Tennessee Valley Authority PARRS A 2029 (TVE) 10-K 17 Nov 14 2013 FY Annual report Financial data

DEI_Document

DEI Document (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Document Information [Line Items]	'
Entity Registrant Name	'Tennessee Valley Authority
Entity Central Index Key	'0001376986
Current Fiscal Year End Date	'--09-30
Entity Filer Category	'Non-accelerated Filer
Document Type	'10-K
Document Period End Date	30-Sep-14
Document Fiscal Year Focus	'2013
Document Fiscal Period Focus	'FY
Amendment Flag	'false
Entity Common Stock, Shares Outstanding	0
Entity Well-known Seasoned Issuer	'No
Entity Voluntary Filers	'No
Entity Current Reporting Status	'Yes
Entity Public Float	$0

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Operating revenues	'	'	'
Revenue from sales of electricity	$10,999	$10,829	$11,086
Other revenue	138	127	134
Total operating revenues	11,137	10,956	11,220
Operating expenses	'	'	'
Fuel	2,730	2,820	2,680
Purchased power	1,094	1,027	1,189
Operating and maintenance	3,341	3,428	3,510
Depreciation and amortization	1,843	1,680	1,919
Tax equivalents	540	548	622
Total operating expenses	9,548	9,503	9,920
Operating income	1,589	1,453	1,300
Other income (expense), net	49	44	33
Interest expense	'	'	'
Interest expense	1,344	1,394	1,444
Allowance for funds used during construction and nuclear fuel expenditures	-175	-168	-171
Net interest expense	1,169	1,226	1,273
Net income (loss)	$469	$271	$60

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Sep. 30, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Current assets	'	'
Cash and cash equivalents	$500	$1,602
Restricted cash and investments	19	33
Accounts receivable, net	1,676	1,567
Inventories, net	1,056	1,091
Regulatory assets	481	561
Other current assets	56	52
Total current assets	3,788	4,906
Property, plant, and equipment	'	'
Completed plant	47,564	47,073
Less accumulated depreciation	-24,589	-23,157
Net completed plant	22,975	23,916
Construction in progress	5,951	4,704
Nuclear fuel	1,322	1,256
Capital leases	102	47
Total property, plant, and equipment, net	30,350	29,923
Investment funds	1,981	1,701
Regulatory and other long-term assets	'	'
Regulatory assets	8,994	9,131
Other long-term assets	483	445
Total regulatory and other long-term assets	9,477	9,576
Total assets	45,596	46,106
Current liabilities	'	'
Accounts payable and accrued liabilities	2,029	1,627
Environmental cleanup costs - Kingston ash spill	21	102
Accrued interest	380	378
Current portion of leaseback obligations	75	69
Current portion of energy prepayment obligations	100	100
Regulatory liabilities	184	212
Short-term debt, net	596	2,432
Current maturities of power bonds	1,032	32
Current maturities of long-term debt of variable interest entities	32	30
Total current liabilities	4,449	4,982
Other liabilities	'	'
Post-retirement and post-employment benefit obligations	5,839	5,348
Asset retirement obligations	3,089	3,472
Other long-term liabilities	1,962	1,861
Leaseback obligations	616	692
Energy prepayment obligations	310	410
Environmental cleanup costs - Kingston ash spill	0	67
Regulatory liabilities	0	1
Total other liabilities	11,816	11,851
Long-term debt, net	'	'
Long-term power bonds, net	21,948	22,315
Long-term debt of variable interest entities	1,279	1,311
Total long-term debt, net	23,227	23,626
Total liabilities	39,492	40,459
Commitments and contingencies (Note 20)	'	'
Proprietary capital	'	'
Power program appropriation investment	258	268
Power program retained earnings	5,240	4,767
Total power program proprietary capital	5,498	5,035
Nonpower programs appropriation investment, net	601	609
Accumulated other comprehensive income (loss)	5	3
Total proprietary capital	6,104	5,647
Total liabilities and proprietary capital	$45,596	$46,106

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities	'	'	'
Net income (loss)	$469	$271	$60
Adjustments to reconcile net income (loss) to net cash provided by operating activities	'	'	'
Depreciation and amortization (including amortization of debt issuance costs and premiums/discounts)	1,888	1,723	1,947
Amortization of nuclear fuel cost	279	268	264
Non-cash retirement benefit expense	572	622	607
Prepayment credits applied to revenue	-100	-102	-105
Fuel cost adjustment deferral	-38	97	-61
Fuel cost tax equivalents	6	2	47
Environmental cleanup costs - Kingston ash spill - non cash	68	72	73
Changes in current assets and liabilities	'	'	'
Accounts receivable, net	-79	114	89
Inventories and other current assets, net	34	27	-131
Accounts payable and accrued liabilities	147	-296	60
Accrued interest	2	1	-26
Regulatory assets costs	-56	-21	-14
Pension contributions	-256	-6	-8
Environmental cleanup costs - Kingston ash spill, net	-109	-99	-108
Insurance recoveries	175	47	5
Other, net	-22	-123	-125
Net cash provided by operating activities	2,980	2,597	2,574
Cash flows from investing activities	'	'	'
Construction expenditures	-2,384	-2,051	-2,119
Nuclear fuel expenditures	-326	-287	-361
Purchases of investments, net	-48	-48	-48
Loans and other receivables	'	'	'
Advances	-6	-6	-2
Repayments	6	9	10
Other, net	2	-2	7
Net cash used in investing activities	-2,756	-2,385	-2,513
Cash flows from financing activities	'	'	'
Issues of power bonds	989	2,122	1,126
Issues of variable interest entities	0	360	1,000
Redemptions and repurchases of power bonds	-365	-2,358	-2,717
Payments on debt of variable interest entities	-30	-13	-6
Short-term debt issues (redemptions), net	-1,837	924	1,024
Payments on leases and leasebacks	-73	-446	-84
Proceeds from call monetization	0	0	60
Financing costs, net	-4	-20	-75
Payments to U.S. Treasury	-14	-27	-27
Other, net	8	-20	-1
Net cash (used in) provided by financing activities	-1,326	522	300
Net change in cash and cash equivalents	-1,102	734	361
Cash and cash equivalents at beginning of the year	1,602	868	507
Cash and cash equivalents at end of the year	$500	$1,602	$868

CONSOLIDATED_STATEMENTS_OF_CHA

CONSOLIDATED STATEMENTS OF CHANGES IN PROPRIETARY CAPITAL (USD $)	3 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Balance at beginning of year	'	$5,647	'	$5,326	$5,647	$5,326	$5,229
Net income (loss)	322	-67	474	-245	469	271	60
Total other comprehensive income (loss)	'	'	'	'	2	77	64
Return on power program appropriation investment	'	'	'	'	-4	-7	-7
Return of power program appropriation investment	'	'	'	'	-10	-20	-20
Balance at end of year	6,104	'	5,647	'	6,104	5,647	5,326
Power Program Appropriation Investment	'	'	'	'	'	'	'
Balance at beginning of year	'	268	'	288	268	288	308
Net income (loss)	'	'	'	'	0	0	0
Total other comprehensive income (loss)	'	'	'	'	0	0	0
Return on power program appropriation investment	'	'	'	'	0	0	0
Return of power program appropriation investment	'	'	'	'	-10	-20	-20
Balance at end of year	258	'	268	'	258	268	288
Power Program Retained Earnings	'	'	'	'	'	'	'
Balance at beginning of year	'	4,767	'	4,492	4,767	4,492	4,429
Net income (loss)	'	'	'	'	477	282	70
Total other comprehensive income (loss)	'	'	'	'	0	0	0
Return on power program appropriation investment	'	'	'	'	-4	-7	-7
Return of power program appropriation investment	'	'	'	'	0	0	0
Balance at end of year	5,240	'	4,767	'	5,240	4,767	4,492
Nonpower Programs Appropriation Investment, Net	'	'	'	'	'	'	'
Balance at beginning of year	'	609	'	620	609	620	630
Net income (loss)	'	'	'	'	-8	-11	-10
Total other comprehensive income (loss)	'	'	'	'	0	0	0
Return on power program appropriation investment	'	'	'	'	0	0	0
Return of power program appropriation investment	'	'	'	'	0	0	0
Balance at end of year	601	'	609	'	601	609	620
Accumulated Other Comprehensive Income (Loss) Net Gains (Losses) on Cash Flow Hedges	'	'	'	'	'	'	'
Balance at beginning of year	'	3	'	-74	3	-74	-138
Net income (loss)	'	'	'	'	0	0	0
Total other comprehensive income (loss)	'	'	'	'	2	77	64
Return on power program appropriation investment	'	'	'	'	0	0	0
Return of power program appropriation investment	'	'	'	'	0	0	0
Balance at end of year	$5	'	$3	'	$5	$3	($74)

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) Statement (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]	'	'	'
Net income (loss)	$469	$271	$60
Net unrealized gain (loss) on cash flow hedges	4	78	99
Reclassification to earnings from cash flow hedges	-2	-1	-35
Total other comprehensive income (loss)	2	77	64
Total comprehensive income (loss)	$471	$348	$124

