gross	-783	[2],[4]	-785	[2],[4]
Carrying Amount | Dynegy, Inc. | Term Facilities Tranche B-2 | Secured Debt
Fair value of Financial Instruments
Unamortized loan commitment and origination fees and unamortized discounts or premiums	3		3
Carrying Amount | Dynegy, Inc. | 5.875% Senior Notes, Due June 2023
Fair value of Financial Instruments
Long-term debt, gross	-500	[2]	-500	[2]
Carrying Amount | Dynegy, Inc. | Emissions Repurchase Agreements
Fair value of Financial Instruments
Long-term debt, gross	0	[2]	-23	[2]
Carrying Amount | Dynegy Finance I, Inc | Senior Notes 6.75%, Due 2019
Fair value of Financial Instruments
Long-term debt, gross	-840	[2]	-840	[2]
Carrying Amount | Dynegy Finance I, Inc | Senior Notes 7.375%, Due 2022
Fair value of Financial Instruments
Long-term debt, gross	-700	[2]	-700	[2]
Carrying Amount | Dynegy Finance I, Inc | Senior Notes 7.625%, Due 2024
Fair value of Financial Instruments
Long-term debt, gross	-500	[2]	-500	[2]
Carrying Amount | Dynegy Finance II, Inc | Senior Notes 6.75%, Due 2019
Fair value of Financial Instruments
Long-term debt, gross	-1,260	[2]	-1,260	[2]
Carrying Amount | Dynegy Finance II, Inc | Senior Notes 7.375%, Due 2022
Fair value of Financial Instruments
Long-term debt, gross	-1,050	[2]	-1,050	[2]
Carrying Amount | Dynegy Finance II, Inc | Senior Notes 7.625%, Due 2024
Fair value of Financial Instruments
Long-term debt, gross	-750	[2]	-750	[2]
Carrying Amount | Genco | Senior Notes Series F 7.95% Due 2032
Fair value of Financial Instruments
Long-term debt, gross	-224	[2],[5]	-224	[2],[5]
Carrying Amount | Genco | Senior Notes Series F 7.95% Due 2032 | Unsecured Debt
Fair value of Financial Instruments
Unamortized loan commitment and origination fees and unamortized discounts or premiums	123		127
Carrying Amount | Genco | Senior Notes Series H 7.00% Due 2018
Fair value of Financial Instruments
Long-term debt, gross	-270	[2],[5]	-268	[2],[5]
Carrying Amount | Genco | Senior Notes Series I 6.30% Due 2020
Fair value of Financial Instruments
Long-term debt, gross	-208	[2],[5]	-206	[2],[5]
Fair Value | Dynegy, Inc. | Common stock warrants
Fair value of Financial Instruments
Common stock warrants	-66	[1]	-61	[1]
Fair Value | Dynegy, Inc. | Interest rate contracts | Not Designated as Hedging Instrument
Fair value of Financial Instruments
Interest rate derivatives	-49	[2]	-44	[2]
Fair Value | Dynegy, Inc. | Commodity Contract | Not Designated as Hedging Instrument
Fair value of Financial Instruments
Commodity-based derivative contracts	-16	[3]	-48	[3]
Fair Value | Dynegy, Inc. | Term Facilities Tranche B-2
Fair value of Financial Instruments
Long-term debt, gross	-786	[2],[4]	-775	[2],[4]
Fair Value | Dynegy, Inc. | 5.875% Senior Notes, Due June 2023
Fair value of Financial Instruments
Long-term debt, gross	-486	[2]	-475	[2]
Fair Value | Dynegy, Inc. | Emissions Repurchase Agreements
Fair value of Financial Instruments
Long-term debt, gross	0	[2]	-23	[2]
Fair Value | Dynegy Finance I, Inc | Senior Notes 6.75%, Due 2019
Fair value of Financial Instruments
Long-term debt, gross	-874	[2]	-853	[2]
Fair Value | Dynegy Finance I, Inc | Senior Notes 7.375%, Due 2022
Fair value of Financial Instruments
Long-term debt, gross	-739	[2]	-711	[2]
Fair Value | Dynegy Finance I, Inc | Senior Notes 7.625%, Due 2024
Fair value of Financial Instruments
Long-term debt, gross	-531	[2]	-509	[2]
Fair Value | Dynegy Finance II, Inc | Senior Notes 6.75%, Due 2019
Fair value of Financial Instruments
Long-term debt, gross	-1,310	[2]	-1,279	[2]
Fair Value | Dynegy Finance II, Inc | Senior Notes 7.375%, Due 2022
Fair value of Financial Instruments
Long-term debt, gross	-1,108	[2]	-1,066	[2]
Fair Value | Dynegy Finance II, Inc | Senior Notes 7.625%, Due 2024
Fair value of Financial Instruments
Long-term debt, gross	-797	[2]	-763	[2]
Fair Value | Genco | Senior Notes Series F 7.95% Due 2032
Fair value of Financial Instruments
Long-term debt, gross	-240	[2],[5]	-241	[2],[5]
Fair Value | Genco | Senior Notes Series H 7.00% Due 2018
Fair value of Financial Instruments
Long-term debt, gross	-278	[2],[5]	-264	[2],[5]
Fair Value | Genco | Senior Notes Series I 6.30% Due 2020
Fair value of Financial Instruments
Long-term debt, gross	($217)	[2],[5]	($208)	[2],[5]
Dynegy Finance I, Inc | Senior Notes 6.75%, Due 2019
Fair value of Financial Instruments
Stated interest rate	6.75%
Dynegy Finance I, Inc | Senior Notes 7.375%, Due 2022
Fair value of Financial Instruments
Stated interest rate	7.38%
Dynegy Finance I, Inc | Senior Notes 7.625%, Due 2024
Fair value of Financial Instruments
Stated interest rate	7.63%
Dynegy Finance II, Inc | Senior Notes 6.75%, Due 2019
Fair value of Financial Instruments
Stated interest rate	6.75%
Dynegy Finance II, Inc | Senior Notes 7.375%, Due 2022
Fair value of Financial Instruments
Stated interest rate	7.38%
Dynegy Finance II, Inc | Senior Notes 7.625%, Due 2024
Fair value of Financial Instruments
Stated interest rate	7.63%
[1]	The fair value of the common stock warrants is classified as Level 1 within the fair value hierarchy levels.
[2]	The fair values of these financial instruments are classified as Level 2 within the fair value hierarchy levels.
[3]	Carrying amount of commodity-based derivative contracts excludes $2 million and $9 million of cash posted as collateral, as of March 31, 2015 and December 31, 2014, respectively.
[4]	Carrying amount includes an unamortized discount of $3 million as of March 31, 2015 and December 31, 2014. Please read Note 8—Debt for further discussion.
[5]	Combined carrying amounts as of March 31, 2015 and December 31, 2014 include unamortized discounts of $123 million and $127 million, respectively. Please read Note 8—Debt for further discussion.

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Accumulated Other Comprehensive Income [Roll Forward]
Beginning of period	$20		$58
Actuarial loss (net of tax of zero and zero, respectively)	0		-2
Amortization of unrecognized prior service cost (credit) and actuarial loss (gain) (net of tax of zero and zero, respectively)	-1	[1]	-1	[1]
Net current period other comprehensive loss, net of tax	-1		-3
End of period	19		55
Tax on actuarial loss	0		0
Tax on amortization of unrecognized prior service cost (credit) and actuarial loss (gain)	$0	[1]	$0	[1]
[1]	Amounts are associated with our defined benefit pension and other post-employment benefit plans and are included in the computation of net periodic pension cost (gain). Please read Note 11—Pension and Other Post-Employment Benefit Plans for further discussion.

Inventory_Details

Inventory (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Inventory Disclosure [Abstract]
Materials and supplies	$84	$83
Coal	134	119
Fuel oil	3	3
Emissions allowances	2	2
Other	1	1
Total	$224	$208

Intangible_Assets_and_Liabilit2

Intangible Assets and Liabilities (Intangible Assets and Liabilities) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Intangible Assets and Liabilities [Line Items]
Gross Carrying Amount	$111	$111
Accumulated Amortization	-53	-46
Net Carrying Amount	58	65
Electricity Contract Liability, Gross	-20	-20
Electricity Contract Liability, Accumulated Amortization	14	14
Electricity Contract Liability, Net	-6	-6
Coal Contract Liability, Gross	-122	-122
Coal Contract Liability, Accumulated Amortization	63	54
Coal Contract Liability, Net	-59	-68
Gas Transport Contract Liability, Gross	-24	-24
Gas Transport Liability, Accumulated Amortization	19	17
Gas Transport Liability, Net	-5	-7
Intangible Liabilities, Gross	-166	-166
Intangible Liabilities, Accumulated Amortization	96	85
Intangible Liabilities, Net	-70	-81
Intangible Assets (Liabilities), Gross	-55	-55
Intangible Assets (Liabilities), Accumulated Amortization	43	39
Intangible Assets (Liabilities), Net	-12	-16
Electricity Derivatives
Intangible Assets and Liabilities [Line Items]
Gross Carrying Amount	111	111
Accumulated Amortization	-53	-46
Net Carrying Amount	$58	$65

Intangible_Assets_and_Liabilit3

Intangible Assets and Liabilities (Amortization of Intangible Assets and Liabilities) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Intangible Assets and Liabilities [Line Items]
Amortization of intangibles	($4)		$16
Electricity contracts, net
Intangible Assets and Liabilities [Line Items]
Amortization of intangibles	7	[1]	29	[1]
Coal contracts, net
Intangible Assets and Liabilities [Line Items]
Amortization of intangibles	-9	[1]	-11	[1]
Gas transport contracts
Intangible Assets and Liabilities [Line Items]
Amortization of intangibles	($2)	[2]	($2)	[2]
[1]	The amortization of these contracts is recognized in Revenues or Cost of sales in our unaudited consolidated statements of operations.
[2]	The amortization of these contracts is recognized in Cost of sales in our unaudited consolidated statements of operations.

Debt_Schedule_of_Longterm_Debt

Debt (Schedule of Long-term Debt) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Debt Instrument [Line Items]
Carrying amount	$7,211	$7,236
Unamortized discounts on debt, net	-126	-130
Total Debt	7,085	7,106
Less: Current maturities, including unamortized discounts, net	8	31
Debt, long-term portion	7,077	7,075
Emissions Repurchase Agreements
Debt Instrument [Line Items]
Carrying amount	0	23
Tranche B-2 Term Loan, Due 2020
Debt Instrument [Line Items]
Carrying amount	786	788
5.875% Senior Notes, Due June 2023
Debt Instrument [Line Items]
Carrying amount	500	500
Stated interest rate	5.88%
Revolving Credit Facility
Debt Instrument [Line Items]
Carrying amount	0	0
7.95% Genco Senior Notes Series F due 2032
Debt Instrument [Line Items]
Carrying amount	275	275
Stated interest rate	7.95%
7.00% Genco Senior Notes Series H due 2018
Debt Instrument [Line Items]
Carrying amount	300	300
Stated interest rate	7.00%
6.30% Genco Senior Notes Series I due 2020
Debt Instrument [Line Items]
Carrying amount	250	250
Stated interest rate	6.30%
Dynegy Finance I, Inc | Senior Notes 6.75%, Due 2019
Debt Instrument [Line Items]
Carrying amount	840	840
Stated interest rate	6.75%
Dynegy Finance I, Inc | Senior Notes 7.375%, Due 2022
Debt Instrument [Line Items]
Carrying amount	700	700
Stated interest rate	7.38%
Dynegy Finance I, Inc | Senior Notes 7.625%, Due 2024
Debt Instrument [Line Items]
Carrying amount	500	500
Stated interest rate	7.63%
Dynegy Finance II, Inc | Senior Notes 6.75%, Due 2019
Debt Instrument [Line Items]
Carrying amount	1,260	1,260
Stated interest rate	6.75%
Dynegy Finance II, Inc | Senior Notes 7.375%, Due 2022
Debt Instrument [Line Items]
Carrying amount	1,050	1,050
Stated interest rate	7.38%
Dynegy Finance II, Inc | Senior Notes 7.625%, Due 2024
Debt Instrument [Line Items]
Carrying amount	$750	$750
Stated interest rate	7.63%

Debt_Narratives_Details

Debt (Narratives) (Details) (USD $)

0 Months Ended

3 Months Ended

0 Months Ended

1 Months Ended

0 Months Ended

Sep. 18, 2014

Mar. 31, 2015

Apr. 23, 2013

Oct. 31, 2014

Feb. 28, 2015

Mar. 27, 2015

Oct. 27, 2014

Apr. 02, 2015

Apr. 01, 2015

Dec. 31, 2013

Dec. 02, 2013

Apr. 30, 2015

Jan. 29, 2014

Mar. 31, 2014

Agreement

Debt Instrument [Line Items]