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Summary of Significant Accounting Policies	'
	Summary of Significant Accounting Policies
	General
	The Tennessee Valley Authority ("TVA") is a corporate agency and instrumentality of the United States that was created in 1933 by legislation enacted by the United States ("U.S.") Congress in response to a request by President Franklin D. Roosevelt.  TVA was created to, among other things, improve navigation on the Tennessee River, reduce the damage from destructive flood waters within the Tennessee River system and downstream on the lower Ohio and Mississippi Rivers, further the economic development of TVA's service area in the southeastern United States, and sell the electricity generated at the facilities TVA operates.
	Today, TVA operates the nation's largest public power system and supplies power in most of Tennessee, northern Alabama, northeastern Mississippi, and southwestern Kentucky and in portions of northern Georgia, western North Carolina, and southwestern Virginia to a population of over nine million people.
	TVA also manages the Tennessee River, its tributaries, and certain shorelines to provide, among other things, year-round navigation, flood damage reduction, and affordable and reliable electricity. Consistent with these primary purposes, TVA also manages the river system and public lands to provide recreational opportunities, adequate water supply, improved water quality, cultural and natural resource protection, and economic development.
	The power program has historically been separate and distinct from the stewardship programs.  It is required to be self-supporting from power revenues and proceeds from power financings, such as proceeds from the issuance of bonds, notes, or other evidences of indebtedness ("Bonds").  Although TVA does not currently receive congressional appropriations, it is required to make annual payments to the U.S. Treasury as a return on the government's appropriation investment in TVA's power facilities (the "Power Program Appropriation Investment").  In the 1998 Energy and Water Development Appropriations Act, Congress directed TVA to fund essential stewardship activities related to its management of the Tennessee River system and nonpower or stewardship properties with power revenues in the event that there were insufficient appropriations or other available funds to pay for such activities in any fiscal year.  Congress has not provided any appropriations to TVA to fund such activities since 1999.  Consequently, during 2000, TVA began paying for essential stewardship activities primarily with power revenues, with the remainder funded with user fees and other forms of revenues derived in connection with those activities.  The activities related to stewardship properties do not meet the criteria of an operating segment under accounting principles generally accepted in the United States of America ("GAAP").  Accordingly, these assets and properties are included as part of the power program, TVA's only operating segment.
	Power rates are established by the TVA Board of Directors ("TVA Board") as authorized by the Tennessee Valley Authority Act of 1933, as amended, 16 U.S.C. §§ 831-831ee (as amended, the “TVA Act”).  The TVA Act requires TVA to charge rates for power that will produce gross revenues sufficient to provide funds for operation, maintenance, and administration of its power system; payments to states and counties in lieu of taxes ("tax equivalents"); debt service on outstanding indebtedness; payments to the U.S. Treasury in repayment of and as a return on the Power Program Appropriation Investment; and such additional margin as the TVA Board may consider desirable for investment in power system assets, retirement of outstanding Bonds in advance of maturity, additional reduction of the Power Program Appropriation Investment, and other purposes connected with TVA's power business.  In setting TVA's rates, the TVA Board is charged by the TVA Act to have due regard for the primary objectives of the TVA Act, including the objective that power shall be sold at rates as low as are feasible.  Rates set by the TVA Board are not subject to review or approval by any state or other federal regulatory body.
	Fiscal Year
	TVA's fiscal year ends September 30.  Years (2014, 2013, etc.) refer to TVA's fiscal years unless they are preceded by “CY,” in which case the references are to calendar years.
	Cost-Based Regulation
	Since the TVA Board is authorized by the TVA Act to set rates for power sold to its customers, TVA is self-regulated.  Additionally, TVA's regulated rates are designed to recover its costs.  In view of demand for electricity and the level of competition, TVA believes that rates, set at levels that will recover TVA's costs, can be charged and collected.  As a result of these factors, TVA records certain assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for non-regulated entities.  Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates.  Regulatory liabilities generally represent obligations to make refunds to customers for previous collections for costs that are not likely to be incurred or deferral of gains that will be credited to customers in future periods.  TVA assesses whether the regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, potential legislation, and changes in technology.  Based on these assessments, TVA believes the existing regulatory assets are probable of recovery.  This determination reflects the current regulatory and political environment and is subject to change in the future.  If future recovery of regulatory assets ceases to be probable, or any of the other factors described above cease to be applicable, TVA would no longer be considered to be a regulated entity and would be required to write off these costs.  All regulatory asset write offs would be required to be recognized in earnings in the period in which future recovery ceases to be probable.
	Basis of Presentation
	The accompanying consolidated financial statements, which have been prepared in accordance with GAAP, include the accounts of TVA and variable interest entities of which TVA is determined to be the primary beneficiary. See Note 9. Intercompany balances and transactions have been eliminated in consolidation.
	Use of Estimates
	The preparation of financial statements requires TVA to estimate the effects of various matters that are inherently uncertain as of the date of the consolidated financial statements.  Although the consolidated financial statements are prepared in conformity with GAAP, TVA is required to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the amounts of revenues and expenses reported during the reporting period.  Each of these estimates varies in regard to the level of judgment involved and its potential impact on TVA's financial results.  Estimates are considered critical either when a different estimate could have reasonably been used, or where changes in the estimate are reasonably likely to occur from period to period, and such use or change would materially impact TVA's financial condition, results of operations, or cash flows.
	Reclassifications
	Certain reclassifications have been made to the Consolidated Statement of Cash Flows for the year ended September 30, 2014, in the Cash flows from operating activities section as $47 million and $5 million previously reported in Environmental cleanup costs — Kingston ash spill for the years ended September 30, 2013 and 2012, respectively, were reclassified to Insurance recoveries.
	Cash and Cash Equivalents
	Cash includes cash on hand and non-interest bearing cash and deposit accounts. All highly liquid investments with original maturities of three months or less are considered cash equivalents.
	Restricted Cash and Investments
	Restricted cash and investments reflect amounts related to collateral posted with TVA by a swap counterparty.
	Allowance for Uncollectible Accounts
	The allowance for uncollectible accounts reflects TVA's estimate of probable losses inherent in its accounts and loans receivable balances.  TVA determines the allowance based on known accounts, historical experience, and other currently available information including events such as customer bankruptcy and/or a customer failing to fulfill payment arrangements after 90 days.  It also reflects TVA's corporate credit department's assessment of the financial condition of customers and the credit quality of the receivables.
	The allowance for uncollectible accounts was $1 million at September 30, 2014, and 2013, for accounts receivable.  Additionally, loans receivable of $92 million and $73 million at September 30, 2014, and 2013, respectively, were included in Accounts receivable, net and Other long-term assets and reported net of allowances for uncollectible accounts of $9 million and $10 million at September 30, 2014, and 2013, respectively.
	The following table contains information about TVA’s current estimates related to uncollectible accounts.
	Allowance for Uncollectible Accounts
	(in millions)
			Balance at beginning of year			Additions charged to expense
								Deductions			Balance at end of year
	Description
	For the year ended September 30, 2014
	Allowance for uncollectible accounts
	Receivables		$	1		$	1	$	(1	)	$	1
	Loans		10			—		(1		)	9
	Total allowances deducted from assets		$	11		$	1	$	(2	)	$	10
	For the year ended September 30, 2013
	Allowance for uncollectible accounts
	Receivables		$	7		$	—	$	(6	)	$	1
	Loans		12			—		(2		)	10
	Total allowances deducted from assets		$	19		$	—	$	(8	)	$	11
	For the year ended September 30, 2012
	Allowance for uncollectible accounts
	Receivables		$	1		$	6	$	—		$	7
	Loans		11			1		—			12
	Total allowances deducted from assets		$	12		$	7	$	—		$	19
	Revenues
	Revenues from power sales are recorded as electricity is delivered to customers. In addition to power sales invoiced and recorded during the month, TVA accrues estimated unbilled revenues for power sales provided to six customers whose billing date occurs prior to the end of the month.  Exchange power sales are presented in the accompanying consolidated statements of operations as a component of Sales of electricity. Exchange power sales are sales of excess power after meeting TVA native load and directly served requirements.  (Native load refers to the customers on whose behalf a company, by statute, franchise, regulatory requirement, or contract, has undertaken an obligation to serve.)
	From time to time TVA transfers fiber optic capacity on TVA’s network to telecommunications service carriers and local power company customers of TVA ("LPCs").  These transactions are structured as indefeasible rights of use ("IRUs"), which are the exclusive right to use a specified amount of fiber optic capacity for a specified term.  TVA accounts for the consideration received on transfers of fiber optic capacity for cash and on all of the other elements deliverable under an IRU as revenue ratably over the term of the agreement.  TVA does not recognize revenue on any contemporaneous exchanges of its fiber optic capacity for an IRU of fiber optic capacity of the counterparty to the exchange.
	TVA engages in a wide array of arrangements in addition to power sales.  TVA records revenue when it is realized or realizable and earned when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the price or fee is fixed or determinable; and collectability is reasonably assured. Revenues from activities related to TVA’s overall mission are recorded as other operating revenue versus those that are not related to the overall mission, which are recorded in Other income (expense), net.
	Inventories
	Certain Fuel, Materials, and Supplies.  Coal, oil, limestone, tire-based fuel inventories, and materials and supplies inventories are valued using an average unit cost method.  A new average cost is computed after each inventory purchase transaction, and inventory issuances are priced at the latest moving weighted average unit cost. Natural gas inventories are valued using an average cost method, and a new average cost is computed monthly.
	Allowance for Inventory Obsolescence.  TVA reviews material and supplies inventories by category and usage on a periodic basis.  Each category is assigned a probability of becoming obsolete based on the type of material and historical usage data.  Based on the estimated value of the inventory, TVA adjusts its allowance for inventory obsolescence.
	Emission Allowances.  TVA has emission allowances for sulfur dioxide ("SO2") and nitrogen oxides ("NOx") which are accounted for as inventory.  The average cost of allowances used each month is charged to operating expense based on tons of SO2 and NOx emitted during the respective compliance periods.  Allowances granted to TVA by the Environmental Protection Agency ("EPA") are recorded at zero cost.
	Property, Plant, and Equipment, and Depreciation
	Property, Plant, and Equipment. Additions to plant are recorded at cost, which includes direct and indirect costs and an allowance for funds used during construction ("AFUDC").  The cost of current repairs and minor replacements is charged to operating expense.  Nuclear fuel inventories, which are included in Property, plant, and equipment, are valued using the average cost method for raw materials and the specific identification method for nuclear fuel in a reactor.  Amortization of nuclear fuel in a reactor is calculated on a units-of-production basis and is included in fuel expense.
	Depreciation. TVA accounts for depreciation of its properties using the composite depreciation convention of accounting.  Accordingly, the original cost of property retired is charged to accumulated depreciation. Except as described below, depreciation is generally computed on a straight-line basis over the estimated service lives of the various classes of assets. Depreciation expense for the years ended September 30, 2014, 2013, and 2012 was $1.6 billion, $1.4 billion, and $1.7 billion, respectively. Depreciation expense expressed as a percentage of the average annual depreciable completed plant was 3.42 percent for 2014, 3.12 percent for 2013, and 3.78 percent for 2012.  Average depreciation rates by asset class are as follows:
	Property, Plant, and Equipment Depreciation Rates
	At September 30
	(percent)
		2014			2013		2012
	Asset Class
	Nuclear	2.9			2.86		2.71
	Coal-Fired	4.37			3.47		5.65
Hydroelectric	1.44			1.3		1.35
Gas and oil-fired	3.23			3.21		3.67
Transmission	2.76			2.76		2.99
Other	8.4			8.14		8.1
In April 2011, TVA entered into two substantively similar agreements, one with the EPA and the other with Alabama, Kentucky, North Carolina, Tennessee, and three environmental advocacy groups (collectively, the "Environmental Agreements”).  See Note 21 — Legal Proceedings — Environmental Agreements.  Under the Environmental Agreements, TVA committed, among other things, to retire, on a phased schedule, 18 coal-fired units.
Consistent with the Environmental Agreements, Units 1 and 2 at John Sevier Fossil Plant ("John Sevier") were retired
on December 31, 2012, and Units 3 and 4 were idled on December 31, 2012 and subsequently retired on June 25, 2014. Units 3 and 5 at Widows Creek Fossil Plant ("Widows Creek") were retired on July 31, 2013, and Units 1, 2, 4, and 6 at Widows Creek were retired on July 31, 2014. On October 1, 2013, Colbert Fossil Plant ("Colbert") Unit 5 and Johnsonville Fossil Plant ("Johnsonville") Units 5, 6, 9, and 10 were idled. In addition, Units 7 and 8 at Johnsonville were idled March 1, 2012, and Unit 10 at Shawnee Fossil Plant ("Shawnee") was idled in October 2010 and subsequently retired on June 30, 2014.
On November 14, 2013, the TVA Board of Directors (the "TVA Board") approved the retirement of Colbert Units 1-5 no later than June 30, 2016, and the retirement of Widows Creek Unit 8. Additionally, the TVA Board approved the retirement of Paradise Fossil Plant ("Paradise") Units 1 and 2 upon the completion of a natural gas-fired plant at the Paradise location.
On August 21, 2014, the TVA Board approved the retirement of Allen Fossil Plant ("Allen") Units 1-3 upon the completion of a natural gas-fired plant at the Allen location.
Depreciation rates are adjusted to reflect current assumptions so that the units will be fully depreciated by the applicable idle dates.  As a result of TVA's decision to idle or retire units, TVA recognized $206 million and $49 million in accelerated depreciation expense related to the units during the years ended September 30, 2014, and 2013, respectively.
Capital Lease Agreements.  Property, plant, and equipment also includes assets recorded under capital lease agreements. These primarily consist of a natural gas lateral pipeline, power production facilities, water treatment assets, and land of $102 million and $42 million at September 30, 2014 and 2013, respectively, and fuel fabrication and blending facilities of $5 million at September 30, 2013. There were no obligations for fuel fabrication and blending facilities at September 30, 2014. Amortization expense related to capital leases is included in Depreciation and amortization in TVA’s statements of operations.
Allowance for Funds Used During Construction.  AFUDC capitalized during the year ended September 30, 2014, was $175 million, as compared to $168 million capitalized during the year ended September 30, 2013.  TVA capitalizes interest as AFUDC, based on the average interest rate of TVA’s outstanding debt.  The allowance is applicable to construction in progress related to projects with (1) an expected total project cost of $1.0 billion or more, and (2) an estimated construction period of at least three years in duration. During 2012 and 2011, TVA also included certain nuclear fuel inventories in the calculation of the allowance. During 2012, the TVA Board approved a change in the AFUDC methodology which removed the inclusion of nuclear fuel from the AFUDC calculation effective October 1, 2012. The accumulated balance of costs, which is used to calculate AFUDC, averaged approximately $3.3 billion for the year ended September 30, 2014. Subsequent to August 31, 2013, the accumulated balance of costs for Bellefonte Nuclear Plant ("Bellefonte") were removed from this calculation.
Software Costs.  TVA capitalizes certain costs incurred in connection with developing or obtaining internal-use software. Capitalized software costs are included in Property, plant, and equipment on the consolidated balance sheets and are amortized primarily over five years.  At September 30, 2014 and 2013, unamortized computer software costs totaled $22 million and $5 million, respectively.  Amortization expense related to capitalized computer software costs was $31 million for each of 2014, 2013, and 2012.  Software costs that do not meet capitalization criteria are expensed as incurred.
Impairment of Assets.  TVA evaluates long-lived assets for impairment when events or changes in circumstances indicate that the carrying value of such assets may not be recoverable.  For long-lived assets, TVA bases its evaluation on impairment indicators such as the nature of the assets, the future economic benefit of the assets, any historical or future profitability measurements, and other external market conditions or factors that may be present.  If such impairment indicators are present or other factors exist that indicate that the carrying amount of an asset may not be recoverable, TVA determines whether an impairment has occurred based on an estimate of undiscounted cash flows attributable to the asset as compared with the carrying value of the asset.  If an impairment has occurred, the amount of the impairment recognized is measured as the excess of the asset’s carrying value over its fair value.  Additionally, TVA regularly evaluates construction projects.  If the project is canceled or deemed to have no future economic benefit, the project is written off as an asset impairment or, upon Board approval, reclassified as a regulatory asset.
Decommissioning Costs
TVA recognizes legal obligations associated with the future retirement of certain tangible long-lived assets.  These obligations relate to fossil fuel-fired generating plants, nuclear generating plants, hydroelectric generating plants/dams, transmission structures, and other property-related assets.  These other property-related assets include, but are not limited to, easements and coal rights.  Activities involved with retiring these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site reclamation.  Revisions to the estimates of asset retirement obligations ("AROs") are made whenever factors indicate that the timing or amounts of estimated cash flows have changed.  Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset.  See Note 8 — Nuclear Decommissioning Costs and Non-Nuclear Decommissioning Costs and Note 12.
Blended Low-Enriched Uranium Program
Under the blended low-enriched uranium ("BLEU") program, TVA, the Department of Energy ("DOE"), and certain nuclear fuel contractors have entered into agreements providing for the DOE's surplus of enriched uranium to be blended with other uranium down to a level that allows the blended uranium to be fabricated into fuel that can be used in nuclear power plants.  This blended nuclear fuel was first loaded in a Browns Ferry Nuclear Plant ("Browns Ferry") reactor in 2005 and is expected to continue to be used to reload the Browns Ferry reactors through at least 2016. BLEU fuel was loaded into Sequoyah Nuclear Plant ("Sequoyah") Unit 2 three times but is not expected to be used in the Sequoyah reactors in the future.
Under the terms of an interagency agreement between TVA and the DOE, in exchange for supplying highly enriched uranium materials to the appropriate third-party fuel processors for processing into usable BLEU fuel for TVA, the DOE participates to a degree in the savings generated by TVA’s use of this blended nuclear fuel.  The third-party fuel processors own the conversion and processing facilities and will retain title to all land, property, plant, and equipment used in the BLEU fuel program.  Over the life of the program, TVA projects that the DOE’s share of savings generated by TVA’s use of this blended nuclear fuel could result in payments to the DOE of as much as $160 million.  TVA accrues an obligation with each BLEU reload batch related to the portion of the ultimate future payments estimated to be attributable to the BLEU fuel currently in use.  During 2009, the DOE and TVA agreed that this obligation would be offset by amounts that the DOE expects to owe TVA in the future for certain decommissioning costs that TVA will pay on the DOE’s behalf.  Accordingly, TVA will remit the BLEU fuel savings amounts to the DOE, only after those future decommissioning costs have been offset against TVA’s obligation to the DOE. At September 30, 2014, TVA had paid out approximately $101 million for this program, and the obligation recorded was $16 million.
Investment Funds
Investment funds consist primarily of trust funds designated to fund nuclear decommissioning requirements (see Note 21 — Contingencies — Decommissioning Costs), non-nuclear AROs (see Note 8 — Non-Nuclear Decommissioning Costs), the Supplemental Executive Retirement Plan ("SERP") (see Note 20 — Overview of Plans and Benefits — Supplemental Executive Retirement Plan), and the Long-Term Deferred Compensation Plan ("LTDCP"). Nuclear decommissioning funds and SERP funds are invested in portfolios of securities generally designed to achieve a return in line with overall equity market performance, while asset retirement and LTDCP funds are invested in portfolios of securities generally designed to achieve a return in line with overall equity and debt market performance. The nuclear decommissioning funds, asset retirement funds, SERP funds, and LTDCP funds are all classified as trading.
Energy Prepayment Obligations and Discounts on Sales
During 2002, TVA introduced an energy prepayment program, the discounted energy units ("DEU") program.  Under this program, TVA LPCs could purchase DEUs generally in $1 million increments, and each DEU entitles the purchaser to a $.025/kilowatt-hour discount on a specified quantity of firm power over a period of years (5, 10, 15, or 20) for each kilowatt-hour in the prepaid block.  The remainder of the price of the kilowatt-hours delivered to the LPC is due upon billing.  TVA’s DEU program allowed LPCs to use cash on hand to prepay TVA for some of their power needs, providing funding to TVA and a savings to LPCs in the form of a discount on future purchases.  The LPC receives a discount on a specified volume of firm energy purchased.  The supplement to the power contract specifies the discount rate (2.5 cents per kilowatt-hour), the monthly block of kilowatt-hours to which the discount applies, the number of years (term), and contingencies upon contract termination.
TVA has not offered the DEU program since the end of 2004.  Total sales for the program since inception have been approximately $55 million.  TVA accounted for the prepayment proceeds as unearned revenue and reported the obligations to deliver power as Energy prepayment obligations and Current portion of energy prepayment obligations on the September 30, 2013 Consolidated Balance Sheet. There were no outstanding DEU liabilities at September 30, 2014.
TVA recognizes revenue as electricity is delivered to LPCs, based on the ratio of units of kilowatt-hours delivered to total units of kilowatt-hours under contract.  At September 30, 2014, all of TVA’s obligations under the DEU program had expired, and the entire approximately $55 million had been applied against power billings on a cumulative basis during the life of the program, of which less than $1 million was recognized as noncash revenue during 2014.  Approximately $2 million and $5 million were applied against power billings during 2013 and 2012, respectively.
In 2004, TVA and its largest customer, Memphis Light, Gas and Water Division ("MLGW"), entered into an energy prepayment agreement under which MLGW prepaid TVA $1.5 billion for the future costs of electricity to be delivered by TVA to MLGW over a period of 180 months.  TVA accounted for the prepayment as unearned revenue and is reporting the obligation to deliver power under this arrangement as Energy prepayment obligations and Current portion of energy prepayment obligations on the September 30, 2014 and 2013 Consolidated Balance Sheets.  TVA expects to recognize approximately $100 million of noncash revenue in each year of the arrangement as electricity is delivered to MLGW based on the ratio of units of kilowatt-hours delivered to total units of kilowatt-hours under contract.  At September 30, 2014, approximately $1.1 billion had been recognized as noncash revenue on a cumulative basis during the life of the agreement, $100 million of which was recognized as noncash revenue during each of 2014, 2013, and 2012.
Discounts, which are recorded as a reduction to electricity sales, for both programs amounted to $46 million for the year ended September 30, 2014, and $47 million for each of the years ended September 30, 2013, and 2012.
Insurance
Although TVA uses private companies to administer its healthcare plans for eligible active and retired employees not covered by Medicare, TVA does not purchase health insurance.  Third-party actuarial specialists assist TVA in determining certain liabilities for self-insured claims.  TVA recovers the costs of claims through power rates and through adjustments to the participants’ contributions to their benefit plans.  These liabilities are included in Other liabilities on the balance sheets.
The Federal Employees' Compensation Act ("FECA") governs liability to employees for service-connected injuries.  TVA purchases excess workers' compensation insurance above a self-insured retention.
TVA sponsors an Owner Controlled Insurance Program which provides workers' compensation and liability insurance for a select group of contractors performing maintenance, modifications, outage, and new construction activities at TVA facilities.
TVA purchases nuclear liability insurance, nuclear property, decommissioning, and decontamination insurance, and nuclear accidental outage insurance.  See Note 21 — Contingencies — Nuclear Insurance.
TVA purchases excess liability insurance for aviation, auto, marine, and general liability exposures.  TVA purchases property insurance for certain conventional (non-nuclear) assets.
The insurance policies are subject to the terms and conditions of the specific policy.  Each of the insurance policies purchased contains deductibles or self-insured retentions.  TVA recovers the costs of losses through power rates.
Research and Development Costs
Research and development costs are expensed when incurred.  TVA’s research programs include those related to power delivery technologies, emerging technologies (clean energy, renewables, distributed resources, and energy efficiency), technologies related to generation (fossil fuel, nuclear, and hydroelectric), and environmental technologies.
Tax Equivalents
The TVA Act requires TVA to make payments to states and counties in which TVA conducts its power operations and in which TVA has acquired power properties previously subject to state and local taxation.  The total amount of these payments is five percent of gross revenues from sales of power during the preceding year, excluding sales or deliveries to other federal agencies and off-system sales with other utilities, with a provision for minimum payments under certain circumstances. TVA calculates tax equivalent expense by subtracting the prior year fuel cost-related tax equivalent regulatory asset or liability from the payments made to the states and counties and then adds back the current year fuel cost-related tax equivalent regulatory asset or liability. Fuel cost-related tax equivalent expense is recognized in the same accounting period in which the fuel cost-related revenue is recognized.
Maintenance Costs
TVA records maintenance costs and repairs related to its property, plant, and equipment in the statements of operations as they are incurred except for the recording of certain regulatory assets for retirement and removal costs.

Impact_of_New_Accounting_Stand

Impact of New Accounting Standards and Interpretations	12 Months Ended
	Sep. 30, 2014
Accounting Changes and Error Corrections [Abstract]	'
Impact of New Accounting Standards and Interpretations	'
	Impact of New Accounting Standards and Interpretations
	The following accounting standards became effective for TVA on October 1, 2013.
	Balance Sheet. In December 2011, the Financial Accounting Standards Board ("FASB") issued guidance that requires additional disclosures relating to the rights of offset or other netting arrangements of assets and liabilities that are presented on a net or gross basis in the consolidated balance sheets. In January 2013, FASB issued additional guidance to limit the scope of the new offsetting disclosure requirements to derivatives, repurchase agreements and reverse repurchase agreements, and securities borrowing and lending transactions.  The guidance requires the disclosure of the gross amounts subject to offset, actual amounts offset in accordance with GAAP, and the related net exposure. These changes became effective for TVA on October 1, 2013, and have been applied on a retrospective basis. This guidance relates solely to enhanced disclosures in the notes to the consolidated financial statements and did not have an impact on TVA's financial condition, results of operations, or cash flows.
	Comprehensive Income. In February 2013, FASB issued guidance that requires public reporting companies under the Securities Act of 1933 to present information about reclassification adjustments from accumulated other comprehensive income (loss) ("AOCI") in their annual and interim financial statements in a single location. The guidance requires that companies present the effect of significant amounts reclassified from each component of AOCI based on its source and the income statement line items affected by the reclassification. This information may be disclosed either in a single note or parenthetically on the face of the financial statements. If a component is not required to be reclassified to net income in its entirety, companies must cross reference to the related footnote for additional information. These changes became effective for TVA on October 1, 2013, and have been applied on a prospective basis. TVA has chosen to disclose the required information in a single note. This guidance relates solely to enhanced disclosures and did not have an impact on TVA's financial condition, results of operations, or cash flows.
	The following accounting standards have been issued, but as of September 30, 2014, were not effective and had not been adopted by TVA.
	Revenue Recognition.  In May 2014, FASB issued a new revenue recognition standard that applies to revenue from contracts with customers. The standard requires that an entity recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.  The standard becomes effective for TVA on October 1, 2017, and allows for either a full retrospective or a modified retrospective application.  Early adoption of the standard is not permitted. TVA is currently evaluating the potential impact of these changes on its consolidated financial statements and related disclosures and the application method to be used.
	Liabilities. In February 2013, FASB issued ASU 2013-04, "Liabilities (Topic 405): Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation Is Fixed at the Reporting Date," which defines how entities measure obligations from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date and for which no guidance exists, except for obligations addressed within existing guidance in GAAP. The guidance also requires entities to disclose the nature and amount of the obligation as well as other information about those obligations. The standard becomes effective for TVA on October 1, 2014. Retrospective presentation for all comparative periods presented is required and early adoption is permitted. TVA has evaluated the impact of adopting this guidance and expects no material impact on TVA's financial condition, results of operations, or cash flows.