Maximum borrowing capacity

1,275,000,000

Number of repurchase agreements

2

Genco restricted payment interest coverage ratio minimum

1.75%

[1]

Genco additional indebtedness interest coverage ratio minimum

2.50%

[2]

Genco additional indebtedness debt-to-capital ratio maximum

60.00%

[2]

Derivative, average fixed interest rate

3.19%

Derivative, lower fixed interest rate range

1.00%

Subsequent Event

Debt Instrument [Line Items]

Maximum borrowing capacity

950,000,000

5.875% Senior Notes, Due June 2023

Debt Instrument [Line Items]

Amount of unsecured senior notes

500,000,000

Stated interest rate

5.88%

Genco Senior Notes Series F, H, and I

Debt Instrument [Line Items]

Amount of unsecured senior notes

825,000,000

Letter of Credit

Debt Instrument [Line Items]

Credit facility tenor

1 year

Credit facility optional extension period

1 year

Letter of Credit | Macquarie Bank

Debt Instrument [Line Items]

Maximum borrowing capacity

55,000,000

Letters of Credit Outstanding, Amount

55,000,000

Term Facilities Tranche B-2

Debt Instrument [Line Items]

Maximum borrowing capacity

800,000,000

Debt instrument term

7 years

Derivative, Notional amount

783,000,000

Illinois Power Marketing

Debt Instrument [Line Items]

Line of credit facility, fair value amount outstanding

0

Illinois Power Marketing | Letter of Credit and Reimbursement Agreement

Debt Instrument [Line Items]

Maximum borrowing capacity

25,000,000

Savings deposits

10,500,000

Letters of Credit Outstanding, Amount

10,000,000

CCA Repurchase Agreement

Debt Instrument [Line Items]

Assets repurchased under agreement to repurchase

6,000,000

Assets sold under agreements to repurchase, carrying amount

6,000,000

RGGI Repurchase Agreement

Debt Instrument [Line Items]

Assets repurchased under agreement to repurchase

23,000,000

Assets sold under agreements to repurchase, carrying amount

11,000,000

12,000,000

Minimum

Debt Instrument [Line Items]

Projected interest coverage ratio determination period

1 year

Maximum

Debt Instrument [Line Items]

Projected interest coverage ratio determination period

2 years

Revolving Credit Facility | Line of Credit

Debt Instrument [Line Items]

Maximum borrowing capacity

475,000,000

Debt instrument term

5 years

Line of credit facility, amount outstanding

0

Revolving Credit Facility | Letter of Credit

Debt Instrument [Line Items]

Letters of Credit Outstanding, Amount

128,000,000

Revolving Credit Facility | Illinois Power Marketing

Debt Instrument [Line Items]

Maximum borrowing capacity

25,000,000

Credit facility tenor

2 years

Credit facility optional extension period

1 year

Unsecured Debt | Senior Notes

Debt Instrument [Line Items]

Proceeds from issuance of debt

5,100,000,000

Weighted average interest rate

7.18%

Unsecured Debt | Dynegy Finance II, Inc | Senior Notes

Debt Instrument [Line Items]

Proceeds from issuance of debt

3,060,000,000

Unsecured Debt | Dynegy Finance I, Inc | Senior Notes

Debt Instrument [Line Items]

Proceeds from issuance of debt

2,040,000,000

Duke Midwest Purchase Agreement | Subsequent Event

Debt Instrument [Line Items]

Debt instrument term

5 years

Amount of unsecured senior notes

500,000,000

Duke Midwest Purchase Agreement | Revolving Credit Facility | Subsequent Event

Debt Instrument [Line Items]

Maximum borrowing capacity

600,000,000

EquiPower Acquisition | Subsequent Event

Debt Instrument [Line Items]

Debt instrument term

5 years

EquiPower Acquisition | Revolving Credit Facility | Subsequent Event

Debt Instrument [Line Items]

Maximum borrowing capacity

350,000,000

LIBOR | Illinois Power Marketing

Debt Instrument [Line Items]

Basis spread on variable rate

0.50%

LIBOR | Duke Midwest Purchase Agreement | Subsequent Event

Debt Instrument [Line Items]

Basis spread on variable rate

2.75%

LIBOR | EquiPower Acquisition | Subsequent Event

Debt Instrument [Line Items]

Basis spread on variable rate

2.75%

[1]

As of the date of a restricted payment, as defined, the minimum ratio must have been achieved for the most recently ended four fiscal quarters and projected by management to be achieved for each of the subsequent four six-month periods.

[2]

Ratios must be computed on a pro forma basis considering the additional indebtedness to be incurred and the related interest expense. Other borrowings from third-party external sources are included in the definition of indebtedness and are subject to these incurrence tests.

Commitments_and_Contingencies_

Commitments and Contingencies (Legal Proceedings) (Details) (USD $)	12 Months Ended	1 Months Ended	3 Months Ended	0 Months Ended	1 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2010	Jun. 30, 2007	Mar. 31, 2015	Dec. 16, 2014	Sep. 30, 2010
Pending Litigation
Loss Contingencies [Line Items]
Amount paid by plaintiff to defendant in dispute	$17
Illinova Generating Company Arbitration | Pending Litigation
Loss Contingencies [Line Items]
Payments for legal settlements		17
Illinova Generating Company | Illinova Generating Company Arbitration | Pending Litigation
Loss Contingencies [Line Items]
Amount paid by plaintiff to defendant in dispute			17
Illinova Generating Company | Illinova Generating Company Arbitration | Judicial Ruling
Loss Contingencies [Line Items]
Value of damages awarded			$2.50	$2.50	$17

Commitments_and_Contingencies_1

Commitments and Contingencies (Other Commitments and Contingencies) (Details) (USD $)	3 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended	1 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Jul. 31, 2013	Jun. 30, 2013	Dec. 31, 2014	Apr. 24, 2012	Dec. 31, 2013	Mar. 31, 2014	Apr. 30, 2012
	surface_impoundment				localized_area			surface_impoundment
Loss Contingencies [Line Items]
Number of CCR surface impoundments	2
Estimated minimum number of years CSA commitments will be in effect	15 years
Dynegy's CSA Commitment
Loss Contingencies [Line Items]
Minimum purchase obligation limited to any termination payments	159
Counterparty's CSA Commitment
Loss Contingencies [Line Items]
Minimum purchase obligation limited to any termination payments	214
Hennepin, East Dam
Loss Contingencies [Line Items]
Post-closure monitoring costs		5
Increase in ARO			2	3
Baldwin Groundwater, Environmental Protection Agency Regulations Compliance, Coal Combustion Residues
Loss Contingencies [Line Items]
Number of localized areas where groundwater standards were exceeded					2
Number of months to complete geotechnical/hydraulic/hydrogeologic study at Baldwin						12 months
Vermillion Facility, Old East and North Sites
Loss Contingencies [Line Items]
Estimated cost for recommended closure alternative for impoundments	3						10
Number of localized areas where groundwater standards were exceeded								2
Vermillion Facility, All Sites
Loss Contingencies [Line Items]
Estimated cost for recommended closure alternative for impoundments								2

Commitments_and_Contingencies_2

Commitments and Contingencies (Indemnifications and Guarantees) (Details) (USD $)	3 Months Ended	9 Months Ended	0 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Sep. 30, 2013	Dec. 02, 2013	Aug. 21, 2014
	Charter_Party_Agreement	Charter_Party_Agreement
Loss Contingencies [Line Items]
Number of charter agreement extensions available	1
Extension option term	1 year
VLGC Guarantee
Loss Contingencies [Line Items]
Number of charter party agreements	2
Number of charter agreements extended		1
Base commitments for charter party agreement in 2015	11
Base commitments for charter party agreement in 2016	11
LS Power Indemnities
Loss Contingencies [Line Items]
Number of claims and amount of accrued indemnifications, if any	0
LS Power Indemnities | Duke Midwest Purchase Agreement
Loss Contingencies [Line Items]
Number of claims and amount of accrued indemnifications, if any	0
Guarantee | Duke Midwest Purchase Agreement
Loss Contingencies [Line Items]
Contingent consideration arrangements, range of outcomes, high value				2,800
IPH | Limited Guaranty
Loss Contingencies [Line Items]
Number of years Ameren is required to guarantee termination fee			2 years
Contingent consideration arrangements, range of outcomes, high value			25
Maximum | Guarantee | EquiPower Acquisition
Loss Contingencies [Line Items]
Contingent consideration arrangements, range of outcomes, high value				276
Coal Commitments
Loss Contingencies [Line Items]
Purchase obligation	145
Number of new purchase contracts	3
Coal Transportation
Loss Contingencies [Line Items]
Purchase obligation	254
Number of new purchase contracts	2
Covenants, Representations and Warranties | ECP Purchasers | Guarantee | EquiPower Acquisition
Loss Contingencies [Line Items]
Indemnification obligation term	1 year
Covenants, Representations and Warranties | ECP Purchasers | Guarantee | Duke Midwest Purchase Agreement
Loss Contingencies [Line Items]
Indemnification obligation term	1 year
Fundamental Representations | Guarantee | EquiPower Acquisition
Loss Contingencies [Line Items]
Indemnification obligation term	2 years
Fundamental Representations | Guarantee | Duke Midwest Purchase Agreement
Loss Contingencies [Line Items]
Indemnification obligation term	3 years
Tax Matters, Additional Guarantee Beyond Statute of Limitations | Guarantee | Duke Midwest Purchase Agreement
Loss Contingencies [Line Items]
Indemnification obligation term	30 days

Pension_and_Other_PostEmployme2

Pension and Other Post-Employment Benefit Plans (Schedule of Net Benefit Costs) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost benefits earned during period	$3	$3
Interest cost on projected benefit obligation	4	4
Expected return on plan assets	-5	-5
Amortization of: Prior service credit	0	0
Net periodic benefit cost (gain)	2	2
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost benefits earned during period	0	0
Interest cost on projected benefit obligation	1	1
Expected return on plan assets	-1	-1
Amortization of: Prior service credit	-1	-1
Net periodic benefit cost (gain)	($1)	($1)

Loss_Per_Share_Details

Loss Per Share (Details) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Earnings Per Share [Abstract]
Loss from continuing operations	($181)		($37)
Less: Net income (loss) attributable to noncontrolling interest	-1		4
Loss from continuing operations attributable to Dynegy Inc.	-180		-41
Less: Dividends on preferred stock	5		0
Loss from continuing operations attributable to Dynegy Inc. common stockholders	($185)		($41)
Basic and diluted weighted-average shares	124	[1]	100
Basic and diluted loss per share from continuing operations attributable to Dynegy Inc. common stockholders (1)	($1.49)	[1]	($0.41)	[1]
[1]	Entities with a net loss from continuing operations are prohibited from including potential common shares in the computation of diluted per share amounts. Accordingly, we have utilized the basic shares outstanding amount to calculate both basic and diluted loss per share for the three months ended March 31, 2015 and 2014.

Loss_Per_Share_AntiDilutive_Sh

Loss Per Share (Anti-Dilutive Shares - Potentially Dilutive in the Future) (Details)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	31.9	18.5
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	1.8	1.4
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	1.2	1.2
Performance stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	0.6	0.3
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	15.6	15.6
Series A 5.375% mandatory convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	12.7	0
Preferred stock dividend rate	5.38%