Restructuring

Restructuring	12 Months Ended
	Sep. 30, 2014
Restructuring and Related Activities [Abstract]	'
Restructuring and Related Activities Disclosure [Text Block]	'
	3.  Restructuring
	TVA is undertaking cost reduction initiatives with the goal of keeping rates low, keeping reliability high, and continuing to fulfill its broader mission of environmental stewardship and economic development. TVA’s current focus is on reducing operating and maintenance costs through further efficiency gains and streamlining the organization. The goal is to reduce TVA’s operating and maintenance costs by $500 million by 2015 as compared to its 2013 budget. As part of these cost reduction initiatives, an organizational restructuring occurred in 2014, which resulted in approximately 2,000 position reductions achieved through attrition, elimination of vacant positions, and employees leaving TVA either voluntarily or involuntarily. Certain employees were eligible for severance payments as a result of these cost reduction initiatives. Remaining amounts to be paid are included in Accounts payable and accrued liabilities on the Consolidated Balance Sheets and the 2014 restructuring expense is included in Operating and maintenance on the Consolidated Statements of Operations. The table below summarizes the activity related to severance costs:
	Severance Cost Liability
	For the year ended September 30
		2014
	Severance cost liability at beginning of period	$	—
	Liabilities incurred during the period	65
	Actual costs paid during the period	(20		)
	Severance cost liability at end of period	$	45

Accounts_Receivable_Net

Accounts Receivable, Net	12 Months Ended
	Sep. 30, 2014
Accounts Receivable, Net [Abstract]	'
Accounts Receivable, Net	'
	Accounts Receivable, Net
	Accounts receivable primarily consist of amounts due from customers for power sales.  The table below summarizes the types and amounts of TVA’s accounts receivable:
	Accounts Receivable, Net
	At September 30
		2014			2013
	Power receivables	$	1,576		$	1,495
	Other receivables	101			73
	Allowance for uncollectible accounts	(1		)	(1		)
	Accounts receivable, net	$	1,676		$	1,567

Inventories_Net

Inventories, Net	12 Months Ended
	Sep. 30, 2014
Inventory, Net [Abstract]	'
Inventories, Net	'
	Inventories, Net
	The table below summarizes the types and amounts of TVA’s inventories:
	Inventories, Net
	At September 30
		2014			2013
	Materials and supplies inventory	$	616		$	620
	Fuel inventory	473			494
	Emission allowance inventory	13			14
	Allowance for inventory obsolescence	(46		)	(37		)
	Inventories, net	$	1,056		$	1,091

Net_Completed_Plant

Net Completed Plant	12 Months Ended
	Sep. 30, 2014
Net Completed Plant [Abstract]	'
Net Completed Plant	'
	Net Completed Plant
	Net completed plant consisted of the following:
	Net Completed Plant
	At September 30
		2014						2013
		Cost		Accumulated Depreciation				Cost		Accumulated Depreciation		Net
						Net
	Coal-fired	$	14,078	$	9,065	$	5,013	$	13,847	$	8,429	$	5,418
	Gas and oil-fired	3,411		1,094		2,317		3,386		1,008		2,378
	Nuclear	18,489		9,593		8,896		18,725		9,103		9,622
	Transmission	6,519		2,683		3,836		6,300		2,562		3,738
	Hydroelectric	2,547		889		1,658		2,392		892		1,500
	Other electrical plant	1,550		885		665		1,452		792		660
	Subtotal	46,594		24,209		22,385		46,102		22,786		23,316
	Multipurpose dams	928		364		564		928		356		572
	Other stewardship	42		16		26		43		15		28
	Subtotal	970		380		590		971		371		600
	Total	$	47,564	$	24,589	$	22,975	$	47,073	$	23,157	$	23,916

Other_LongTerm_Assets

Other Long-Term Assets	12 Months Ended
	Sep. 30, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]	'
Other Long-Term Assets	'
	Other Long-Term Assets
	The table below summarizes the types and amounts of TVA’s other long-term assets:
	Other Long-Term Assets
	At September 30
		2014		2013
	EnergyRight® receivables	$	123	$	117
	Unamortized debt issue cost of power bonds	68		75
	Loans and other long-term receivables, net	87		73
	Coal contract derivative assets	—		1
	Prepaid capacity payments	58		62
	Currency swap assets, net	—		28
	Restricted cash	64		—
	Other	83		89
	Total other long-term assets	$	483	$	445
	In association with the EnergyRight® Solutions program, LPCs offer financing to end-use customers for the purchase of energy-efficient equipment. TVA purchases the resulting loans receivable from its LPCs. The loans receivable are then transferred to a third-party bank with which TVA has agreed to repay in full any loan receivable that has been in default for 180 days or more or that TVA has determined is uncollectible. Given this continuing involvement, TVA accounts for the transfer of the loans receivable as secured borrowings. The current and long-term portions of the loans receivable are reported in Accounts receivable, net and Other long-term assets, respectively, on TVA’s consolidated balance sheets. As of September 30, 2014 and September 30, 2013, the carrying amount of the loans receivable, net of discount, reported in Accounts receivable, net was approximately $33 million. See Note 11 for information regarding the associated financing obligation.

Regulatory_Assets_and_Liabilit

Regulatory Assets and Liabilities	12 Months Ended
	Sep. 30, 2014
Regulatory Assets and Liabilities Disclosure [Abstract]	'
Regulatory Assets and Liabilities	'
	Regulatory Assets and Liabilities
	Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates.  Regulatory liabilities generally represent obligations to make refunds to customers for previous collections for costs that are not likely to be incurred or deferral of gains that will be credited to customers in future periods.  Components of regulatory assets and regulatory liabilities are summarized in the table below.
	Regulatory Assets and Liabilities
	At September 30
		2014		2013
	Current regulatory assets
	Unrealized losses on commodity derivatives	$	134	$	183
	Deferred nuclear generating units	237		237
	Environmental agreements	54		73
	Fuel cost adjustment receivable	9		—
	Environmental cleanup costs – Kingston ash spill	47		68
	Total current regulatory assets	481		561
	Non-current regulatory assets
	Deferred pension costs and other post-retirement benefits costs	4,297		4,076
	Unrealized losses on interest rate derivatives	957		808
	Nuclear decommissioning costs	931		893
	Environmental cleanup costs - Kingston ash spill	421		681
	Non-nuclear decommissioning costs	645		571
	Deferred nuclear generating units	1,255		1,438
	Unrealized losses on commodity derivatives	72		139
	Environmental agreements	108		189
	Other non-current regulatory assets	308		336
	Total non-current regulatory assets	8,994		9,131
	Total regulatory assets	$	9,475	$	9,692
	Current regulatory liabilities
	Fuel cost adjustment tax equivalents	$	182	$	176
	Fuel cost adjustment liability	—		29
	Unrealized gains on commodity derivatives	2		7
	Total current regulatory liabilities	184		212
	Non-current regulatory liabilities
	Unrealized gains on commodity derivatives	—		1
	Total non-current regulatory liabilities	—		1
	Total regulatory liabilities	$	184	$	213
	Unrealized Gains (Losses) on Commodity Derivatives.  Unrealized gains (losses) on coal purchase contracts, included as part of unrealized losses on commodity derivatives, relate to the mark-to-market ("MtM") valuation of coal purchase contracts that contain options to purchase additional or lesser quantities.  These contracts qualify as derivative contracts but do not qualify for cash flow hedge accounting treatment.  As a result, TVA recognizes the changes in the market value of these derivative contracts as a regulatory liability or asset.  This treatment reflects TVA’s ability and intent to recover the cost of these commodity contracts on a settlement basis for ratemaking purposes through the fuel cost adjustment. TVA recognizes the actual cost of fuel received under these contracts in fuel expense at the time the fuel is used to generate electricity.  These contracts expire at various times through 2018.  Unrealized gains and losses on contracts with a maturity of less than one year are included as a current regulatory asset or liability on TVA's consolidated balance sheets.  See Note 15.
	Deferred gains and losses relating to TVA’s Financial Trading Program ("FTP") represent net unrealized gains and losses on swaps, futures, options, and combinations of these instruments and are also included as part of unrealized losses on commodity derivatives.  The program is used to reduce TVA’s economic risk exposure associated with purchases and sales of commodities used in electricity generation, purchases, and sales.  TVA defers all FTP MtM unrealized gains or losses as regulatory liabilities or assets, respectively, and records realized gains or losses in fuel and purchased power expense to match the delivery period of the underlying commodity product.  Net unrealized losses at September 30, 2014, and September 30, 2013, were approximately $103 million and $166 million, respectively.  This accounting treatment reflects TVA’s ability and intent to recover the cost of these commodity contracts in future periods through the fuel cost adjustment.  The current regulatory asset/liability for net unrealized gains and losses, included as part of the commodity derivatives, represents deferred gains and losses from contracts with a maturity of less than one year.
	Deferred Nuclear Generating Units and Construction Costs.  In July 2005, the TVA Board approved the amortization, and inclusion into rates, of TVA’s $3.9 billion investment in the two deferred nuclear generating units at Bellefonte over a 10-year recovery period beginning in 2006.  In August 2011, the TVA Board approved the completion of Bellefonte Unit 1. Approximately $619 million of the remaining balance in the deferred nuclear generating units regulatory asset at that date did not continue to be amortized into rates, but was to be included in the Bellefonte plant asset balance at completion. This amount had been segregated into a separate non-current regulatory asset account titled Construction costs. TVA is evaluating the completion of Bellefonte Unit 1. In the interim, work at the site has been slowed to better allocate resources on nearer-term priorities as both budget and staffing levels for the project have been reduced in the 2014 budget. TVA believes that the resulting budgeting and staffing levels should be sufficient to preserve Bellefonte for potential future development. TVA plans to utilize its integrated resource planning process to help determine how Bellefonte best supports TVA's overall efforts to continue to meet customer demand with low-cost, reliable power. In November 2013, in accordance with the regulated operations property, plant and equipment accounting guidance, the TVA Board approved the treatment of all amounts currently included in Construction in progress related to Bellefonte as a regulatory asset. Additionally, the TVA Board approved combining (1) the amounts related to Bellefonte previously included in Construction in progress, (2) the $619 million in Regulatory asset-Construction costs, and (3) the remaining amounts included in Regulatory asset-Deferred nuclear generating units into a single regulatory asset titled Deferred nuclear generating units totaling $1.5 billion at September 30, 2014. Such amounts have been classified as a Regulatory asset in the September 30, 2014 Consolidated Balance Sheet. The TVA Board approved the recovery of this asset in future rates at an amount of $237 million per year until fully recovered. The amount to be amortized over the next year is included as a current regulatory asset on TVA's consolidated balance sheets.
	Environmental Agreements.  In conjunction with the Environmental Agreements (see Note 21 — Legal Proceedings — Environmental Agreements), TVA recorded certain liabilities totaling $360 million ($290 million investment in energy efficiency projects, demand response projects, renewable energy projects, and other TVA projects; $60 million to be provided to Alabama, Kentucky, North Carolina, and Tennessee to fund environmental projects with preference for projects in the Tennessee River watershed; and $10 million in civil penalties). The TVA Board determined that these costs would be collected in customer rates in the future and, accordingly, the amounts were deferred as a regulatory asset. Through the end of 2014, $138 million has been paid with respect to energy efficiency projects, $50 million has been paid to Alabama, Kentucky, North Carolina, and Tennessee, and $10 million has been paid with respect to civil penalties. The remaining amounts will be charged to expense and recovered in rates over future periods as payments are made.
	Environmental Cleanup Costs – Kingston Ash Spill.  In August 2009, TVA began using regulatory accounting treatment to defer all actual costs incurred and expected future costs related to the Kingston Fossil Plant ("Kingston") ash spill. The TVA Board approved a plan to amortize these costs over 15 years beginning October 1, 2009. At September 30, 2009, TVA’s remediation cost estimate of $933 million was deferred as a regulatory asset. During 2010, the estimate was revised and increased by $192 million to a total estimate of $1.1 billion. The additional amount will be amortized over the remaining term. As of September 30, 2014, TVA had received insurance proceeds of $267 million, related to insurance claim settlements. The insurance proceeds are being recorded as reductions to the regulatory asset and will reduce amounts collected in future rates. Amounts included as a current regulatory asset on TVA's consolidated balance sheets represent the amount to be amortized in the next 12 months. See Note 10.
	Fuel Cost Adjustment Receivable.  The fuel cost adjustment provides a mechanism to alter rates monthly to reflect changing fuel and purchased power costs, including realized gains and losses relating to transactions under TVA’s FTP.  There is typically a lag between the occurrence of a change in fuel and purchased power costs and the reflection of the change in fuel rates.  Balances in the fuel cost adjustment regulatory accounts represent over-collected or under-collected revenues that offset fuel and purchased power costs and are recovered or refunded in fuel rates.
	Deferred Pension Costs and Other Post-retirement Benefit Costs.  TVA measures its benefit obligations related to pension and other post-retirement benefit ("OPEB") costs at each year-end balance sheet date.  TVA recognizes the funded status of the plans on TVA's consolidated balance sheets which in an unregulated environment would result in a corresponding offset to AOCI.  “Incurred cost” is a cost arising from cash paid out or an obligation to pay for an acquired asset or service, and a loss from any cause that has been sustained and for which payment has been or must be made.  In the cases of pension and OPEB costs, the unfunded obligation represents a projected liability to the employee for services rendered, and thus it meets the definition of an incurred cost.  Therefore, amounts that otherwise would be charged to AOCI for these costs are recorded as a regulatory asset since TVA has historically recovered pension and OPEB expense in rates.  Through historical and current year expense included in ratemaking, the TVA Board has demonstrated the ability and intent to include pension and OPEB costs in allowable costs and in rates for ratemaking purposes.  As a result, it is probable that future revenue will result from inclusion of the pension and OPEB regulatory assets in allowable costs for ratemaking purposes.
	TVA has classified all amounts related to unrecognized prior service costs, net actuarial gains or losses, and the funded status as regulatory assets as such amounts are probable of collection in future rates. In 2015, TVA will begin including its cash contributions to the pension plan in the rate-making formula; accordingly, beginning October 1, 2014, TVA will recognize pension costs as regulatory assets to the extent that the amount calculated under GAAP as pension expense differs from the amount TVA contributes to the pension plan.
	These regulatory assets are classified as long-term, which is consistent with the pension and post-retirement liabilities, and not amortized to the consolidated statements of operations over a specified recovery period.  They are adjusted either upward or downward each year in conjunction with the adjustments to the unfunded pension liability, as calculated by the actuaries. Ultimately this regulatory asset will be recognized in the consolidated statements of operations in the form of pension expense as the actuarial liability is eliminated in future periods. These costs are included in other non-current regulatory assets. See Note 20 — Obligations and Funded Status.
	Unrealized Losses on Interest Rate Derivatives.  TVA uses regulatory accounting treatment to defer the MtM unrealized gains and losses on certain interest rate derivative contracts to reflect that the gain or loss is included in the ratemaking formula when these contracts actually settle.  The unrealized losses on these interest rate derivatives are recorded on TVA’s consolidated balance sheets as non-current regulatory assets and the related realized gains or losses, if any, are recorded in TVA’s consolidated statements of operations.
	Nuclear Decommissioning Costs.  Nuclear decommissioning costs include: (1) certain deferred charges related to the future closure and decommissioning of TVA’s nuclear generating units under the Nuclear Regulatory Commission ("NRC") requirements, (2) recognition of changes in the liability, (3) recognition of changes in the value of TVA's Nuclear Decommissioning Trust ("NDT"), and (4) certain other deferred charges under the accounting rules for AROs.  These future costs will be funded through a combination of the NDT, future earnings on the NDT, and, if necessary, additional TVA cash contributions to the NDT and future earnings thereon.  See Note 1 — Investment Funds.  There is not a specified recovery period; therefore, the regulatory asset is classified as long-term consistent with the NDT investments and ARO liability.
	Non-Nuclear Decommissioning Costs.  Non-nuclear decommissioning costs include:  (1) certain deferred charges related to the future closure and decommissioning of TVA’s non-nuclear long-lived assets, (2) recognition of changes in the liability, (3) recognition of changes in the value of TVA’s Asset Retirement Trust ("ART"), and (4) certain other deferred charges under the accounting rules for AROs.  TVA has established the ART to more effectively segregate, manage, and invest funds to help meet future AROs.  The funds from the ART may be used, among other things, to pay the costs related to the future closure and retirement of non-nuclear long-lived assets under various legal requirements.  These future costs can be funded through a combination of investment funds already set aside in the ART, future earnings on those investment funds, and future cash contributions to the ART and future earnings thereon.  There is not a specified recovery period; therefore, the regulatory asset is classified as long-term, consistent with the ART investments and ARO liability.
	Other Non-Current Regulatory Assets. Other non-current regulatory assets consist of the following:
	Debt Reacquisition Costs.  Reacquisition expenses, call premiums, and other related costs, such as unamortized debt issue costs associated with redeemed Bond issues, are deferred and amortized (accreted) on a straight-line basis over the weighted average life of TVA’s debt portfolio.
	Nuclear Training Costs.  As a result of refurbishing and restarting Browns Ferry Unit 1 in 2007 and the construction and startup of Watts Bar Nuclear Plant ("Watts Bar") Unit 2, nuclear training costs associated with these units have been deferred as a regulatory asset and will be amortized over a cost recovery period equivalent to the expected useful life of the operating nuclear units.
	Retirement Removal Costs.  Retirement removal costs that are not legally required are capitalized into fixed assets to be depreciated consistent with the lives in the depreciation study. See Note 1 — Property, Plant, and Equipment, and Depreciation — Depreciation. The TVA Board has consistently set rates to cover the depreciation of these assets; therefore, these assets are probable of future recovery.
	Fuel Cost Adjustment Tax Equivalents.  The fuel cost adjustment includes a provision related to the current funding of the future payments TVA will make.  As TVA records the fuel cost adjustment, the percent of the calculation that relates to a future asset or liability for tax equivalent payments is recorded as a current regulatory asset or liability and paid in the following year.

Variable_Interest_Entities

Variable Interest Entities	12 Months Ended
	Sep. 30, 2014
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]	'
Variable Interest Entities	'
	Variable Interest Entities
	A VIE is an entity that either (1) has insufficient equity to permit the entity to finance its activities without additional subordinated financial support or (2) has equity investors who lack the characteristics of owning a controlling financial interest. The analysis to determine whether an entity is a VIE considers factors such as contracts with an entity, credit support for an entity, the adequacy of the equity investment of an entity, the extent of an entity's activities that either involve or are conducted on behalf of an investor with disproportionate voting rights, and the relationship of voting power to the amount of equity invested in an entity. A VIE is consolidated by its primary beneficiary. The primary beneficiary has both (i) the power to direct the activities that most significantly impact the entity's economic performance and (ii) the obligation to absorb losses or the right to receive benefits from the entity that could potentially be significant to the VIE. The determination of the primary beneficiary requires continual reassessment.
	When TVA determines that it has a variable interest in a variable interest entity, a qualitative evaluation is performed to assess which interest holders have the power to direct the activities that most significantly impact the economic performance of the entity and have the obligation to absorb losses or receive benefits that could be significant to the entity. The evaluation considers the purpose and design of the business, the risks that the business was designed to create and pass along to other entities, the activities of the business that can be directed and which party can direct them, and the expected relative impact of those activities on the economic performance of the business through its life. TVA has the power to direct the activities of an entity when it has the ability to make key operating and financing decisions, including, but not limited to, capital investment and the issuance of debt.
	Southaven
	On August 9, 2013, TVA entered into a lease financing arrangement with Southaven Combined Cycle Generation, LLC ("SCCG") for the lease by TVA of the Southaven Combined Cycle Facility ("Southaven CCF"). SCCG is a special single-purpose limited liability company formed in June 2013 to finance the Southaven CCF through a $360 million secured notes issuance (the “SCCG notes”) and the issuance of $40 million of membership interests subject to mandatory redemption. The membership interests were purchased by Seven States Southaven, LLC ("SSSL"). SHLLC is a special single-purpose entity, also formed in June 2013, established to acquire and hold the membership interests of SCCG. A non-controlling interest in SHLLC is held by a third party through nominal membership interests, to which none of the income, expenses, and cash flows of SHLLC are allocated.
	The membership interests held by SHLLC were purchased with proceeds from the issuance of $40 million of secured notes (the “SHLLC notes”) and are subject to mandatory redemption pursuant to scheduled amortizing, semi-annual payments due each August 15 and February 15, with a final payment due on August 15, 2033. The payment dates for the mandatorily redeemable membership interests are the same as those of the SHLLC notes. The sale of the SCCG notes, the membership interests in SCCG, and the SHLLC notes all closed on August 9, 2013. The SCCG notes are secured by TVA’s lease payments, and the SHLLC notes are secured by SHLLC’s investment in, and amounts receivable from, SCCG. TVA’s lease payments to SCCG are payable on the same dates as SCCG’s and SHLLC’s semi-annual debt service payments and are equal to the sum of (i) the amount of SCCG’s semi-annual debt service payments, (ii) the amount of SHLLC’s semi-annual debt service payments, and (iii) the amount of scheduled pre-determined payments to be made to Seven States Southaven, LLC on each lease payment date by SHLLC as agreed in SHLLC’s formation documents (the "Seven States Return"). In addition to the lease payments, TVA pays administrative and miscellaneous expenses incurred by SCCG and SHLLC. Certain agreements related to this transaction contain default and acceleration provisions.
	TVA participated in the design, business conduct, and financial support of SCCG and has determined that it has a direct variable interest in SCCG resulting from risk associated with the value of the Southaven CCF at the end of the lease term. Based on its analysis, TVA has determined that it is the primary beneficiary of SCCG and, as such, is required to account for the VIE on a consolidated basis.
	John Sevier
	On January 17, 2012, TVA entered into a $1.0 billion construction management agreement and lease financing arrangement with John Sevier Combined Cycle Generation LLC ("JSCCG") for the completion and lease by TVA of the John Sevier Combined Cycle Facility ("John Sevier CCF"). JSCCG is a special single-purpose limited liability company formed in January 2012 to finance the John Sevier CCF through a $900 million secured note issuance (the “JSCCG notes”) and the issuance of $100 million of membership interests subject to mandatory redemption.  The membership interests were purchased by John Sevier Holdco LLC ("Holdco").  Holdco is a special single-purpose entity, also formed in January 2012, established to acquire and hold the membership interests in JSCCG.  A non-controlling interest in Holdco is held by a third party through nominal membership interests, to which none of the income, expenses, and cash flows is allocated.
	The membership interests held by Holdco in JSCCG were purchased with proceeds from the issuance of $100 million of secured notes (the “Holdco notes") and are subject to mandatory redemption pursuant to scheduled amortizing, semi-annual payments due each January 15 and July 15, with a final payment due on January 15, 2042. The payment dates for the mandatorily redeemable membership interests are the same as those of the Holdco notes. The sale of the JSCCG notes, the membership interests in JSCCG, and the Holdco notes closed on January 17, 2012. The JSCCG notes are secured by TVA’s lease payments, and the Holdco notes are secured by Holdco's investment in, and amounts receivable from, JSCCG. TVA’s lease payments to JSCCG are equal to and payable on the same dates as JSCCG’s and Holdco’s semi-annual debt service payments. In addition to the lease payments, TVA pays administrative and miscellaneous expenses incurred by JSCCG and Holdco. Certain agreements related to this transaction contain default and acceleration provisions.
	Due to its participation in the design, business conduct, and credit and financial support of JSCCG and Holdco, TVA has determined that it has a variable interest in each of these entities. Based on its analysis, TVA has concluded that it is the primary beneficiary of JSCCG and Holdco and, as such, is required to account for the VIEs on a consolidated basis. Holdco’s membership interests in JSCCG are eliminated in consolidation.
	The financial statement items attributable to carrying amounts and classifications of JSCCG, Holdco, and SCCG as of September 30, 2014 and 2013, as reflected in the Consolidated Balance Sheets, are as follows:
	Summary of Impact of VIEs on Consolidated Balance Sheets
	At September 30
		2014		2013
	Current liabilities of VIE
	Accrued interest of VIE	$	12	$	12
	Current portion of membership interests of VIE subject to mandatory redemption	2		2
	Current maturities of long-term debt of VIE	32		30
	Total current liabilities of VIE	46		44
	Other liabilities of VIE
	Membership interests of VIE subject to mandatory redemption	37		38
	Long-term debt of VIE, net
	Long-term debt of VIE	1,279		1,311
	Total liabilities of VIE	$	1,362	$	1,393
	Interest expense of $64 million, $50 million and $34 million related to debt of variable interest entities and membership interests of variable interest entity subject to mandatory redemption is included in the Consolidated Statements of Operations for the years ended September 30, 2014, 2013, and 2012, respectively.
	Creditors of the VIEs do not have any recourse to the general credit of TVA. TVA does not have any obligations to provide financial support to the VIEs other than as prescribed in the terms of the agreements related to these transactions.

Kingston_Fossil_Plant_Ash_Spil

Kingston Fossil Plant Ash Spill	12 Months Ended
	Sep. 30, 2014
Environmental Remediation Obligations [Abstract]	'
Kingston Fossil Plant Ash Spill	'
	Kingston Fossil Plant Ash Spill
	The Event
	In December 2008, one of the dredge cells at Kingston failed, and approximately five million cubic yards of water and coal fly ash flowed out of the cell. TVA is continuing cleanup and recovery efforts in conjunction with federal and state agencies.  TVA completed the removal of time-critical ash from the river during the third quarter of 2010, and removal of the remaining ash is considered to be non-time-critical.  In November 2012, the EPA and the Tennessee Department of Environment and Conservation ("TDEC") approved a plan to allow the Emory River's natural processes to remediate the remaining ash in the river, and to conduct a long-term monitoring program. TVA estimates that the physical cleanup work will be completed in the spring of 2015.  A final assessment, issuance of a completion report, and approval by the State of Tennessee and the EPA are expected to occur by the third quarter of 2015.
	Claims and Litigation
	See Note 21 — Legal Proceedings — Legal Proceedings Related to the Kingston Ash Spill and — Civil Penalty and Natural Resource Damages for the Kingston Ash Spill.
	Financial Impact
	TVA recorded an estimate of $1.1 billion for the cost of cleanup related to this event.  In August 2009, TVA began using regulatory accounting treatment to defer all actual costs already incurred and expected future costs related to the ash spill.  The cost is being charged to expense as it is collected in rates over 15 years, beginning October 1, 2009.
	Amounts spent since the event through September 30, 2014, totaled $1.1 billion.  The remaining estimated liability at September 30, 2014, was $21 million and is included in Current liabilities.
	TVA has not included the following categories of costs in the above estimate since it has been determined that these costs are currently either not probable or not reasonably estimable: penalties (other than the penalties set out in a June 2010 TDEC order), regulatory directives, natural resources damages (other than payments required under a memorandum of agreement with TDEC and the U.S. Fish and Wildlife Service establishing a process and a method for resolving the natural resource damages claim), future lawsuits, future claims, long-term environmental impact costs, final long-term disposition of the ash processing area, and costs associated with new laws and regulations.  There are certain other costs that will be incurred that have not been included in the estimate as they are appropriately accounted for in other areas of the consolidated financial statements.  Associated capital asset purchases are recorded in property, plant, and equipment.  Ash handling and disposition costs from current plant operations are recorded in operating expenses.  A portion of the dredge cell closure costs are also excluded from the estimate, as they are included in the non-nuclear ARO liability.
	Insurance
	TVA had property and excess liability insurance programs in place at the time of the Kingston ash spill.  TVA pursued claims under both the property and excess liability programs and has settled all of its property insurance claims and some of its excess liability insurance claims.  In April 2012, TVA initiated arbitration proceedings against the remaining excess liability insurance companies in accordance with the policies’ dispute resolution provisions. TVA is seeking recovery of certain costs incurred in the cleanup project, including the costs of removing ash from property or waters owned by the State of Tennessee, and related expenses. TVA has received insurance proceeds of $267 million, of which $175 million were received during the year ended September 30, 2014. The insurance proceeds are being recorded as reductions to the regulatory asset and will reduce costs collected in future rates.

Other_LongTerm_Liabilities

Other Long-Term Liabilities	12 Months Ended
	Sep. 30, 2014
Other Liabilities, Noncurrent [Abstract]	'
Other Long-Term Liabilities	'
	Other Long-Term Liabilities
	Other long-term liabilities consist primarily of liabilities related to certain derivative agreements as well as liabilities under agreements related to compliance with certain environmental regulations (see Note 21 — Legal Proceedings — Environmental Agreements). The table below summarizes the types and amounts of Other long-term liabilities:
	Other Long-Term Liabilities
	At September 30
		2014		2013
	Interest rate swap liabilities	$	1,348	$	1,199
	Environmental Agreements liability	108		190
	EnergyRight® financing obligation	152		149
	Membership interests of VIE subject to mandatory redemption	37		38
	Commodity contract derivative liabilities	17		35
	Commodity swap derivative liabilities	14		36
	Currency swap liabilities	15		15
	Other	271		199
	Total other long-term liabilities	$	1,962	$	1,861
	EnergyRight® Purchase Obligation. TVA purchases certain loans receivable from its LPCs in association with the EnergyRight® Solutions program. The loans receivable are then transferred to a third-party bank with which TVA has agreed to repay in full any loan receivable that has been in default for 180 days or more or that TVA has determined is uncollectible. Given this continuing involvement, TVA accounts for the transfer of the loans receivable as secured borrowings. The current and long-term portions of the resulting financing obligation are reported in Accounts payable and accrued liabilities and Other long-term liabilities, respectively, on TVA’s consolidated balance sheets. As of September 30, 2014 and September 30, 2013, the carrying amount of the financing obligation reported in Accounts payable and accrued liabilities was approximately $38 million and $37 million, respectively. See Note 7 for information regarding the associated loans receivable.
	Membership Interests of VIE Subject to Mandatory Redemption. On August 9, 2013, SCCG issued 100 percent of its membership interests to SHLLC for a total of $40 million. The membership interests in SCCG are mandatorily redeemable pursuant to a schedule of payments that indicates the amount of each payment and the corresponding dates on which each payment is due. The schedule requires SCCG to make semi-annual payments to SHLLC sufficient to provide returns on, as well as returns of, capital until the investment has been repaid in full, including a $4 million balloon payment as part of the final disbursement which is due on August 15, 2033. The return on capital includes the Seven States Return. These payments provide a return on investment to SHLLC of 7.0 percent, which is reflected as interest expense in the consolidated statements of operations. As of September 30, 2014 and September 30, 2013, the carrying amount of the Membership interests of VIE subject to mandatory redemption was $39 million and $40 million, respectively. As of September 30, 2014 and 2013, $2 million of this was current and included in Accounts payable and accrued liabilities.
	In the event that TVA were to choose to exercise an early buy out feature of the Southaven Facility Lease, in part or in whole, TVA must pay to SCCG amounts sufficient for SCCG to repay or partially repay on a pro rata basis the membership interests held by SHLLC, including any outstanding investment amount plus accrued but unpaid return. TVA also has the right, at any time and without any early redemption of the other portions of the Southaven Facility Lease payments due to SCCG, to fully repay SHLLC's investment, upon which repayment SHLLC will transfer the membership interests to a designee of TVA.

Asset_Retirement_Obligations

Asset Retirement Obligations	12 Months Ended
	Sep. 30, 2014
Asset Retirement Obligation Disclosure [Abstract]	'
Asset Retirement Obligations	'
	Asset Retirement Obligations
	During the year ended September 30, 2014, TVA's total ARO liability decreased $319 million.
	To estimate its decommissioning obligation related to its nuclear generating stations, TVA uses a probability-weighted, discounted cash flow model which, on a unit-by-unit basis, considers multiple outcome scenarios that include significant estimations and assumptions. Those assumptions include (1) estimates of the cost of decommissioning, (2) the method of decommissioning and the timing of the related cash flows, (3) the license period of the nuclear plant, considering the probability of license extensions, (4) cost escalation factors, and (5) the credit adjusted risk free rate to measure the obligation at the present value of the future estimated costs. Prior to June 30, 2014, TVA based its decommissioning cost estimates on cost elements prescribed by the NRC to dismantle and decommission the radioactive portion of each site with the assumption that decommissioning would occur within the first seven years after plant shut down, which approximates the DECON method of decommissioning. The DECON method requires that radioactive contamination is removed from a site and safely disposed of or decontaminated to a level that permits the site to be released for unrestricted use shortly after it ceases operation. On June 30, 2014, TVA recorded a change in estimate based on site-specific decommissioning cost studies. Additionally, TVA determined it appropriate to reflect an increase in the probability that certain of its nuclear operating licenses will be extended and that there is a probability that it will be able to delay ultimate decommissioning activities under a SAFSTOR method of decommissioning. The SAFSTOR method allows nuclear facilities to be placed and maintained in a condition that allows the facilities to be safely stored and subsequently decontaminated to levels that permit release for unrestricted use. As such, TVA ascribed probabilities to both the SAFSTOR and DECON methods of decommissioning in order to estimate its decommissioning obligation. Decommissioning cost studies will be updated for each of TVA’s nuclear units at least every five years.
	Additionally, both the nuclear and non-nuclear liabilities were increased by periodic accretion. This was partially offset by coal ash area settlement projects that were conducted during the year ended September 30, 2014. The nuclear and non-nuclear accretion were deferred as regulatory assets, and $40 million of the related regulatory assets was amortized into expense as this amount was collected in rates.
	Asset Retirement Obligation Activity
		Nuclear			Non-Nuclear			Total
	Balance at September 30, 2012	$	2,208		$	1,081		$	3,289
	Settlements (ash storage areas)	—			(37		)	(37		)
	Change in estimate (ash storage areas)	66			—			66
	Accretion (recorded to regulatory asset)	125			45			170
	Balance at September 30, 2013	$	2,399		$	1,089		$	3,488
	Settlements (ash storage areas)	—			(14		)	(14		)
	Change in estimate as a result of nuclear site-specific studies	(472		)	—			(472		)
	Change in estimate (ash storage areas)	—			(10		)	(10		)
	Accretion (recorded to regulatory asset)	125			52			177
	Balance at September 30, 2014	$	2,052		$	1,117		$	3,169		(1)
	Note
	(1) The current portion of ARO in the amount of $80 million is included in Accounts payable and accrued liabilities.