Condensed_Consolidating_Balanc

(Condensed Consolidating Balance Sheets) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Current Assets
Cash and cash equivalents	$1,734	$1,870	$996	$843
Restricted cash	205	113
Accounts receivable, net	268	270
Inventory	224	208
Other current assets	226	213
Total Current Assets	2,657	2,674
Property, Plant and Equipment, Net	3,227	3,255
Other Assets
Investment in affiliates	0	0
Other long-term assets	231	203
Restricted cash	5,100	5,100
Intercompany note receivable	0	0
Total Assets	11,215	11,232
Current Liabilities
Accounts payable	248	216
Other current liabilities	572	465
Total Current Liabilities	820	681
Long-term debt	7,077	7,075
Intercompany note payable	0	0
Other long-term liabilities	483	453
Total Liabilities	8,380	8,209
Stockholders’ Equity
Dynegy Stockholders’ Equity	2,836	3,023
Intercompany note receivable	0	0
Total Dynegy Stockholders’ Equity	2,836	3,023
Noncontrolling interest	-1	0
Total Equity	2,835	3,023
Total Liabilities and Equity	11,215	11,232
Parent
Current Assets
Cash and cash equivalents	1,438	1,642	570	474
Restricted cash	0	0
Accounts receivable, net	15	14
Inventory	0	0
Other current assets	17	9
Total Current Assets	1,470	1,665
Property, Plant and Equipment, Net	0	0
Other Assets
Investment in affiliates	5,986	6,133
Other long-term assets	57	46
Restricted cash	0	0
Intercompany note receivable	11	17
Total Assets	7,524	7,861
Current Liabilities
Accounts payable	114	310
Other current liabilities	71	51
Total Current Liabilities	185	361
Long-term debt	1,275	1,277
Intercompany note payable	3,042	3,042
Other long-term liabilities	186	158
Total Liabilities	4,688	4,838
Stockholders’ Equity
Dynegy Stockholders’ Equity	2,836	3,023
Intercompany note receivable	0	0
Total Dynegy Stockholders’ Equity	2,836	3,023
Noncontrolling interest	0	0
Total Equity	2,836	3,023
Total Liabilities and Equity	7,524	7,861
Escrow Issuers
Current Assets
Cash and cash equivalents	0	0
Restricted cash	205	113
Accounts receivable, net	0	0
Inventory	0	0
Other current assets	7	6
Total Current Assets	212	119
Property, Plant and Equipment, Net	0	0
Other Assets
Investment in affiliates	0	0
Other long-term assets	54	47
Restricted cash	5,100	5,100
Intercompany note receivable	0	0
Total Assets	5,366	5,266
Current Liabilities
Accounts payable	260	166
Other current liabilities	166	67
Total Current Liabilities	426	233
Long-term debt	5,100	5,100
Intercompany note payable	0	0
Other long-term liabilities	0	0
Total Liabilities	5,526	5,333
Stockholders’ Equity
Dynegy Stockholders’ Equity	-160	-67
Intercompany note receivable	0	0
Total Dynegy Stockholders’ Equity	-160	-67
Noncontrolling interest	0	0
Total Equity	-160	-67
Total Liabilities and Equity	5,366	5,266
Guarantor Subsidiaries
Current Assets
Cash and cash equivalents	122	54	158	154
Restricted cash	0	0
Accounts receivable, net	615	672
Inventory	90	88
Other current assets	127	125
Total Current Assets	954	939
Property, Plant and Equipment, Net	2,781	2,812
Other Assets
Investment in affiliates	0	0
Other long-term assets	67	53
Restricted cash	0	0
Intercompany note receivable	0	0
Total Assets	3,802	3,804
Current Liabilities
Accounts payable	159	112
Other current liabilities	155	250
Total Current Liabilities	314	362
Long-term debt	0	0
Intercompany note payable	0	0
Other long-term liabilities	109	105
Total Liabilities	423	467
Stockholders’ Equity
Dynegy Stockholders’ Equity	6,421	6,379
Intercompany note receivable	-3,042	-3,042
Total Dynegy Stockholders’ Equity	3,379	3,337
Noncontrolling interest	0	0
Total Equity	3,379	3,337
Total Liabilities and Equity	3,802	3,804
Non-Guarantor Subsidiaries
Current Assets
Cash and cash equivalents	174	174	268	215
Restricted cash	0	0
Accounts receivable, net	163	176
Inventory	134	120
Other current assets	75	73
Total Current Assets	546	543
Property, Plant and Equipment, Net	446	443
Other Assets
Investment in affiliates	0	0
Other long-term assets	53	57
Restricted cash	0	0
Intercompany note receivable	0	0
Total Assets	1,045	1,043
Current Liabilities
Accounts payable	240	220
Other current liabilities	180	97
Total Current Liabilities	420	317
Long-term debt	702	698
Intercompany note payable	11	17
Other long-term liabilities	188	190
Total Liabilities	1,321	1,222
Stockholders’ Equity
Dynegy Stockholders’ Equity	-275	-179
Intercompany note receivable	0	0
Total Dynegy Stockholders’ Equity	-275	-179
Noncontrolling interest	-1	0
Total Equity	-276	-179
Total Liabilities and Equity	1,045	1,043
Eliminations
Current Assets
Cash and cash equivalents	0	0	0	0
Restricted cash	0	0
Accounts receivable, net	-525	-592
Inventory	0	0
Other current assets	0	0
Total Current Assets	-525	-592
Property, Plant and Equipment, Net	0	0
Other Assets
Investment in affiliates	-5,986	-6,133
Other long-term assets	0	0
Restricted cash	0	0
Intercompany note receivable	-11	-17
Total Assets	-6,522	-6,742
Current Liabilities
Accounts payable	-525	-592
Other current liabilities	0	0
Total Current Liabilities	-525	-592
Long-term debt	0	0
Intercompany note payable	-3,053	-3,059
Other long-term liabilities	0	0
Total Liabilities	-3,578	-3,651
Stockholders’ Equity
Dynegy Stockholders’ Equity	-5,986	-6,133
Intercompany note receivable	3,042	3,042
Total Dynegy Stockholders’ Equity	-2,944	-3,091
Noncontrolling interest	0	0
Total Equity	-2,944	-3,091
Total Liabilities and Equity	($6,522)	($6,742)