Debt_and_Other_Obligations

Debt and Other Obligations	12 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Debt and Other Obligations	'
	.  Debt and Other Obligations
	General
	The TVA Act authorizes TVA to issue Bonds in an amount not to exceed $30.0 billion at any time.  At September 30, 2014, TVA had only two types of Bonds outstanding: power bonds and discount notes.  Power bonds have maturities between one and 50 years, and discount notes have maturities of less than one year.  Power bonds and discount notes are both issued pursuant to Section 15d of the TVA Act and pursuant to the Basic Tennessee Valley Authority Power Bond Resolution adopted by the TVA Board on October 6, 1960, as amended on September 28, 1976, October 17, 1989, and March 25, 1992 (the "Basic Resolution").  Bonds are not obligations of the United States, and the United States does not guarantee the payments of principal or interest on Bonds.
	Power bonds and discount notes rank on parity and have first priority of payment out of net power proceeds, which are defined as the remainder of TVA’s gross power revenues after deducting the costs of operating, maintaining, and administering its power properties and tax equivalent payments, but before deducting depreciation accruals or other charges representing the amortization of capital expenditures, plus the net proceeds from the sale or other disposition of any power facility or interest therein.
	TVA considers its scheduled rent payments under its leaseback transactions, as well as its scheduled payments under its lease financing arrangements involving John Sevier CCF and Southaven CCF, as costs of operating, maintaining, and administering its power properties; however, such treatment is not free from doubt. Costs of operating, maintaining, and administering TVA's power properties have priority over TVA’s payments on the Bonds.  Once net power proceeds have been applied to payments on power bonds and discount notes as well as any other Bonds that TVA may issue in the future that rank on parity with or subordinate to power bonds and discount notes, Section 2.3 of the Basic Resolution provides that the remaining net power proceeds shall be used only for minimum payments into the U.S. Treasury required by the TVA Act in repayment of, and as a return on, the Power Program Appropriation Investment, investment in power assets, additional reductions of TVA’s capital obligations, and other lawful purposes related to TVA’s power program.
	The TVA Act and the Basic Resolution each contain two bond tests: the rate test and the bondholder protection test.  Under the rate test, TVA must charge rates for power which will produce gross revenues sufficient to provide funds for, among other things, debt service on outstanding Bonds.  As of September 30, 2014, TVA was in compliance with the rate test. See Note 1 — General.  Under the bondholder protection test, TVA must, in successive five-year periods, use an amount of net power proceeds at least equal to the sum of (1) the depreciation accruals and other charges representing the amortization of capital expenditures and (2) the net proceeds from any disposition of power facilities for either the reduction of its capital obligations (including Bonds and the Power Program Appropriation Investment) or investment in power assets.
	TVA met the bondholder protection test for the five-year period ended September 30, 2010, and must next meet the bondholder protection test for the five-year period ending September 30, 2015.
	Secured Debt of VIEs
	On August 9, 2013, SCCG issued secured notes totaling $360 million that bear interest at a rate of 3.846 percent. The SCCG notes require amortizing semi-annual payments on each February 15 and August 15, and mature on August 15, 2033. Also on August 9, 2013, SCCG issued $40 million of membership interests subject to mandatory redemption. The proceeds from the secured notes issuance and the issuance of the membership interests was paid to TVA in accordance with the terms of the Southaven head lease. See Note 9 — Southaven. TVA used the proceeds from the transaction primarily to fund the acquisition of the Southaven CCF from SSSL.
	On January 17, 2012, JSCCG issued secured notes totaling $900 million in aggregate principal amount that bear interest at a rate of 4.626 percent. Also on January 17, 2012, Holdco issued secured notes totaling $100 million that bear interest at a rate of 7.1 percent. The JSCCG notes and the Holdco notes require amortizing semi-annual payments on each January 15 and July 15, and mature on January 15, 2042. The Holdco notes require a $10 million balloon payment upon maturity. See Note 9 — John Sevier. TVA used the proceeds from the transaction to meet its requirements under the TVA Act.
	Secured debt of VIEs, including current maturities, outstanding at September 30, 2014 and 2013 totaled approximately $1.3 billion.
	Short-Term Debt
	The weighted average rates applicable to short-term debt outstanding at September 30, 2014, 2013, and 2012, were nominal, 0.04 percent, and 0.09 percent, respectively.  During 2014, 2013, and 2012, the maximum outstanding balances of TVA short-term borrowings held by the public were $2.4 billion, $3.4 billion, and $3.2 billion, respectively.  For these same years, the average amounts (and weighted average interest rates) of TVA short-term borrowings were approximately $1.7 billion (0.05 percent), $1.9 billion (0.08 percent), and $1.1 billion (0.08 percent), respectively.
	Put and Call Options
	Bond issues of $515 million held by the public are redeemable in whole or in part, at TVA’s option, on call dates ranging from the present to 2020 and at call prices of 100 percent of the principal amount.  Fifteen Bond issues totaling $375 million, with maturity dates ranging from 2025 to 2043, include a “survivor’s option,” which allows for right of redemption upon the death of a beneficial owner in certain specified circumstances.  These Bonds are classified as long-term as of September 30, 2014 and 2013.
	Additionally, TVA has two issues of Putable Automatic Rate Reset Securities ("PARRS") outstanding.  After a fixed-rate period of five years, the coupon rate on the PARRS may automatically be reset downward under certain market conditions on an annual basis.  The coupon rate reset on the PARRS is based on a calculation.  For both series of PARRS, the coupon rate will reset downward on the reset date if the rate calculated is below the then-current coupon rate on the Bond.  The calculation dates, potential reset dates, and terms of the calculation are different for each series.  The coupon rate on the 1998 Series D PARRS may be reset on June 1 (annually) if the sum of the five-day average of the 30-Year Constant Maturity Treasury ("CMT") rate for the week ending the last Friday in April, plus 94 basis points, is below the then-current coupon rate.  The coupon rate on the 1999 Series A PARRS may be reset on May 1 (annually) if the sum of the five-day average of the 30-Year CMT rate for the week ending the last Friday in March, plus 84 basis points, is below the then-current coupon rate.  The coupon rates may only be reset downward, but investors may request to redeem their Bonds at par value in conjunction with a coupon rate reset for a limited period of time prior to the reset dates under certain circumstances.
	The coupon rate for the 1998 Series D PARRS, which mature in June 2028, has been reset six times, from an initial rate of 6.75 percent to the current rate of 3.830 percent.  In connection with these resets, $251 million of the Bonds have been redeemed, so that $324 million of the Bonds were outstanding at September 30, 2014.  The coupon rate for the 1999 Series A PARRS, which mature in May 2029, has been reset five times, from an initial rate of 6.50 percent to the current rate of 3.955 percent.  In connection with these resets, $255 million of the Bonds have been redeemed, so that $270 million of the Bonds were outstanding at September 30, 2014.
	Due to the contingent nature of the put option on the PARRS, TVA determines whether the PARRS should be classified as long-term debt or current maturities of long-term debt by calculating the expected reset rate for the bonds on the calculation dates, described above, which occur in the third quarter of TVA's fiscal year.  If the reset rate is less than the then-current coupon rate on the PARRS, the PARRS are included in current maturities.  Otherwise, the PARRS are included in long-term debt.  At September 30, 2014, TVA has not determined that it is probable that the reset rate will be less than than the current coupon rate on the PARRS on the calculation dates; therefore, the par amount outstanding for each series of PARRS was classified as long-term debt.
	Debt Securities Activity
	The table below summarizes the long-term debt securities activity for the period from October 1, 2012, to September 30, 2014.
	Debt Securities Activity
	For the years ended September 30
			2014				2013
	Issues
	Variable interest entities		$	—			$	360
	electronotes®		—				152
	2012 Series B(1)		—				1,000
	2013 Series A(2)		—				1,000
	2014 Series A(3)		1,000				—
	Discount on debt issues		(11		)		(30		)
	Total		$	989			$	2,482
	Redemptions/Maturities(4)
	Variable interest entities		$	30			$	13
	electronotes®		335				50
	1998 Series C		—				1,359
	1998 Series D		—				2
	1999 Series A		—				1
	2003 Series C		—				940
	2009 Series A		4				4
	2009 Series B		26				2
	Total		$	395			$	2,371
	Notes
	(1) The 2012 Series B bonds were issued at 97.49 percent of par.
	(2) The 2013 Series A bonds were issued at 99.52 percent of par.
	(3) The 2014 Series A bonds were issued at 98.94 percent of par.
	(4) All redemptions were at 100 percent of par.
	Debt Outstanding
	Total debt outstanding at September 30, 2014, and 2013, consisted of the following:
	Short-Term Debt
	At September 30
					Call/(Put) Date				2014				2013
	CUSIP or Other Identifier		Maturity				Coupon Rate
	Short-term debt, net of discounts								$	596			$	2,432
	Current maturities of long-term debt of variable interest entities issued at par								32				30
	Current maturities of power bonds issued at par
	880591EE8		11/15/14				2.25%		3				3
	880591EF5		12/15/14				3.77%		26				26
	880591DY5		6/15/15				4.38%		1,000				—
	88059TEL1		11/15/14				2.65%		3				3
	Total current maturities of power bonds issued at par								1,032				32
	Total current debt outstanding, net								$	1,660			$	2,494
	Long-Term Debt(1)
	At September 30
				Coupon			Call Date		2014 Par				2013 Par			Stock Exchange Listings
CUSIP or Other Identifier		Maturity		Rate
electronotes®(2)		05/15/2020 -		2.375 - 4.375%			2/15/2015 -		$	387			$	723		None
		2/15/43					2/15/18
880591DY5		6/15/15		4.38%					—				1,000			New York, Luxembourg
880591EE8(3)		11/15/15		2.25%					2				4			None
880591DS8		12/15/16		4.88%					524				524			New York
880591EA6		7/18/17		5.50%					1,000				1,000			New York, Luxembourg
880591CU4		12/15/17		6.25%					650				650			New York
880591EC2		4/1/18		4.50%					1,000				1,000			New York, Luxembourg
880591EQ1		10/15/18		1.75%					1,000				1,000			New York
880591EL2		2/15/21		3.88%					1,500				1,500			New York
880591DC3		6/7/21		5.81%	(4	)			324				324			New York, Luxembourg
880591EN8		8/15/22		1.88%					1,000				1,000			New York
880591ER9		9/15/24		2.88%					1,000				—			New York
880591CJ9		11/1/25		6.75%					1,350				1,350			New York, Hong Kong, Luxembourg, Singapore
880591300(5)		6/1/28		3.83%					324				324			New York
880591409(5)		5/1/29		3.96%					270				270			New York
880591DM1		5/1/30		7.12%					1,000				1,000			New York, Luxembourg
880591DP4		6/7/32		6.59%	(4	)			406				405			New York, Luxembourg
880591DV1		7/15/33		4.70%					472				472			New York, Luxembourg
880591EF5(3)		6/15/34		3.77%					388				414			None
880591DX7		6/15/35		4.65%					436				436			New York
880591CK6		4/1/36		5.98%					121				121			New York
880591CS9		4/1/36		5.88%					1,500				1,500			New York
880591CP5		1/15/38		6.15%					1,000				1,000			New York
880591ED0		6/15/38		5.50%					500				500			New York
880591EH1		9/15/39		5.25%					2,000				2,000			New York
880591EP3		12/15/42		3.50%					1,000				1,000			New York
880591DU3		6/7/43		4.96%	(4	)			243				243			New York, Luxembourg
880591CF7		7/15/45		6.24%			7/15/20		140				140			New York
880591EB4		1/15/48		4.88%					500				500			New York, Luxembourg
880591DZ2		4/1/56		5.38%					1,000				1,000			New York
880591EJ7		9/15/60		4.63%					1,000				1,000			New York
Subtotal									22,037				22,400
Unamortized discounts, premiums, and other									(89		)		(85		)
Total long-term outstanding power bonds, net									21,948				22,315
Long-term debt of variable interest entities									1,279				1,311
Total long-term debt, net									$	23,227			$	23,626
Notes
(1)  Includes net exchange losses from currency transactions of $44 million at September 30, 2014 and $43 million at September 30, 2013.
(2)  Includes one electronotes® issue with partial maturities of principal for each required annual payment.
(3)  These Bonds include partial maturities of principal for each required annual payment.
(4)  The coupon rate represents TVA’s effective interest rate.
(5)  TVA PARRS, CUSIP numbers 880591300 and 880591409, may be redeemed under certain conditions.  See Put and Call Options.
Maturities Due in the Year Ending September 30
	2015				2016				2017				2018			2019		Thereafter		Total
Long-term power bonds and long-term debt of variable interest entities including current maturities(1)	$	1,064			$	65			$	1,590			$	1,718		$	1,070	$	18,829	$	24,336
Short-term debt, net of discounts	596				—				—				—			—		—		596
Note
(1) Does not include noncash items of foreign currency exchange loss of $44 million and net discount on sale of Bonds of $89 million.
Credit Facility Agreements
TVA and the U.S. Treasury, pursuant to the TVA Act, have entered into a memorandum of understanding under which the U.S. Treasury provides TVA with a $150 million credit facility. This credit facility was renewed for fiscal year 2015 with a maturity date of September 30, 2015. Access to this credit facility or other similar financing arrangements with the U.S. Treasury has been available to TVA since the 1960s. TVA can borrow under the U.S. Treasury credit facility only if it cannot issue Bonds in the market on reasonable terms, and TVA plans to use the credit facility as a secondary source of liquidity. The interest rate on any borrowing under this facility is based on the average rate on outstanding marketable obligations of the United States with maturities from date of issue of one year or less. There were no outstanding borrowings under the facility at September 30, 2014. The availability of this credit facility may be impacted by how the U.S. government addresses the situation of approaching its debt limit.
TVA also has funding available in the form of three long-term revolving credit facilities totaling $2.5 billion. One $1.0 billion credit facility matures on June 25, 2017, another $1.0 billion credit facility matures on December 13, 2017, and the $500 million credit facility matures on April 5, 2018. The interest rate on any borrowing under these facilities varies based on market factors and the rating of TVA's senior unsecured long-term non-credit-enhanced debt. TVA is required to pay an unused facility fee on the portion of the total $2.5 billion that TVA has not borrowed or committed under letters of credit. This fee, along with letter of credit fees, may fluctuate depending on the rating of TVA's senior unsecured long-term non-credit-enhanced debt. At September 30, 2014, and September 30, 2013, there were $1.0 billion and $0.8 billion, respectively, of letters of credit outstanding under the facilities, and there were no borrowings outstanding. See Note 15 — Other Derivative Instruments — Collateral.
Lease/Leasebacks
Prior to 2004, TVA received approximately $945 million in proceeds by entering into leaseback transactions for 24 new peaking combustion turbine units ("CTs"). TVA also received approximately $389 million in proceeds by entering into a leaseback transaction for qualified technological equipment and software ("QTE") in 2003. Due to TVA's continuing involvement in the operation and maintenance of the leased units and equipment and its control over the distribution of power produced by the combustion turbine facilities during the leaseback term, TVA accounted for the lease proceeds as financing obligations. At September 30, 2014, and September 30, 2013, the outstanding leaseback obligations related to CTs and QTE were $691 million and $761 million, respectively.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Disclosure of Reclassification Amount [Text Block]	'
	14.  Accumulated Other Comprehensive Income (Loss)
	AOCI represents market valuation adjustments related to TVA’s currency swaps. The currency swaps are cash flow hedges and are the only derivatives in TVA’s portfolio that have been designated and qualify for hedge accounting treatment. TVA records exchange rate gains and losses on its foreign currency-denominated debt in net income and marks its currency swap assets and liabilities to market through other comprehensive income (loss) ("OCI"). TVA then reclassifies an amount out of AOCI into net income, offsetting the exchange gain/loss recorded on the debt. For the year-ended September 30, 2014, TVA reclassified $2 million of gains related to its cash flow hedges from AOCI to Interest expense. See Note 15.
	TVA records certain assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for non-regulated entities. As such, certain items that would generally be reported in AOCI or that would impact the statements of operations are recorded as regulatory assets or regulatory liabilities. See Note 7, Note 15 — Overview of Accounting Treatment, Note 16, and Note 20.

Risk_Management_Activities_and

Risk Management Activities and Derivative Transactions	12 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Risk Management Activities and Derivative Transactions	'
	Risk Management Activities and Derivative Transactions
	TVA is exposed to various market risks.  These market risks include risks related to commodity prices, investment prices, interest rates, currency exchange rates, inflation, and counterparty credit and performance risks.  To help manage certain of these risks, TVA has entered into various derivative transactions: commodity option contracts, forward contracts, swaps, swaptions, futures, and options on futures.  Other than certain derivative instruments in investment funds, it is TVA's policy to enter into these derivative transactions solely for hedging purposes and not for speculative purposes.
	Overview of Accounting Treatment
	TVA recognizes certain of its derivative instruments as either assets or liabilities on its consolidated balance sheets at fair value.  The accounting for changes in the fair value of these instruments depends on (1) whether TVA uses regulatory accounting to defer the derivative gains and losses, (2) whether the derivative instrument has been designated and qualifies for hedge accounting treatment, and (3) if so, the type of hedge relationship (for example, cash flow hedge).
	The following tables summarize the accounting treatment that certain of TVA's financial derivative transactions receive.
	Summary of Derivative Instruments That Receive Hedge Accounting Treatment (part 1)
	Amount of Mark-to-Market Gain (Loss) Recognized in Other Comprehensive Income (Loss)
	For the years ended September 30
	Derivatives in Cash Flow Hedging Relationship		Objective of Hedge Transaction		Accounting for Derivative		2014				2013
					Hedging Instrument
	Currency swaps		To protect against changes in cash flows caused by changes in foreign currency exchange rates (exchange rate risk)		Unrealized gains and losses are recorded in AOCI and reclassified to interest expense to the extent they are offset by gains and losses on the hedged transaction		$	4			$	78
	Summary of Derivative Instruments That Receive Hedge Accounting Treatment (part 2)
	Amount of Gain (Loss) Reclassified from OCI to Interest Expense
	For the years ended September 30
	Derivatives in Cash Flow Hedging Relationship		2014				2013
	Currency swaps		$	2			$	1
	Note
	There were no ineffective portions or amounts excluded from effectiveness testing for any of the periods presented. Based on forecasted foreign currency exchange rates, TVA expects to reclassify approximately $37 million of losses from AOCI to interest expense within the next twelve months to offset amounts anticipated to be recorded in interest expense related to exchange gain on the debt.
	Summary of Derivative Instruments That Do Not Receive Hedge Accounting Treatment
	Amount of Gain (Loss) Recognized in Income on Derivatives(1)
	For the years ended September 30
	Derivative Type		Objective of Derivative		Accounting for Derivative Instrument		2014				2013
	Interest rate swaps		To fix short-term debt variable rate to a fixed rate (interest rate risk)		MtM gains and losses are recorded as regulatory assets or liabilities until settlement, at which time the gains/losses are recognized in gain/loss on derivative contracts.(2)		$	—			$	—
	Commodity contract derivatives		To protect against fluctuations in market prices of purchased coal or natural gas  (price risk)		MtM gains and losses are recorded as regulatory assets or liabilities. Realized gains and losses due to contract settlements are recognized in fuel expense as incurred.		(64		)		(11		)
	Commodity derivatives		To protect against fluctuations in market prices of purchased commodities (price risk)		MtM gains and losses are recorded as regulatory assets or liabilities. Realized gains and losses are recognized in fuel expense or purchased power expense when the related commodity is used in production.		(43		)		(126		)
	under FTP
	Notes
	(1) All of TVA's derivative instruments that do not receive hedge accounting treatment have unrealized gains (losses) that would otherwise be recognized in income but instead are deferred as regulatory assets and liabilities. As such, there was no related gain (loss) recognized in income for these unrealized gains (losses) for the years ended 2014 and 2013.
	(2) Generally, TVA maintains a level of outstanding discount notes equal to or greater than the notional amount of the interest rate swaps. However, in September 2014 TVA issued long-term Bonds in anticipation of the maturity of other long-term debt, and used the proceeds to pay down discount notes, which caused the balance of discount notes outstanding at September 30, 2014, to fall below the notional amount of the interest rate swaps. There is no impact on the statements of operations due to the use of regulatory accounting for these items.
	Mark-to-Market Values of TVA Derivatives
	At September 30
		2014						2013
	Derivatives that Receive Hedge Accounting Treatment:
		Balance				Balance Sheet Presentation		Balance				Balance Sheet Presentation
	Currency swaps
	£200 million Sterling	$	(15	)		Other long-term liabilities		$	(15	)		Other long-term liabilities
	£250 million Sterling	56				Other long-term assets		51				Other long-term assets
	£150 million Sterling	8				Other long-term assets		10				Other long-term assets
	Derivatives that Do Not Receive Hedge Accounting Treatment:
		Balance				Balance Sheet Presentation		Balance				Balance Sheet Presentation
	Interest rate swaps
	$1.0 billion notional	(987		)		Other long-term liabilities		(886		)		Other long-term liabilities
	$476 million notional	(349		)		Other long-term liabilities		(300		)		Other long-term liabilities
	$42 million notional	(12		)		Other long-term liabilities		(13		)		Other long-term liabilities
	Commodity contract derivatives	(96		)		Other current assets $1; Other long-term liabilities $(17); Accounts payable and accrued liabilities $(80)		(141		)		Other long-term assets $1; Other current assets $2; Other long-term liabilities $(35); Accounts payable and accrued liabilities $(109)
	FTP
	Derivatives under FTP(1)	(103		)		Other current assets $(69); Other long-term liabilities $(14); Accounts payable and accrued liabilities $(20)		(166		)		Other current assets $(97); Other long-term liabilities $(36); Accounts payable and accrued liabilities $(33)
	Note
	(1)   Fair values of certain derivatives under the FTP that were in net liability positions totaling $69 million and $100 million at September 30, 2014 and September 30, 2013, respectively, are recorded in TVA's margin cash accounts in Other current assets. These derivatives are transacted with futures commission merchants, and cash deposits have been posted to the margin cash accounts held with each futures commission merchant to offset the net liability positions in full.
	Cash Flow Hedging Strategy for Currency Swaps
	To protect against exchange rate risk related to three British pound sterling denominated Bond transactions, TVA entered into foreign currency hedges at the time the Bond transactions occurred.  TVA had the following currency swaps outstanding at September 30, 2014:
	Currency Swaps Outstanding
	At September 30, 2014
	Effective Date of Currency Swap Contract		Associated TVA Bond Issues Currency Exposure		Expiration Date of Swap		Overall Effective
							Cost to TVA
	1999		£200 million		2021		5.81%
	2001		£250 million		2032		6.59%
	2003		£150 million		2043		4.96%
	When the dollar strengthens against the British pound sterling, the transaction gain on the Bond liability is offset by a currency exchange loss on the swap contract.  Conversely, when the dollar weakens against the British pound sterling, the transaction loss on the Bond liability is offset by an exchange gain on the swap contract.  All such exchange gains or losses on the Bond liability are included in Long-term debt, net.  The offsetting exchange losses or gains on the swap contracts are recognized in Accumulated other comprehensive income (loss).  If any gain (loss) were to be incurred as a result of the early termination of the foreign currency swap contract, the resulting income (expense) would be amortized over the remaining life of the associated Bond as a component of Interest expense.
	Derivatives Not Receiving Hedge Accounting Treatment
	Interest Rate Derivatives.  TVA uses regulatory accounting treatment to defer the MtM gains and losses on its interest rate swaps. The net deferred unrealized gains and losses are classified as regulatory assets or liabilities on TVA's consolidated balance sheets and are included in the ratemaking formula when the transactions settle. The values of these derivatives are included in Other long-term assets or Other long-term liabilities on the consolidated balance sheets, and realized gains and losses, if any, are included in TVA's consolidated statements of operations.
	For the years ended 2014 and 2013, the changes in market value of the interest rate derivatives resulted in deferred unrealized gains (losses) of $(149) million and $524 million, respectively.  There were no realized gains or losses for the years ended 2014 and 2013.
	Commodity Derivatives. TVA enters into certain derivative contracts for coal and natural gas that require physical delivery of the contracted quantity of the commodity. TVA marks to market all such contracts. At September 30, 2014, and September 30, 2013, TVA's coal contract derivatives had net market values of $(86) million and $(140) million, respectively, which TVA deferred as regulatory assets or liabilities on a gross basis.  At September 30, 2014, TVA's coal contract derivatives had terms of up to three years.
The total market value of natural gas derivative contracts was $(10) million at September 30, 2014, and $(1) million at September 30, 2013. At September 30, 2014, natural gas derivative contracts had terms of up to two years.
Commodity Contract Derivatives
At September 30
	2014								2013
	Number of Contracts		Notional Amount		Fair Value (MtM)				Number of Contracts		Notional Amount		Fair Value (MtM)
Coal contract derivatives	24		31 million tons		$	(86	)		19		43 million tons		$	(140	)
Natural gas contract derivatives	46		62 million mmBtu		$	(10	)		13		39 million mmBtu		$	(1	)
Derivatives Under FTP. While TVA is currently evaluating the use of financial instruments for price hedging, certain natural gas futures and swaps remain as part of the suspended FTP. TVA has a FTP under which it may purchase and sell futures, swaps, options, and combinations of these instruments (as long as they are standard in the industry) to hedge TVA’s exposure to (1) the price of natural gas, fuel oil, electricity, coal, emission allowances, nuclear fuel, and other commodities included in TVA’s fuel cost adjustment calculation, (2) the price of construction materials, and (3) contracts for goods priced in or indexed to foreign currencies. The combined transaction limit for the fuel cost adjustment and construction material transactions is $130 million (based on one-day value at risk). In addition, the maximum hedge volume for the construction material transactions is 75 percent of the underlying net notional volume of the material that TVA anticipates using in approved TVA projects, and the market value of all outstanding hedging transactions involving construction materials is limited to $100 million at the execution of any new transaction. The portfolio value at risk limit for the foreign currency transactions is $5 million and is separate and distinct from the $130 million transaction limit discussed above. TVA's policy prohibits trading financial instruments under the FTP for speculative purposes.
At September 30, 2014 and 2013, the risks hedged under the FTP were the economic risks associated with the prices of natural gas, fuel oil, and crude oil. At September 30, 2014 and 2013, TVA had no outstanding coal contract derivatives under the FTP. There were no futures contracts or options contracts outstanding under the FTP at September 30, 2014, and swap contracts under the FTP had remaining terms of three years or less.
Derivatives under Financial Trading Program
At September 30
	2014							2013
	Notional Amount			Fair Value (MtM)				Notional Amount			Fair Value (MtM)
				(in millions)							(in millions)
Natural gas (in mmBtu)
Futures contracts	—			$	—			—			$	—
Swap contracts	102,227,500			(103		)		152,922,500			(169		)
Option contracts	—			—				—			—
Natural gas financial positions	102,227,500			$	(103	)		152,922,500			$	(169	)
Fuel oil/crude oil (in barrels)
Futures contracts	—			$	—			—			$	—
Swap contracts	—			—				1,205,000			3
Option contracts	—			—				—			—
Fuel oil/crude oil financial positions	—			$	—			1,205,000			$	3
Note
Due to the right of setoff and method of settlement, TVA elects to record commodity derivatives under the FTP based on its net commodity position with the broker or other counterparty.  Notional amounts disclosed represent the net absolute value of contractual amounts.
TVA defers all FTP unrealized gains (losses) as regulatory liabilities (assets) and records realized gains or losses to match the delivery period of the derivative contract. In addition to the open commodity derivatives disclosed above, TVA had closed derivative contracts with market values of $(5) million at September 30, 2014, and $(8) million at September 30, 2013. TVA experienced the following unrealized and realized gains and losses related to the FTP at the dates and during the periods, as applicable, set forth in the tables below:
Financial Trading Program Unrealized Gains (Losses)
At September 30
FTP unrealized gains (losses) deferred as regulatory liabilities (assets)		2014				2013
Natural gas		$	(103	)		$	(169	)
Fuel oil/crude oil		—				3
Coal		—				—
Financial Trading Program Realized Gains (Losses)
For the years ended September 30
Decrease (increase) in fuel expense		2014				2013
Natural gas		$	(34	)		$	(78	)
Fuel oil/crude oil		2				4
Coal		—				(1		)
Financial Trading Program Realized Gains (Losses)
For the years ended September 30
Decrease (increase) in purchased power expense		2014				2013
Natural gas		$	(11	)		$	(51	)
Offsetting of Derivative Assets and Liabilities
The amounts of TVA's derivative instruments as reported in the Consolidated Balance Sheets as of September 30, 2014, and September 30, 2013, are shown in the table below.
	As of September 30, 2014
	Gross Amounts of Recognized Assets/Liabilities				Gross Amounts Offset in the Balance Sheet (1)				Net Amounts of Assets/Liabilities Presented in the Balance Sheet (2)
Assets
Currency swaps	$	64			$	(64	)		$	—
Commodity derivatives under FTP	51				(51		)		—
Total derivatives subject to master netting or similar arrangement	115				(115		)		—
Total derivatives not subject to master netting or similar arrangement	1				—				1
Total	$	116			$	(115	)		$	1
Liabilities
Currency swap (3)	$	(15	)		$	—			$	(15	)
Interest rate swaps (3)	(1,348		)		—				(1,348		)
Commodity derivatives under FTP	(154		)		120				(34		)
Total derivatives subject to master netting or similar arrangement	(1,517		)		120				(1,397		)
Total derivatives not subject to master netting or similar arrangement	(97		)		—				(97		)
Total	$	(1,614	)		$	120			$	(1,494	)
	As of September 30, 2013
	Gross Amounts of Recognized Assets/Liabilities				Gross Amounts Offset in the Balance Sheet (1)				Net Amounts of Assets/Liabilities Presented in the Balance Sheet (2)
Assets
Currency swaps	$	61			$	(33	)		$	28
Commodity derivatives under FTP	101				(98		)		3
Total derivatives subject to master netting or similar arrangement	162				(131		)		31
Total derivatives not subject to master netting or similar arrangement	3				—				3
Total	$	165			$	(131	)		$	34
Liabilities
Currency swap (3)	$	(15	)		$	—			$	(15	)
Interest rate swaps (3)	(1,199		)		—				(1,199		)
Commodity derivatives under FTP	(267		)		198				(69		)
Total derivatives subject to master netting or similar arrangement	(1,481		)		198				(1,283		)
Total derivatives not subject to master netting or similar arrangement	(144		)		—				(144		)
Total	$	(1,625	)		$	198			$	(1,427	)
Notes
(1) Amounts primarily include counterparty netting of derivative contracts, margin account deposits for futures commission merchants transactions, and cash collateral received or paid in accordance with the accounting guidance for derivatives and hedging transactions.
(2) There are no derivative contracts subject to a master netting arrangement or similar agreement which are not offset in the balance sheets.
(3) Letters of credit of approximately $1.0 billion and $800 million were posted as collateral at September 30, 2014 and September 30, 2013, respectively, to partially secure the liability positions of one of the currency swaps and one of the interest rate swaps in accordance with the collateral requirements for these derivatives.
Other Derivative Instruments
Investment Fund Derivatives.  Investment funds consist primarily of funds held in the NDT, ART, SERP, and LTDCP.  All securities in the trusts are classified as trading.  See Note 16 — Investments Funds for a discussion of the trusts' objectives and the types of investments included in the various trusts.  These trusts may invest in derivative instruments which may include swaps, futures, options, forwards, and other instruments.  At September 30, 2014, and September 30, 2013, the fair value of derivative instruments in these trusts was not material to TVA's consolidated financial statements.
Collateral.  TVA's interest rate swaps, currency swaps, and commodity derivatives under the FTP contain contract provisions that require a party to post collateral (in a form such as cash or a letter of credit) when the party's liability balance under the agreement exceeds a certain threshold.  At September 30, 2014, the aggregate fair value of all derivative instruments with credit-risk related contingent features that were in a liability position was $1.4 billion.  TVA's collateral obligations at September 30, 2014, under these arrangements, was $900 million, for which TVA had posted $1.0 billion in letters of credit.  These letters of credit reduce the available balance under the related credit facilities.  TVA's assessment of the risk of its nonperformance includes a reduction in its exposure under the contract as a result of this posted collateral.
For all of its derivative instruments with credit-risk related contingent features:
•	If TVA remains a majority-owned U.S. government entity but Standard & Poor's Financial Services, LLC ("S&P") or Moody's Investors Service, Inc. ("Moody's") downgrades TVA's credit rating to AA or Aa2, respectively, TVA's collateral obligations would likely increase by $22 million; and
•	If TVA ceases to be majority-owned by the U.S. government, TVA's credit rating would likely be downgraded and TVA would be required to post additional collateral.
Counterparty Credit Risk
Credit risk is the exposure to economic loss that would occur as a result of a counterparty's nonperformance of its contractual obligations.  Where exposed to counterparty credit risk, TVA analyzes the counterparty's financial condition prior to entering into an agreement, establishes credit limits, monitors the appropriateness of those limits, as well as any changes in the creditworthiness of the counterparty on an ongoing basis, and employs credit mitigation measures, such as collateral or prepayment arrangements and master purchase and sale agreements, to mitigate credit risk.
Credit of Customers.  The majority of TVA's counterparty credit risk is associated with trade accounts receivable from delivered power sales to LPCs, all located in the Tennessee Valley region.  To a lesser extent, TVA is exposed to credit risk from directly served industries and federal agencies, and from exchange power arrangements with a small number of investor-owned regional utilities, related to either delivered power or the replacement of open positions of longer-term purchased power or fuel agreements.  TVA had concentrations of accounts receivable from three customers that represented 27 percent of total outstanding accounts receivable at September 30, 2014 and 2013.
Credit of Derivative Counterparties.  TVA has entered into derivative contracts for hedging purposes, and TVA's NDT fund and qualified defined benefit pension plan have entered into derivative contracts for investment purposes.  If a counterparty to one of TVA's hedging transactions defaults, TVA might incur substantial costs in connection with entering into a replacement hedging transaction.  If a counterparty to the derivative contracts into which the NDT fund and the pension plan have entered for investment purposes defaults, the value of the investment could decline significantly or perhaps become worthless.  TVA has concentrations of credit risk from the banking and coal industries because multiple companies in these industries serve as counterparties to TVA in various derivative transactions.  At September 30, 2014, all of TVA's currency swaps, interest rate swaps, and commodity derivatives under the FTP were with counterparties whose Moody's credit rating was Baa2 or higher.  At September 30, 2014, all of TVA's coal contract derivatives were with counterparties whose Moody's credit rating, or TVA's internal analysis when such information was unavailable, was Caa1 or higher. See Derivatives Not Receiving Hedge Accounting Treatment.
TVA currently utilizes two active futures commission merchants ("FCMs") to clear commodity contracts, including futures, options, and similar financial derivatives. These transactions are executed under the FTP by the FCMs on exchanges on behalf of TVA. TVA maintains margin cash accounts with the FCMs. See notes to the Mark-to-Market Values of TVA Derivatives table.
Credit of Suppliers.  If one of TVA's fuel or purchased power suppliers fails to perform under the terms of its contract with TVA, TVA might lose the money that it paid to the supplier under the contract and have to purchase replacement fuel or power on the spot market, perhaps at a significantly higher price than TVA was entitled to pay under the contract.  In addition, TVA might not be able to acquire replacement fuel or power in a timely manner and thus might be unable to satisfy its own obligations to deliver power.  To help ensure a reliable supply of coal, TVA had coal contracts with multiple suppliers at September 30, 2014.  The contracted supply of coal is sourced from multiple geographic regions of the United States and is to be delivered via various transportation methods (for example, barge, rail, and truck).  TVA purchases the majority of its natural gas requirements from a variety of suppliers under short-term contracts.
TVA has a power purchase agreement that expires on March 31, 2032, with a supplier of electricity for 440 megawatts ("MW") of summer net capability from a lignite-fired generating plant.  TVA has determined that the supplier has the equivalent of a non-investment grade credit rating.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	Fair Value Measurements
	Fair value is determined based on the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the asset or liability's principal market, or in the absence of a principal market, the most advantageous market for the asset or liability in an orderly transaction between market participants. TVA uses market or observable inputs as the preferred source of values, followed by assumptions based on hypothetical transactions in the absence of market inputs.
	Valuation Techniques
	The measurement of fair value results in classification into a hierarchy by the inputs used to determine the fair value as follows:
	Level 1	—		Unadjusted quoted prices in active markets accessible by the reporting entity for identical assets or liabilities.  Active markets are those in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing.
	Level 2	—		Pricing inputs other than quoted market prices included in Level 1 that are based on observable market data and that are directly or indirectly observable for substantially the full term of the asset or liability.  These include quoted market prices for similar assets or liabilities, quoted market prices for identical or similar assets in markets that are not active, adjusted quoted market prices, inputs from observable data such as interest rate and yield curves, volatilities and default rates observable at commonly quoted intervals, and inputs derived from observable market data by correlation or other means.
	Level 3	—		Pricing inputs that are unobservable, or less observable, from objective sources.  Unobservable inputs are only to be used to the extent observable inputs are not available.  These inputs maintain the concept of an exit price from the perspective of a market participant and should reflect assumptions of other market participants.  An entity should consider all market participant assumptions that are available without unreasonable cost and effort.  These are given the lowest priority and are generally used in internally developed methodologies to generate management's best estimate of the fair value when no observable market data is available.
	A financial instrument's level within the fair value hierarchy (where Level 3 is the lowest and Level 1 is the highest) is based on the lowest level of input significant to the fair value measurement.
	The following sections describe the valuation methodologies TVA uses to measure different financial instruments at fair value. Except for gains and losses on SERP and LTDCP assets, all changes in fair value of these assets and liabilities have been reflected in regulatory assets, regulatory liabilities, or accumulated other comprehensive income (loss) on TVA's consolidated balance sheets, and consolidated statements of comprehensive income (loss). Except for gains and losses on SERP and LTDCP assets, there has been no impact to TVA's consolidated statements of operations or its consolidated statements of cash flows related to these fair value measurements.
	Investments Funds
	At September 30, 2014, Investment funds were composed of $2.0 billion of securities classified as trading and measured at fair value and less than $1 million of equity investments not required to be measured at fair value. Trading securities are held in the NDT, ART, SERP, and LTDCP. The NDT holds funds for the ultimate decommissioning of TVA's nuclear power plants. The ART holds funds for the costs related to the future closure and retirement of TVA's long-lived assets. TVA established a SERP for certain executives in critical positions to provide supplemental pension benefits tied to compensation that exceeds limits set by Internal Revenue Service ("IRS") rules applicable to the qualified defined benefit pension plan. The LTDCP is designed to provide long-term incentives to executives to encourage them to stay with TVA and to provide competitive levels of total compensation to such executives. The NDT and SERP are invested in securities generally designed to achieve a return in line with overall equity market performance, and the ART and LTDCP are invested in securities generally designed to achieve a return in line with overall debt and equity market performance.
	The NDT, ART, SERP, and LTDCP are composed of multiple types of investments and are managed by external institutional managers. Most U.S. and international equities, Treasury Inflation-Protected Securities, real estate investment trust securities, cash securities, and certain derivative instruments are measured based on quoted exchange prices in active markets and are classified as Level 1 valuations. Fixed-income investments, high-yield fixed-income investments, currencies, and most derivative instruments are non-exchange traded and are classified as Level 2 valuations. These measurements are based on market and income approaches with observable market inputs.
	Private partnership investments may include holdings of investments in private real estate, venture capital, buyout, mezzanine or subordinated debt, restructuring or distressed debt, and special situations through funds managed by third-party investment managers.  Investments in private partnerships generally involve a three-to-four-year period where the investor contributes capital.  This is followed by a period of distribution, typically over several years.  The investment period is generally, at a minimum, ten years or longer.  The NDT had unfunded commitments related to private partnerships of $113 million at September 30, 2014.  These investments have no redemption or limited redemption options and may also impose restrictions on the NDT’s ability to liquidate its investments.  There are no readily available quoted exchange prices for these investments.  The fair value of the investments is based on TVA’s ownership percentage of the fair value of the underlying investments as provided by the investment managers.  These investments are typically valued on a quarterly basis.  TVA’s private partnership investments are valued at net asset values ("NAV") as a practical expedient for fair value.  TVA classifies its interest in these types of investments as Level 3 within the fair value hierarchy.
	Commingled funds represent investment funds comprising multiple individual financial instruments. The commingled funds held by the NDT, ART, SERP, and LTDCP consist of either a single class of securities, such as equity, debt, or foreign currency securities, or multiple classes of securities. All underlying positions in these commingled funds are either exchange traded (Level 1) or measured using observable inputs for similar instruments (Level 2). The fair value of commingled funds is based on NAV per fund share (the unit of account), derived from the prices of the underlying securities in the funds. These commingled funds can be redeemed at the measurement date NAV and are classified as Level 1 or Level 2 valuations.
	Realized and unrealized gains and losses on trading securities are recognized in current earnings and are based on average cost. The gains and losses of the NDT and ART are subsequently reclassified to a regulatory liability or asset account in accordance with TVA's regulatory accounting policy. See Note 1 — Cost-Based Regulation. TVA recorded unrealized gains and losses related to its trading securities held as of the end of each period as follows:
		Unrealized Investment Gains (Losses)
		At September 30
		Financial Statement Presentation		2014				2013
	SERP	Other income (expense)		$	1			$	2
	LTDCP	Other income (expense)		—				—
	NDT	Regulatory asset		35				48
	ART	Regulatory asset		15				33
	Currency and Interest Rate Derivatives
	See Note 15 — Cash Flow Hedging Strategy for Currency Swaps and Derivatives Not Receiving Hedge Accounting Treatment for a discussion of the nature, purpose, and contingent features of TVA's currency and interest rate swaps. These swaps are classified as Level 2 valuations and are valued based on income approaches using observable market inputs for similar instruments.
	Commodity Contract Derivatives and Commodity Derivatives Under FTP
	Commodity Contract Derivatives. Most of these contracts are valued based on market approaches which utilize short- and mid-term market-quoted prices from an external industry brokerage service. A small number of these contracts are valued based on a pricing model using long-term price estimates from TVA's coal price forecast. To value the volume option component of applicable coal contracts, TVA uses a Black-Scholes pricing model which includes inputs from the forecast, contract-specific terms, and other market inputs. These contracts are classified as Level 3 valuations.
	Commodity Derivatives Under FTP. These contracts are valued based on market approaches which utilize Chicago Mercantile Exchange ("CME") quoted prices and other observable inputs. Futures and options contracts settled on the CME are classified as Level 1 valuations. Swap contracts are valued using a pricing model based on CME inputs and are subject to nonperformance risk outside of the exit price. These contracts are classified as Level 2 valuations.
	See Note 15 — Derivatives Not Receiving Hedge Accounting Treatment — Commodity Derivatives and — Derivatives Under FTP for a discussion of the nature and purpose of coal contracts and derivatives under TVA's FTP.
	Nonperformance Risk
	The assessment of nonperformance risk, which includes credit risk, considers changes in current market conditions, readily available information on nonperformance risk, letters of credit, collateral, other arrangements available, and the nature of master netting arrangements. TVA is a counterparty to currency swaps, interest rate swaps, commodity contracts, and other derivatives which subject TVA to nonperformance risk. Nonperformance risk on the majority of investments and certain exchange-traded instruments held by TVA is incorporated into the exit price that is derived from quoted market data that is used to mark the investment to market.
	Nonperformance risk for most of TVA's derivative instruments is an adjustment to the initial asset/liability fair value. TVA adjusts for nonperformance risk, both for TVA (for liabilities) and the counterparty (for assets), by applying credit valuation adjustments ("CVAs"). TVA determines an appropriate CVA for each applicable financial instrument based on the term of the instrument and TVA's or the counterparty's credit rating as obtained from Moody's. For companies that do not have an observable credit rating, TVA uses internal analysis to assign a comparable rating to the company. TVA discounts each financial instrument using the historical default rate (as reported by Moody’s for CY 1983 to CY 2013) for companies with a similar credit rating over a time period consistent with the remaining term of the contract. The application of CVAs resulted in a less than $1 million decrease in the fair value of assets and a $1 million decrease in the fair value of liabilities at September 30, 2014.
	The following tables set forth by level, within the fair value hierarchy, TVA's financial assets and liabilities that were measured at fair value on a recurring basis at September 30, 2014, and September 30, 2013. Financial assets and liabilities have been classified in their entirety based on the lowest level of input that is significant to the fair value measurement. TVA's assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the determination of the fair value of the assets and liabilities and their classification in the fair value hierarchy levels.
	Fair Value Measurements
	At September 30, 2014
	Assets	Quoted Prices in Active				Significant Other				Significant				Total
		Markets for				Observable Inputs				Unobservable
		Identical Assets				(Level 2)				Inputs
		(Level 1)								(Level 3)
	Investments
	Equity securities	$	162			$	—			$	—			$	162
	Debt securities
	U.S. government corporations and	46				39				—				85
	agencies
	Corporate debt securities	—				290				—				290
	Residential mortgage-backed securities	—				14				—				14
	Commercial mortgage-backed securities	—				7				—				7
	Collateralized debt obligations	—				29				—				29
	Private partnerships	—				—				214				214
	Commingled funds(2)													—
	Equity security commingled funds	40				903				—				943
	Debt security commingled funds	61				176				—				237
	Total investments	309				1,458				214				1,981
	Currency swaps(1)	—				—				—				—
	Commodity contract derivatives	—				—				1				1
	Commodity derivatives under FTP(1)
	Swap contracts	—				—				—				—
	Total commodity derivatives under FTP	—				—				—				—
	Total	$	309			$	1,458			$	215			$	1,982
	Liabilities	Quoted Prices in Active Markets for Identical Liabilities				Significant Other				Significant				Total
		(Level 1)				Observable Inputs				Unobservable
						(Level 2)				Inputs
										(Level 3)
	Currency swaps(1)	$	—			$	15			$	—			$	15
Interest rate swaps	—				1,348				—				1,348
Commodity contract derivatives	—				—				97				97
Commodity derivatives under FTP(1)
Swap contracts	—				34				—				34
Total commodity derivatives under FTP	—				34				—				34
Total	$	—			$	1,397			$	97			$	1,494
Notes
(1)  Due to the right of setoff and method of settlement, TVA elects to record commodity derivatives under the FTP based on its net commodity position with the counterparty or FCM. Deposits are made to TVA's margin cash accounts held with each FCM to offset any net liability positions in full for derivatives that are transacted with FCMs. TVA records currency swaps net of cash collateral received from or paid to the counterparty. See Note 15 — Offsetting of Derivative Assets and Liabilities.
(2) Commingled funds represent investment funds comprising multiple individual financial instruments and are classified in the table based on their existing investment portfolio as of the measurement date.  Commingled funds primarily composed of one class of security are classified in that category.
Fair Value Measurements
At September 30, 2013
Assets	Quoted Prices in Active				Significant Other				Significant				Total
	Markets for				Observable Inputs				Unobservable
	Identical Assets				(Level 2)				Inputs
	(Level 1)								(Level 3)
Investments
Equity securities	$	151			$	—			$	—			$	151
Debt securities
U.S. government corporations and	38				67				—				105
agencies
Corporate debt securities	—				255				—				255
Residential mortgage-backed securities	—				25				—				25
Commercial mortgage-backed securities	—				7				—				7
Collateralized debt obligations	—				10				—				10
Private partnerships	—				—				159				159
Commingled funds(2)													—
Equity security commingled funds	—				741				—				741
Debt security commingled funds	—				248				—				248
Total investments	189				1,353				159				1,701
Currency swaps(1)	—				28				—				28
Commodity contract derivatives	—				—				3				3
Commodity derivatives under FTP(1)
Swap contracts	—				3				—				3
Total commodity derivatives under FTP	—				3				—				3
Total	$	189			$	1,384			$	162			$	1,735
Liabilities	Quoted Prices in Active Markets for Identical Liabilities				Significant Other				Significant				Total
	(Level 1)				Observable Inputs				Unobservable
					(Level 2)				Inputs
									(Level 3)
Currency swaps(1)	$	—			$	15			$	—			$	15
Interest rate swaps	—				1,199				—				1,199
Commodity contract derivatives	—				1				143				144
Commodity derivatives under FTP(1)
Swap contracts	—				69				—				69
Total commodity derivatives under FTP	—				69				—				69
Total	$	—			$	1,284			$	143			$	1,427
Notes
(1)  Due to the right of setoff and method of settlement, TVA elects to record commodity derivatives under the FTP based on its net commodity position with the counterparty or FCM. Deposits are made to TVA's margin cash accounts held with each FCM to offset any net liability positions in full for derivatives that are transacted with FCMs. TVA records currency swaps net of cash collateral received from or paid to the counterparty. See Note 15 — Offsetting of Derivative Assets and Liabilities.
(2) Commingled funds represent investment funds comprising multiple individual financial instruments and are classified in the table based on their existing investment portfolio as of the measurement date.  Commingled funds primarily composed of one class of security are classified in that category.
TVA uses internal and external valuation specialists for the calculation of its fair value measurements classified as Level 3. Analytical testing is performed on the change in fair value measurements each period to ensure the valuation is reasonable based on changes in general market assumptions. Significant changes to the estimated data used for unobservable inputs, in isolation or combination, may result in significant variations to the fair value measurement reported.
The following table presents a reconciliation of all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3):
Fair Value Measurements Using Significant Unobservable Inputs
	Private				Commodity Contract Derivatives
	Partnerships
Balance at October 1, 2012	$	53			$	(267	)
Purchases	101				—
Issuances	—				—
Sales	(4		)		—
Settlements	—				—
Net unrealized gains (losses) deferred as regulatory assets and liabilities	9				127
Balance at September 30, 2013	159				(140		)
Purchases	39				—
Issuances	—				—
Sales	(9		)		—
Settlements	—				33
Net unrealized gains (losses) deferred as regulatory assets and liabilities	25				11
Balance at September 30, 2014	$	214			$	(96	)
There were $57 million of realized losses related to the instruments measured at fair value using significant unobservable inputs during the year ended September 30, 2014. All unrealized gains and losses related to these instruments have been reflected as increases or decreases in regulatory assets and liabilities. See Note 8.
The following table presents quantitative information related to the significant unobservable inputs used in the measurement of fair value of TVA's assets and liabilities classified as Level 3 in the fair value hierarchy:
Quantitative Information about Level 3 Fair Value Measurements
	Fair Value at September 30 2014				Valuation Technique(s)		Unobservable Inputs		Range
Assets
Commodity contract derivatives	$	1			Discounted cash flow		Credit risk		2 - 5 %	(1)
					Pricing model		Coal supply and demand		1.0 - 1.1 billion tons/year
							Long-term market prices		$11.24 - $67.07/ton
Liabilities
Commodity contract derivatives	$	97			Pricing model		Coal supply and demand		1.0 - 1.1 billion tons/year
							Long-term market prices		$11.24 - $67.07/ton
Note
(1) Applies to two contracts.
Quantitative Information about Level 3 Fair Value Measurements
	Fair Value at September 30 2013				Valuation Technique(s)		Unobservable Inputs		Range
Assets
Commodity contract derivatives	$	3			Discounted cash flow		Credit risk		21	%	(1)
					Pricing model		Coal supply and demand		0.9 - 1.0 billion tons/year
							Long-term market prices		$10.25 - $85.25/ton
Liabilities
Commodity contract derivatives	$	143			Pricing model		Coal supply and demand		0.9 - 1.0 billion tons/year
							Long-term market prices		$10.25 - $85.25/ton
Note
(1) Applies to only one contract.
Other Financial Instruments Not Recorded at Fair Value
TVA uses the methods and assumptions described below to estimate the fair value of each significant class of financial instrument. The fair market value of the financial instruments held at September 30, 2014, and September 30, 2013, may not be representative of the actual gains or losses that will be recorded when these instruments mature or are called or presented for early redemption. The estimated values of TVA's financial instruments not recorded at fair value at September 30, 2014, and September 30, 2013, were as follows:
Estimated Values of Financial Instruments Not Recorded at Fair Value
At September 30
			2014								2013
	Valuation Classification		Carrying				Fair				Carrying				Fair
			Amount				Value				Amount				Value
EnergyRight® receivables (including current portion)	Level 2		$	156			$	166			$	150			$	150
Loans and other long-term receivables, net (including current portion)	Level 2		$	92			$	81			$	73			$	67
EnergyRight® purchase obligation (including current portion)	Level 2		$	190			$	215			$	186			$	222
Unfunded loan commitments	Level 2		$	—			$	18			$	—			$	13
Membership interests of variable interest entity subject to mandatory redemption (including current portion)	Level 2		$	39			$	50			$	40			$	50
Long-term outstanding power bonds (including current maturities), net	Level 2		$	22,980			$	26,889			$	22,347			$	24,603
Long-term debt of variable interest entities (including current maturities)	Level 2		$	1,311			$	1,425			$	1,341			$	1,386
Due to the short-term maturity of Cash and cash equivalents, Restricted cash and investments, and Short-term debt, net (each considered a Level 1 valuation classification), the carrying amounts of these instruments approximate their fair values.
The fair value for loans and other long-term receivables is estimated by determining the present value of future cash flows using a discount rate equal to lending rates for similar loans made to borrowers with similar credit ratings and for similar remaining maturities, where applicable.
The fair value of long-term debt traded in the public market is determined by multiplying the par value of the debt by the indicative market price at the balance sheet date. The fair value of other long-term debt and membership interests of variable interest entity subject to mandatory redemption is estimated by determining the present value of future cash flows using current market rates for similar obligations, giving effect to credit ratings and remaining maturities.