Condensed_Consolidating_Statem

(Condensed Consolidating Statements of Operations) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Revenues	$632	$762
Cost of sales, excluding depreciation expense	-377	-552
Gross margin	255	210
Operating and maintenance expense	-111	-110
Depreciation expense	-64	-67
General and administrative expense	-30	-26
Acquisition and integration costs	-90	-6
Operating income (loss)	-40	1
Equity in losses from investments in affiliates	0	0
Interest expense	-136	-30
Other income and expense, net	-5	-6
Loss before income taxes	-181	-35
Income tax expense	0	-2
Net loss	-181	-37
Less: Net income (loss) attributable to noncontrolling interest	-1	4
Net loss attributable to Dynegy Inc.	-180	-41
Parent
Condensed Financial Statements, Captions [Line Items]
Revenues	0	0
Cost of sales, excluding depreciation expense	0	0
Gross margin	0	0
Operating and maintenance expense	0	0
Depreciation expense	0	0
General and administrative expense	-1	-2
Acquisition and integration costs	0	0
Operating income (loss)	-1	-2
Equity in losses from investments in affiliates	-147	-39
Interest expense	-27	-16
Other income and expense, net	-5	-6
Loss before income taxes	-180	-63
Income tax expense	0	22
Net loss	-180	-41
Less: Net income (loss) attributable to noncontrolling interest	0	0
Net loss attributable to Dynegy Inc.	-180	-41
Escrow Issuers
Condensed Financial Statements, Captions [Line Items]
Revenues	0
Cost of sales, excluding depreciation expense	0
Gross margin	0
Operating and maintenance expense	0
Depreciation expense	0
General and administrative expense	0
Acquisition and integration costs	0
Operating income (loss)	0
Equity in losses from investments in affiliates	0
Interest expense	-93
Other income and expense, net	0
Loss before income taxes	-93
Income tax expense	0
Net loss	-93
Less: Net income (loss) attributable to noncontrolling interest	0
Net loss attributable to Dynegy Inc.	-93
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Revenues	413	558
Cost of sales, excluding depreciation expense	-239	-393
Gross margin	174	165
Operating and maintenance expense	-60	-63
Depreciation expense	-56	-59
General and administrative expense	-17	-14
Acquisition and integration costs	0	0
Operating income (loss)	41	29
Equity in losses from investments in affiliates	0	0
Interest expense	0	0
Other income and expense, net	0	0
Loss before income taxes	41	29
Income tax expense	0	0
Net loss	41	29
Less: Net income (loss) attributable to noncontrolling interest	0	0
Net loss attributable to Dynegy Inc.	41	29
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Revenues	219	204
Cost of sales, excluding depreciation expense	-138	-159
Gross margin	81	45
Operating and maintenance expense	-51	-47
Depreciation expense	-8	-8
General and administrative expense	-12	-10
Acquisition and integration costs	-90	-6
Operating income (loss)	-80	-26
Equity in losses from investments in affiliates	0	0
Interest expense	-16	-14
Other income and expense, net	0	0
Loss before income taxes	-96	-40
Income tax expense	0	-24
Net loss	-96	-64
Less: Net income (loss) attributable to noncontrolling interest	-1	4
Net loss attributable to Dynegy Inc.	-95	-68
Eliminations
Condensed Financial Statements, Captions [Line Items]
Revenues	0	0
Cost of sales, excluding depreciation expense	0	0
Gross margin	0	0
Operating and maintenance expense	0	0
Depreciation expense	0	0
General and administrative expense	0	0
Acquisition and integration costs	0	0
Operating income (loss)	0	0
Equity in losses from investments in affiliates	147	39
Interest expense	0	0
Other income and expense, net	0	0
Loss before income taxes	147	39
Income tax expense	0	0
Net loss	147	39
Less: Net income (loss) attributable to noncontrolling interest	0	0
Net loss attributable to Dynegy Inc.	$147	$39

Condensed_Consolidating_Statem1

(Condensed Consolidating Statements of Comprehensive Income (Loss)) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	($181)	($37)
Other comprehensive income (loss) before reclassifications:
Actuarial loss, net of tax of zero	0	-3
Amounts reclassified from accumulated other comprehensive income:
Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	-1	-1
Other comprehensive income (loss) from investment in affiliates		0
Other comprehensive loss, net of tax	-1	-4
Comprehensive loss	-182	-41
Less: Comprehensive income (loss) attributable to noncontrolling interest	-1	3
Total comprehensive loss attributable to Dynegy Inc.	-181	-44
Parent
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	-180	-41
Other comprehensive income (loss) before reclassifications:
Actuarial loss, net of tax of zero		0
Amounts reclassified from accumulated other comprehensive income:
Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	-1	-1
Other comprehensive income (loss) from investment in affiliates		-3
Other comprehensive loss, net of tax	-1	-4
Comprehensive loss	-181	-45
Less: Comprehensive income (loss) attributable to noncontrolling interest	0	-1
Total comprehensive loss attributable to Dynegy Inc.	-181	-44
Escrow Issuers
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	-93
Amounts reclassified from accumulated other comprehensive income:
Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	0
Other comprehensive loss, net of tax	0
Comprehensive loss	-93
Less: Comprehensive income (loss) attributable to noncontrolling interest	0
Total comprehensive loss attributable to Dynegy Inc.	-93
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	41	29
Other comprehensive income (loss) before reclassifications:
Actuarial loss, net of tax of zero		0
Amounts reclassified from accumulated other comprehensive income:
Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	0	0
Other comprehensive income (loss) from investment in affiliates		0
Other comprehensive loss, net of tax	0	0
Comprehensive loss	41	29
Less: Comprehensive income (loss) attributable to noncontrolling interest	0	0
Total comprehensive loss attributable to Dynegy Inc.	41	29
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	-96	-64
Other comprehensive income (loss) before reclassifications:
Actuarial loss, net of tax of zero		-3
Amounts reclassified from accumulated other comprehensive income:
Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	0	0
Other comprehensive income (loss) from investment in affiliates		0
Other comprehensive loss, net of tax	0	-3
Comprehensive loss	-96	-67
Less: Comprehensive income (loss) attributable to noncontrolling interest	-1	3
Total comprehensive loss attributable to Dynegy Inc.	-95	-70
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	147	39
Other comprehensive income (loss) before reclassifications:
Actuarial loss, net of tax of zero		0
Amounts reclassified from accumulated other comprehensive income:
Amortization of unrecognized prior service credit and actuarial gain, net of tax of zero	0	0
Other comprehensive income (loss) from investment in affiliates		3
Other comprehensive loss, net of tax	0	3
Comprehensive loss	147	42
Less: Comprehensive income (loss) attributable to noncontrolling interest	0	1
Total comprehensive loss attributable to Dynegy Inc.	$147	$41

Condensed_Consolidating_Statem2

(Condensed Consolidating Statements of Cash Flow) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	($55)	$166
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	-40	-17
Net intercompany transfers	0	0
Net cash used in investing activities	-40	-17
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from long-term borrowings, net of financing costs	0	11
Repayments of borrowings	-25	-2
Dividends paid	-7	0
Net intercompany transfers	0	0
Interest rate swap settlement payments	-4	-4
Other financing	-5	-1
Net cash provided by (used) in financing activities	-41	4
Net increase (decrease) in cash and cash equivalents	-136	153
Cash and cash equivalents, beginning of period	1,870	843
Cash and cash equivalents, end of period	1,734	996
Parent
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	2	-9
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	0	0
Net intercompany transfers	-188	113
Net cash used in investing activities	-188	113
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from long-term borrowings, net of financing costs		-1
Repayments of borrowings	-2	-2
Dividends paid	-7
Net intercompany transfers	0	0
Interest rate swap settlement payments	-4	-4
Other financing	-5	-1
Net cash provided by (used) in financing activities	-18	-8
Net increase (decrease) in cash and cash equivalents	-204	96
Cash and cash equivalents, beginning of period	1,642	474
Cash and cash equivalents, end of period	1,438	570
Escrow Issuers
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	-94
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	0
Net intercompany transfers	0
Net cash used in investing activities	0
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of borrowings	0
Dividends paid	0
Net intercompany transfers	94
Interest rate swap settlement payments	0
Other financing	0
Net cash provided by (used) in financing activities	94
Net increase (decrease) in cash and cash equivalents	0
Cash and cash equivalents, beginning of period	0
Cash and cash equivalents, end of period	0
Guarantor Subsidiaries
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	46	140
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	-29	-6
Net intercompany transfers	0	0
Net cash used in investing activities	-29	-6
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from long-term borrowings, net of financing costs		12
Repayments of borrowings	-23	0
Dividends paid	0
Net intercompany transfers	74	-142
Interest rate swap settlement payments	0	0
Other financing	0	0
Net cash provided by (used) in financing activities	51	-130
Net increase (decrease) in cash and cash equivalents	68	4
Cash and cash equivalents, beginning of period	54	154
Cash and cash equivalents, end of period	122	158
Non-Guarantor Subsidiaries
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	-9	35
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	-11	-11
Net intercompany transfers	0	0
Net cash used in investing activities	-11	-11
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from long-term borrowings, net of financing costs		0
Repayments of borrowings	0	0
Dividends paid	0
Net intercompany transfers	20	29
Interest rate swap settlement payments	0	0
Other financing	0	0
Net cash provided by (used) in financing activities	20	29
Net increase (decrease) in cash and cash equivalents	0	53
Cash and cash equivalents, beginning of period	174	215
Cash and cash equivalents, end of period	174	268
Eliminations
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	0	0
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	0	0
Net intercompany transfers	188	-113
Net cash used in investing activities	188	-113
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from long-term borrowings, net of financing costs		0
Repayments of borrowings	0	0
Dividends paid	0
Net intercompany transfers	-188	113
Interest rate swap settlement payments	0	0
Other financing	0	0
Net cash provided by (used) in financing activities	-188	113
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	$0	$0

Segment_Information_Narrative_

Segment Information (Narrative) (Details)	3 Months Ended
	Mar. 31, 2015
	segment
Segment Reporting [Abstract]
Number of reportable segments	3

Segment_Information_Segment_Re

Segment Information (Segment Reporting) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Segment Information
Revenues	$632	$762
Depreciation expense	-64	-67
General and administrative expense	-30	-26
Acquisition and integration costs	-90	-6
Operating income (loss)	-40	1
Interest expense	-136	-30
Other items, net	-5	-6
Loss before income taxes	-181	-35
Income tax expense	0	-2
Net loss	-181	-37
Less: Net income attributable to noncontrolling interest	-1	4
Net loss attributable to Dynegy Inc.	-180	-41
Identifiable assets (domestic)	11,215		11,232
Capital expenditures	-40	-17
UNITED STATES
Segment Information
Identifiable assets (domestic)	11,215	5,352
Coal
Segment Information
Revenues	142	156
Depreciation expense	-10	-14
General and administrative expense	0	0
Acquisition and integration costs	0
Operating income (loss)	7	9
Other items, net	0	0
Capital expenditures	-3	-3
Coal | UNITED STATES
Segment Information
Identifiable assets (domestic)	1,162	1,198
IPH
Segment Information
Revenues	219	204
Depreciation expense	-8	-8
General and administrative expense	0	0
Acquisition and integration costs	0
Operating income (loss)	22	-16
Other items, net	0	0
Capital expenditures	-11	-11
IPH | UNITED STATES
Segment Information
Identifiable assets (domestic)	1,037	1,203
Gas
Segment Information
Revenues	271	402
Depreciation expense	-45	-44
General and administrative expense	0	0
Acquisition and integration costs	0
Operating income (loss)	52	34
Other items, net	0	0
Capital expenditures	-24	-2
Gas | UNITED STATES
Segment Information
Identifiable assets (domestic)	2,105	2,202
Other and Eliminations
Segment Information
Revenues	0	0
Depreciation expense	-1	-1
General and administrative expense	-30	-26
Acquisition and integration costs	-90
Operating income (loss)	-121	-26
Interest expense	-136	-30
Other items, net	-5	-6
Income tax expense	0	-2
Capital expenditures	-2	-1
Other and Eliminations | UNITED STATES
Segment Information
Identifiable assets (domestic)	6,911	749
Unaffiliated revenues | UNITED STATES
Segment Information
Revenues	632	762
Unaffiliated revenues | Coal | UNITED STATES
Segment Information
Revenues	143	161
Unaffiliated revenues | IPH | UNITED STATES
Segment Information
Revenues	219	203
Unaffiliated revenues | Gas | UNITED STATES
Segment Information
Revenues	270	398
Unaffiliated revenues | Other and Eliminations | UNITED STATES
Segment Information
Revenues	0	0
Intercompany revenues | UNITED STATES
Segment Information
Revenues	0	0
Intercompany revenues | Coal | UNITED STATES
Segment Information
Revenues	-1	-5
Intercompany revenues | IPH | UNITED STATES
Segment Information
Revenues	0	1
Intercompany revenues | Gas | UNITED STATES
Segment Information
Revenues	1	4
Intercompany revenues | Other and Eliminations | UNITED STATES
Segment Information
Revenues	$0	$0