Proprietary_Capital

Proprietary Capital	12 Months Ended
	Sep. 30, 2014
Stockholders' Equity Note [Abstract]	'
Proprietary Capital	'
	Proprietary Capital
	Appropriation Investment
	TVA’s power program and stewardship (nonpower) programs were originally funded primarily by appropriations from Congress.  In 1959, Congress passed an amendment to the TVA Act that required TVA’s power program to be self-financing from power revenues and proceeds from power program financings.  While TVA’s power program did not directly receive appropriated funds after it became self-financing, TVA continued to receive appropriations for certain multipurpose and other nonpower mission-related activities as well as for its stewardship activities.  TVA has not received any appropriations from Congress for any activities since 1999, and since that time, TVA has funded stewardship program activities primarily with power revenues.
	The 1959 amendment to the TVA Act also required TVA, beginning in 1961, to make annual payments to the U.S. Treasury from net power proceeds as a repayment of and as a return on the Power Program Appropriation Investment until an additional $1.0 billion of the Power Program Appropriation Investment has been repaid.  TVA paid $10 million for 2014 and $20 million for 2013 as a repayment of the Power Program Appropriation Investment. With the 2014 payment, TVA fulfilled its requirement to repay $1.0 billion of the Power Program Appropriation Investment. The TVA Act requires TVA to continue making payments to the U.S. Treasury as a return on the remaining $258 million of the Power Program Appropriation Investment.
	The table below summarizes TVA's activities related to appropriated funds.
	Summary of Proprietary Capital Activity
	At or for the years ended September 30
		2014						2013
	Appropriation Investment	Power Program			Nonpower			Power Program			Nonpower
					Programs						Programs
	Balance at beginning of year	$	268		$	4,351		$	288		$	4,351
	Return of power program appropriation investment	(10		)	—			(20		)	—
	Balance at end of year	258			4,351			268			4,351
	Retained Earnings
	Balance at beginning of year	4,767			(3,742		)	4,492			(3,731		)
	Net income (expense) for year	477			(8		)	282			(11		)
	Return on power program appropriation investment	(4		)	—			(7		)	—
	Balance at end of year	5,240			(3,750		)	4,767			(3,742		)
	Net proprietary capital at September 30	$	5,498		$	601		$	5,035		$	609
	Payments to the U.S. Treasury
	TVA paid the U.S. Treasury $4 million in 2014, $7 million in 2013, and $7 million in 2012 as a return on the Power Program Appropriation Investment.  The amount of the return on the Power Program Appropriation Investment is based on the Power Program Appropriation Investment balance at the beginning of that year and the computed average interest rate payable by the U.S. Treasury on its total marketable public obligations at the same date.  The interest rates payable by TVA on the Power Program Appropriation Investment were 1.97 percent, 2.10 percent, and 2.33 percent for 2014, 2013, and 2012, respectively.
	Accumulated Other Comprehensive Income (Loss)
	The items included in Accumulated other comprehensive income (loss) consist of market valuation adjustments for certain derivative instruments.  See Note 15.
	TVA records exchange rate gains and losses on debt in net income and marks its currency swap assets and liabilities to market through other comprehensive income.  TVA had unrealized gains of $4 million and $78 million in 2014 and 2013, respectively, on the mark-to-market of currency swaps. TVA then reclassifies an amount out of accumulated other comprehensive income into net income, offsetting the gain/loss from recording the exchange gain/loss on the debt.  The amounts reclassified from other comprehensive income into net income resulted in increases to net income of $2 million, $1 million, and $35 million in 2014, 2013, and 2012, respectively.  These reclassifications, coupled with the recording of the exchange gain/loss on the debt, did not have an impact on net income in 2014, 2013, and 2012.  Based on forecasted foreign currency exchange rates, TVA expects to reclassify approximately $37 million of losses from accumulated other comprehensive income to interest expense within the next twelve months to offset amounts anticipated to be recorded in interest expense related to exchange gain on the debt.

Other_Income_Expense_Net

Other Income (Expense), Net	12 Months Ended
	Sep. 30, 2014
Other Income and Expenses [Abstract]	'
Other Income (Expense), Net	'
	Other Income (Expense), Net
	Income and expenses not related to TVA’s operating activities are summarized in the following table:
	Other Income (Expense), Net
	For the years ended September 30
		2014		2013			2012
	Interest income	$	23	$	23		$	21
	External services	19		18			7
	Gains (losses) on investments	6		4			5
	Miscellaneous	1		(1		)	—
	Total other income (expense), net	$	49	$	44		$	33

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	12 Months Ended
	Sep. 30, 2014
Supplemental Cash Flow Information [Abstract]	'
Supplemental Cash Flow Information	'
	Supplemental Cash Flow Information
	Interest paid was $1.3 billion, $1.3 billion, and $1.4 billion in 2014, 2013, and 2012, respectively. These amounts differ from interest expense due to the timing of payments and interest capitalized of $175 million in 2014, $168 million in 2013, and $171 million in 2012 as a part of major capital expenditures.
	Construction in progress and Nuclear fuel expenditures included in Accounts payable and accrued liabilities at September 30, 2014, 2013, and 2012 were $391 million, $270 million, and $204 million, respectively, and are excluded from the Statements of Consolidated Cash Flows for the years ended 2014, 2013, and 2012 as non-cash investing activities.  In November 2013, in accordance with the regulated operations property, plant and equipment accounting guidance, the TVA Board approved the treatment of all amounts currently included in Construction in progress related to Bellefonte as a regulatory asset. Bellefonte amounts included in Construction expenditures for 2013 and 2012 were $162 million and $212 million, respectively.
	TVA had non-cash activity related to financing activities on the 2014, 2013, and 2012 Consolidated Statements of Cash Flows related to capital leases of $70 million, $20 million, and $6 million, respectively.
	Cash flows from futures contracts, forward contracts, option contracts, and swap contracts that are accounted for as hedges are classified in the same category as the item being hedged or on a basis consistent with the nature of the instrument.