Subsequent_Events_Details

Subsequent Events (Details) (USD $)	0 Months Ended		3 Months Ended	12 Months Ended	0 Months Ended
	Mar. 03, 2015	Oct. 27, 2014	Mar. 31, 2015	Dec. 31, 2014	Apr. 01, 2015	Apr. 02, 2015	Aug. 21, 2014	Apr. 30, 2015
Subsequent Event [Line Items]
Credit agreement, maximum borrowing capacity			1,275,000,000
Long-term debt			7,085,000,000	7,106,000,000
Preferred stock dividends declared, per share amount	$1.34
Preferred stock dividends declared, amount	5,000,000
5.875% Senior Notes, Due June 2023
Subsequent Event [Line Items]
Stated interest rate			5.88%
Amount of unsecured senior notes			500,000,000
Unsecured Debt | Senior Notes
Subsequent Event [Line Items]
Proceeds from issuance of debt		5,100,000,000
Weighted average interest rate		7.18%
Series A 5.375% mandatory convertible preferred stock
Subsequent Event [Line Items]
Preferred stock, series A 5.375%			5.38%	5.38%
Dynegy Finance II, Inc | Unsecured Debt | Senior Notes
Subsequent Event [Line Items]
Proceeds from issuance of debt		3,060,000,000
Dynegy Finance I, Inc | Unsecured Debt | Senior Notes
Subsequent Event [Line Items]
Proceeds from issuance of debt		2,040,000,000
Duke Midwest Purchase Agreement | Guarantee
Subsequent Event [Line Items]
Contingent consideration arrangements, range of outcomes, high value							2,800,000,000
Brayton Purchase Agreement
Subsequent Event [Line Items]
Coal-Fired power facilities							1
EquiPower Acquisition | Guarantee | Maximum
Subsequent Event [Line Items]
Contingent consideration arrangements, range of outcomes, high value							276,000,000
Subsequent Event
Subsequent Event [Line Items]
Credit agreement, maximum borrowing capacity								950,000,000
Subsequent Event | Senior Notes 6.75%, Due 2019
Subsequent Event [Line Items]
Stated interest rate					6.75%	6.75%
Subsequent Event | Senior Notes 7.375%, Due 2022
Subsequent Event [Line Items]
Stated interest rate					7.38%	7.38%
Subsequent Event | Senior Notes 7.625%, Due 2024
Subsequent Event [Line Items]
Stated interest rate					7.63%	7.63%
Subsequent Event | Brayton Point Holdings, LLC
Subsequent Event [Line Items]
Percent of voting interests acquired					100.00%
Subsequent Event | ERC Purchase Agreement
Subsequent Event [Line Items]
Percent of voting interests acquired					100.00%
Combined cycle gas facilities acquired					5
Natural gas power facilities acquired					1
Gas and oil power facilities acquired					2
Coal-Fired power facilities					1
Subsequent Event | EquiPower Resources Corp. and Brayton Point Holdings, LLC
Subsequent Event [Line Items]
Purchase price, cash					3,350,000,000
Equity interests issued and issuable					100,000,000
Subsequent Event | ECP Purchase Agreements
Subsequent Event [Line Items]
Number of power facilities acquired					6,300
Indemnification range of outcomes high value					276,000,000
Indemnification amounts held in escrow					104,000,000
Indemnification escrow requirement period					1 year
Amount of unsecured senior notes					500,000,000
Subsequent Event | Duke Midwest Purchase Agreement
Subsequent Event [Line Items]
Percent of voting interests acquired						100.00%
Debt instrument term						5 years
Natural gas power facilities acquired						5
Oil-Fired power facilities						1
Coal-Fired power facilities						5
Number of power facilities acquired						6,200
Purchase price, cash						2,800,000,000
Amount of unsecured senior notes						500,000,000
Subsequent Event | Duke Midwest Purchase Agreement | Revolving Credit Facility
Subsequent Event [Line Items]
Credit agreement, maximum borrowing capacity						600,000,000
Subsequent Event | Duke Midwest Purchase Agreement | Parent
Subsequent Event [Line Items]
Coal-Fired power facilities						2
Subsequent Event | Duke Midwest Purchase Agreement | Third Parties
Subsequent Event [Line Items]
Coal-Fired power facilities						3
Subsequent Event | Duke Midwest Purchase Agreement | Guarantee | Minimum
Subsequent Event [Line Items]
Contingent consideration arrangements, range of outcomes, high value						280,000,000
Subsequent Event | Duke Midwest Purchase Agreement | Guarantee | Maximum
Subsequent Event [Line Items]
Contingent consideration arrangements, range of outcomes, high value						2,800,000,000
Subsequent Event | Duke Midwest Purchase Agreement | LIBOR
Subsequent Event [Line Items]
Basis spread on variable rate						2.75%
Subsequent Event | Duke Midwest Purchase Agreement | Base Rate
Subsequent Event [Line Items]
Basis spread on variable rate						1.75%
Subsequent Event | EquiPower Acquisition
Subsequent Event [Line Items]
Debt instrument term					5 years
Subsequent Event | EquiPower Acquisition | Senior Notes 6.75%, Due 2019
Subsequent Event [Line Items]
Stated interest rate						7.38%
Subsequent Event | EquiPower Acquisition | Senior Notes 7.375%, Due 2022
Subsequent Event [Line Items]
Stated interest rate						7.63%
Subsequent Event | EquiPower Acquisition | Senior Notes 7.625%, Due 2024
Subsequent Event [Line Items]
Stated interest rate						6.75%
Subsequent Event | EquiPower Acquisition | Revolving Credit Facility
Subsequent Event [Line Items]
Credit agreement, maximum borrowing capacity					$350,000,000
Subsequent Event | EquiPower Acquisition | LIBOR
Subsequent Event [Line Items]
Basis spread on variable rate					2.75%
Subsequent Event | EquiPower Acquisition | Base Rate
Subsequent Event [Line Items]
Basis spread on variable rate					1.75%

Subsequent_Events_Debt_Acquire

Subsequent Events (Debt Acquired in Acquisition) (Details) (Subsequent Event, USD $)	Apr. 02, 2015	Apr. 01, 2015
In Millions, unless otherwise specified
Senior Notes 6.75%, Due 2019
Business Acquisition [Line Items]
Stated interest rate	6.75%	6.75%
Senior Notes 7.375%, Due 2022
Business Acquisition [Line Items]
Stated interest rate	7.38%	7.38%
Senior Notes 7.625%, Due 2024
Business Acquisition [Line Items]
Stated interest rate	7.63%	7.63%
EquiPower Acquisition | Senior Notes 6.75%, Due 2019
Business Acquisition [Line Items]
Stated interest rate	7.38%
Debt assumed in acquisition	2,100
EquiPower Acquisition | Senior Notes 7.375%, Due 2022
Business Acquisition [Line Items]
Stated interest rate	7.63%
Debt assumed in acquisition	1,750
EquiPower Acquisition | Senior Notes 7.625%, Due 2024
Business Acquisition [Line Items]
Stated interest rate	6.75%
Debt assumed in acquisition	1,250