Benefit_Plans

Benefit Plans	12 Months Ended
	Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]	'
Benefit Plans	'
	Benefit Plans
	TVA sponsors a qualified defined benefit pension plan that covers most of its full-time employees, a qualified defined contribution plan that covers most of its full-time employees, two unfunded post-retirement health care plans that provide for non-vested contributions toward the cost of eligible retirees' medical coverage, other postemployment benefits such as workers' compensation, and the SERP.
	Overview of Plans and Benefits
	Retirement Plans.  TVA sponsors a qualified defined benefit pension plan and a qualified defined contribution 401(k) plan for most of its full-time annual employees hired prior to July 1, 2014, that provides two benefit structures: the Original Benefit Structure and the Cash Balance Benefit Structure. Eligible employees initially hired on or after January 1, 1996, must participate in the Cash Balance Benefit Structure. On April 11, 2014, the Tennessee Valley Authority Retirement System ("TVARS") Board approved amendments to the qualified defined benefit plan effective June 30, 2014. These amendments closed the defined benefit plan to new employees and certain rehires hired on or after July 1, 2014. These employees will be eligible for a retirement benefit as participants in the Employer Automatic Benefit Structure and will be eligible for a defined contribution benefit in the 401(k) plan only. A summary of the benefits provided by each structure is as follows:
	•	Original Benefit Structure.  The pension benefit for a member participating in the Original Benefit Structure is based on the member’s creditable service, the member’s average monthly salary for the highest three consecutive years of eligible compensation, and a pension factor based on the member’s age and years of service, less a Social Security offset. In addition, TVA makes matching contributions of 25 cents on the dollar (up to 1.5 percent of eligible compensation) to the 401(k) plan for members participating in the Original Benefit Structure.
	•	Cash Balance Benefit Structure.  The pension benefit for a member participating in the Cash Balance Benefit Structure is based on credits accumulated in the member’s account and the member’s age.  A member’s account receives pay credits equal to six percent of his or her eligible compensation.  The account also receives interest credits at a rate set at the beginning of each calendar year equal to the change in the Consumer Price Index for All Urban Consumers ("CPI-U") plus three percent, with the provision that the rate may not be less than six percent or more than ten percent.  The interest crediting rate was six percent for calendar years 2014 and 2013. In addition, TVA makes matching contributions of 75 cents on the dollar (up to 4.5 percent of eligible compensation) to the 401(k) plan for members participating in the Cash Balance Benefit Structure.
	•	Employer Automatic Benefit Structure. Members participating in the Employer Automatic Benefit Structure receive an automatic, non-elective contribution by TVA to the 401(k) plan equal to 4.5 percent of eligible compensation and matching contributions by TVA to the 401(k) plan of 75 cents on the dollar (up to 4.5 percent of eligible compensation).
	There are two investment funds within the defined benefit pension plan: the Fixed Benefit Fund and the Variable Fund.  TVA's plan contributions are deposited in the Fixed Benefit Fund.  Eligible employees in the Original Benefit Structure and Cash Balance Benefit Structure are allowed to make voluntary contributions to either the Variable Fund, the Fixed Fund within the Fixed Benefit Fund, or both.  Employee contributions are limited to $10,000 per year per eligible employee. The pension plan pays interest at the lesser of six percent or the actuarial assumed rate of return less 0.5 percent to employees in the Fixed Fund.  Employee contributions in the Fixed Fund were credited an annual rate of interest of six percent during 2014 and 2013, resulting in credit amounts of $33 million and $36 million, respectively.  Employee contributions to the Variable Fund are invested in an S&P 500 Stock Index Fund.
	The defined benefit pension plan and the defined contribution 401(k) plan are administered by a separate legal entity, TVARS, which is governed by its own board of directors (the "TVARS Board").  Upon notification by the TVARS Board of the minimum required and recommended contributions, TVA determines the level of contribution to make to TVARS to fund the defined benefit pension plan for the upcoming fiscal year.
	In 2009, changes were made to the cost of living adjustment ("COLA") provisions of the defined benefit pension plan. The eligibility for the COLA became age 60 for employees who retire on or after January 1, 2010. In addition, the COLA was subject to caps for calendar years 2010 to 2013. As a result, the COLA for eligible retirees for the four years beginning January 1, 2010 were as follows:
	•For CY 2010, the COLA was zero.
	•For CY 2011, the COLA was 1.15 percent.
	•For CY 2012, the COLA was zero.
	•For CY 2013, the COLA was 2.3 percent.
	In CY 2014, the COLA benefit of CPI-U, capped at 5.0 percent, was restored and was 1.53 percent.
	Members of both the Original Benefit Structure and the Cash Balance Benefit Structure can also become eligible for a supplemental pension benefit based on age and years of service at retirement, which is designed to help offset the cost of retiree medical insurance.
	401(k) Plan Contributions. TVA made non-elective and matching contributions of approximately $35 million to the plan during 2014, $34 million during 2013, and $34 million during 2012.
	Supplemental Executive Retirement Plan. TVA has established a SERP for certain executives in critical positions to provide supplemental pension benefits tied to compensation that exceeds limits imposed by IRS rules applicable to the qualified defined benefit pension plan.  TVA has historically funded the annual calculated expense.
	Other Post-Retirement Benefits.  TVA sponsors two unfunded post-retirement benefit plans that provide for non-vested contributions toward the cost of certain eligible retirees’ medical coverage.  The first plan covers only certain retirees and surviving dependents who do not qualify for TVARS benefits, including the supplemental pension benefit.  The second plan is designed to place a limit on the out-of-pocket amount certain eligible retirees pay for medical coverage and provides a credit based on years of TVA service and monthly base pension amount, reduced by any TVARS supplemental pension benefits or any TVA contribution from the first plan, described above.
	Other Post-Employment Benefits.  TVA employees injured in work-related incidents are covered by the workers’ compensation program for federal employees administered through the Department of Labor by the Office of Workers’ Compensation Programs in accordance with the provisions of FECA.  FECA provides compensation and medical benefits to federal employees for permanent and temporary disability due to employment-related injury or disease.
	Accounting Mechanisms
	Regulatory Accounting.  TVA has classified all amounts related to unrecognized prior service costs, net actuarial gains or losses, and the funded status as regulatory assets as such amounts are probable of collection in future rates. In 2015, TVA began including its cash contributions to the pension plan in the rate-making formula; accordingly, on October 1, 2014, TVA began recognizing pension costs as regulatory assets to the extent that the amount calculated under GAAP as pension expense differs from the amount TVA contributes to the pension plan.
	Cost Method. TVA uses the projected unit credit cost method to determine the service cost and the projected benefit obligation for retirement, termination, and ancillary benefits.  Under this method, a “projected accrued benefit” is calculated at the beginning of the year and at the end of the year for each benefit that may be payable in the future.  The “projected accrued benefit” is based on the plan’s accrual formula and upon service at the beginning or end of the year, but it uses final average compensation, social security benefits, and other relevant factors projected to the age at which the employee is assumed to leave active service.  The projected benefit obligation is the actuarial present value of the “projected accrued benefits” at the beginning of the year for employed participants and is the actuarial present value of all benefits for other participants.  The service cost is the actuarial present value of the difference between the “projected accrued benefits” at the beginning and end of the year.
	Amortization of Net Gain or Loss.  TVA utilizes the corridor approach for gain/loss amortization.  Differences between actuarial assumptions and actual plan results are deferred and amortized into periodic cost only when the accumulated differences exceed 10 percent of the greater of the projected benefit obligation or the market-related value of plan assets.  If necessary, the excess is amortized over the average remaining service period of active employees.
	Asset Method.  TVA recognizes the impact of asset performance on pension expense over a three-year phase-in period through a “market-related” value of assets calculation.  Since the “market-related” value of assets recognizes investment gains and losses over a three-year period, the future value of assets will be impacted as previously deferred gains or losses are recognized.  The “market-related” value is used in calculating expected return on plan assets and net gain or loss for pension cost determination.
	Obligations and Funded Status
	The changes in plan obligations, assets, and funded status for the years ended September 30, 2014 and 2013, were as follows:
	Obligations and Funded Status
	For the years ended September 30
		Pension Benefits								Other Post-Retirement Benefits
		2014				2013				2014			2013
	Change in benefit obligation
	Benefit obligation at beginning of year	$	11,471			$	11,995			$	656		$	811
	Service cost	130				154				18			24
	Interest cost	558				468				32			31
	Plan participants’ contributions	28				29				—			—
	Collections(1)	—				—				93			79
	Amendments	2				4				—			—
	Actuarial loss (gain)	722				(549		)		(21		)	(163		)
	Net transfers from variable fund/401(k) plan	13				4				—			—
	Expenses paid	(6		)		(6		)		—			—
	Benefits paid	(653		)		(628		)		(126		)	(126		)
	Benefit obligation at end of year	12,265				11,471				652			656
	Change in plan assets
	Fair value of net plan assets at beginning of year	7,221				7,029				—			—
	Actual return on plan assets	648				787				—			—
	Plan participants’ contributions	28				29				—			—
	Collections(1)	—				—				93			79
	Net transfers from variable fund/401(k) plan	13				4				—			—
	Employer contributions(2)	256				6				33			47
	Expenses paid	(6		)		(6		)		—			—
	Benefits paid	(653		)		(628		)		(126		)	(126		)
	Fair value of net plan assets at end of year	7,507				7,221				—			—
	Funded status	$	(4,758	)		$	(4,250	)		$	(652	)	$	(656	)
	Notes
	(1) Collections include retiree contributions as well as federal reinsurance payments and provider discounts and rebates.
	(2) Other Post-Retirement Benefits Employer contributions are reduced by federal reinsurance payments and provider discounts and rebates.
	The pension actuarial loss above for 2014 primarily reflects the impact of the decrease in the discount rate from 5.00 percent to 4.45 percent, which increased the liability by approximately $729 million. Additional losses were due to demographic experience from the impact of TVA’s organizational restructuring in 2014. This increased the projected benefit obligation by $36 million. These losses were partially offset by the $88 million gain from the change in the retirement rates assumptions based on a five-year experience study.
	The pension actuarial gain above for 2013 primarily reflects the impact of the increase in the discount rate from 4.00 percent to 5.00 percent, which decreased the liability by approximately $1.4 billion.  The actuarial gain was partially offset by the impact of including certain retiree benefits in the pension obligation which were not considered in prior periods, which increased the 2013 liability by $705 million.
	The $21 million other post-retirement actuarial gain for 2014 was primarily due to demographic experience related to updated per capita claims costs and retiree contributions, which decreased the liability by $64 million. The change in the retirement rates assumptions provided an additional gain of $16 million. These gains were partially offset by the decrease in the discount rate from 5.05 percent to 4.50 percent and the reduction in force impact, which increased the obligation by $43 million and $17 million, respectively.
	The other post-retirement actuarial gain for 2013 primarily reflects the impact of the increase in the discount rate from 4.00 percent to 5.05 percent, which decreased the liability by $93 million. Additional gains were due to demographic experience related to per capita costs, contributions, participation rates, and changes in plan provisions, which decreased the liability by $43 million. Changes in the adjustment of the impact of the excise tax assumption decreased the liability by $33 million. These decreases in the post-retirement liability were slightly offset by the change in the COLA and mortality assumptions.
	Amounts related to these benefit plans recognized on TVA's consolidated balance sheets consist of regulatory assets that have not been recognized as components of net periodic benefit cost at September 30, 2014 and 2013, and the funded status of TVA’s benefit plans, which are included in Accounts payable and accrued liabilities and Post-retirement and post-employment benefit obligations:
	Amounts Recognized on TVA's Consolidated Balance Sheets
At September 30
	Pension Benefits								Other Post-Retirement Benefits
	2014				2013				2014			2013
Regulatory assets	$	4,157			$	3,910			$	140		$	166
Accounts payable and accrued liabilities	(5		)		(5		)		(38		)	(39		)
Pension and post-retirement benefit obligations(1)	(4,753		)		(4,245		)		(614		)	(617		)
Note
(1) Table above excludes $472 million and $486 million of post-employment benefit costs that are recorded in Post-retirement and post-employment benefit obligations on the Consolidated Balance Sheets at September 30, 2014 and 2013, respectively.
Unrecognized amounts included in regulatory assets yet to be recognized as components of accrued benefit cost at September 30 consisted of:
Post-retirement Benefit Costs Deferred as Regulatory Assets
At September 30
	Pension Benefits								Other Post-Retirement Benefits
	2014				2013				2014			2013
Unrecognized prior service cost (credit)	$	(180	)		$	(203	)		$	(39	)	$	(45	)
Unrecognized net loss	4,337				4,113				179			211
Total regulatory assets	$	4,157			$	3,910			$	140		$	166
The projected benefit obligation, accumulated benefit obligation, and fair value of plan assets for the pension plan at September 30, 2014, and 2013, were as follows:
Projected Benefit Obligations and Accumulated Benefit Obligations in Excess of Plan Assets
At September 30
	2014				2013
Projected benefit obligation	$	12,265			$	11,471
Accumulated benefit obligation	12,039				11,216
Fair value of net plan assets	7,507				7,221
The components of net periodic benefit cost and other amounts recognized as changes in regulatory assets for the years ended September 30, 2014, and 2013, were as follows:
Components of Net Periodic Benefit Cost
For the years ended September 30
	Pension Benefits											Other Post-Retirement Benefits
	2014				2013				2012			2014			2013			2012
Service cost	$	130			$	154			$	139		$	18		$	24		$	19
Interest cost	558				468				490			32			31			35
Expected return on plan assets	(435		)		(428		)		(437		)	—			—			—
Amortization of prior service credit	(21		)		(22		)		(23		)	(6		)	(6		)	(6		)
Recognized net actuarial loss	285				377				361			11			25			29
Total net periodic benefit cost recognized	$	517			$	549			$	530		$	55		$	74		$	77
The amounts in the regulatory asset that are expected to be recognized as components of net periodic benefit cost during the next fiscal year are as follows:
Expected Amortization of Regulatory Assets in 2015
At September 30, 2014
	Pension Benefits				Other Post-Retirement				Total
					Benefits
Prior service cost (credit)	$	(21	)		$	(6	)		$	(27	)
Net actuarial loss	277				8				285
Plan Assumptions
TVA’s reported costs of providing the plan benefits are impacted by numerous factors including the provisions of the plans, changing employee demographics, and various assumptions, the most significant of which are noted below.
Actuarial Assumptions
At September 30
	Pension Benefits						Other Post-Retirement Benefits
	2014			2013			2014			2013
Assumptions utilized to determine benefit obligations at September 30
Discount rate	4.45	%		5	%		4.5	%		5.05	%
Rate of compensation increase	5.7	%		5.72	%		N/A			N/A
Initial health care cost trend rate	N/A			N/A			7.5	%		8	%
Ultimate health care cost trend rate	N/A			N/A			5	%		5	%
Ultimate trend rate is reached in year beginning	N/A			N/A			2019			2019
Assumptions utilized to determine net periodic benefit cost for the years ended September 30
Discount rate	5	%		4	%		5.05	%		4	%
Expected return on plan assets	7.25	%		7.25	%		N/A			N/A
Rate of compensation increase	5.72	%		4.44	%		N/A			N/A
Initial health care cost trend rate	N/A			N/A			8	%		8.5	%
Ultimate health care cost trend rate	N/A			N/A			5	%		5	%
Ultimate trend rate is reached in year beginning	N/A			N/A			2019			2019
Discount Rate.  In selecting the assumed discount rate, TVA reviews market yields on high-quality corporate debt and long-term obligations of the U.S. Treasury and endeavors to match, through the use of a hypothetical bond portfolio, instrument maturities with the maturities of its pension obligations in accordance with the prevailing accounting standards. The selected bond portfolio is derived from a universe of high quality corporate bonds of Aa-rated quality or higher. After the bond portfolio is selected, a single interest rate is determined that equates the present value of the plan's projected benefit payments discounted at this rate with the market value of the bonds selected. Based on recent market trends, TVA decreased its discount rate used to determine the pension benefit obligation and other post-retirement benefit obligation. At September 30, 2014, the discount rates used to determine the pension and other post-retirement benefit obligations for 2014 were 4.45 percent and 4.50 percent, respectively. At September 30, 2013, the discount rates used to determine the pension and other post-retirement benefit obligations were 5.00 percent and 5.05 percent, respectively. The discount rate assumptions used to determine the obligations at year-end are used to determine the net periodic benefit costs for the following year.
Rate of Return.  The qualified defined benefit pension plan is the only plan that is funded with qualified plan
assets. In determining its expected long-term rate of return on pension plan assets, TVA uses a process that incorporates actual
historical asset class returns and an assessment of expected future performance and takes into consideration external actuarial advice and asset class factors. Asset allocations are periodically updated using the pension plan asset/liability studies, and are part of the determination of the estimates of long-term rates of return. The current asset allocation policy approved by the TVARS Board diversifies plan assets across multiple asset classes so as to minimize the risk of large losses. The asset allocation policy is designed to be dynamic in nature and responsive to change in the funded status of TVARS. Changes in the expected return rates are based on annual studies performed by third party professional investment consultants. Based upon the results from the 2014 annual study, TVA adjusted the assumption from 7.25 percent that was used to measure the 2014, 2013, and 2012 net periodic pension benefit cost, to a 7.00 percent expected rate of return that will be used to measure the 2015 net periodic benefit pension cost.
Compensation Increases.  Assumptions related to compensation increases are based on the results obtained from an actual company experience study performed during the most recent five years for plan participants.  TVA obtained an updated study in 2013 and determined that future compensation would likely increase at rates between 3.50 percent and 13.00 percent per year, depending upon the employee's age. Based upon the current active participants, the average assumed compensation increase used to determine benefit obligations for 2014 and 2013 was 5.70 percent and 5.72 percent, respectively. The average assumed compensation increase to determine net periodic pension benefit costs for 2014, 2013, and 2012 were 5.72 percent, 4.44 percent, and 4.43 percent, respectively.
Mortality.  Mortality assumptions are based on the results obtained from a recent actual company experience study performed, which included retirees as well as other plan participants. TVA obtained an updated study in 2013, which indicated an improvement in TVA's mortality experience. Accordingly, TVA adjusted the projection period for the RP-2000 Mortality Tables for males and females projected to 2022 using scale AA at September 30, 2013. Additional experience per the actuarial review in 2014 indicated that actual experience remains in line with the assumption adopted in 2013. Therefore, TVA maintained this assumption for 2014. At September 30, 2012, the projection period for the RP- 2000 Mortality Tables for males and females was projected to 2013 using scale AA.
Health Care Cost Trends. TVA reviews actual recent cost trends and projected future trends in establishing health care cost trend rates. The assumed health care trend rates used to determine post-retirement benefit obligations for 2014 and 2013 were 7.50 percent and 8.00 percent, respectively. The 2014 health care cost trend rate of 7.50 percent used to determine post-retirement benefit obligations is assumed to gradually decrease each successive year until it reaches a 5.00 percent annual increase in health care costs in the years beginning October 1, 2019, and beyond. The assumed health care cost trend rates used to determine the net periodic post-retirement cost were 8.00 percent for 2014, 8.50 percent for 2013, and 8.00 percent for 2012. TVA plans to use 7.50 percent in the determination of 2015 net periodic post-retirement cost. TVA had increased the rate from 2012 to 2013 based upon exhibited annual increases in costs per covered life due primarily to changes in inflation, utilization, and healthcare regulations. Costs in 2014 have decreased in line with the actuarial expectations as a result of plan changes and prescription drug coverage.
Cost of Living Adjustment.  COLAs are an increase in the benefits for eligible retirees to help maintain the purchasing power of benefits as consumer prices increase. Eligible retirees may receive a COLA on the base pension portion of the monthly pension benefit in January following any year in which the 12-month average CPI-U exceeded by as much as one percent the 12-month average of the CPI-U for the preceding year. The minimum COLA is one percent and the maximum is five percent. The COLA was temporarily reduced for a four-year period beginning January 1, 2010, for current retirees, and the eligibility for the COLA was changed to age 60 from attained age 55 for employees retiring on or after January 1, 2010. The COLA assumption was 2.50 percent from 2009 to 2012; however, in 2013, TVA adjusted the COLA assumption due to the Federal Reserve System’s long-term monetary policy and the market-based expectations that inflation will remain below two percent into 2015. TVA adjusted the COLA assumption at September 30, 2013, to 1.6 percent with an assumed gradual increase each successive year until it reaches 2.50 percent in 2020. At September 30, 2014, the COLA is assumed to increase to 2.0 percent with an assumed gradual increase each successive year until it reaches 2.50 percent in 2020.
Sensitivity of Costs to Changes in Assumptions.  The following chart reflects the sensitivity of pension cost to changes in certain actuarial assumptions:
Sensitivity to Certain Changes in Pension Assumptions
At September 30, 2014
		Change in Assumption			Impact on 2014 Pension Cost				Impact on 2014 Projected Benefit Obligation
Actuarial Assumption
Discount rate		(0.25	)		$	18			$	369
Rate of return on plan assets		(0.25	)		15				N/A
Each fluctuation above assumes that the other components of the calculation are held constant and excludes any impact for unamortized actuarial gains or losses.
The following chart reflects the sensitivity of post-retirement benefit cost to changes in the health care trend rate:
Sensitivity to Changes in Assumed Health Care Cost Trend Rates
At September 30, 2014
	1% Increase				1% Decrease
Effect on total of service and interest cost components for the year	$	7			$	(7	)
Effect on end-of-year accumulated post-retirement benefit obligation	89				(93		)
Each fluctuation above assumes that the other components of the calculation are held constant and excludes any impact for unamortized actuarial gains or losses.
Plan Investments
The qualified defined benefit pension plan (the "Plan"), which includes the Original Benefit Structure and the Cash Balance Benefit Structure, is the only plan that includes qualified plan assets. TVARS has a long-term investment plan which contains a dynamic de-risking strategy that allocates investments to assets that better match the liability, such as long duration fixed income securities, over time as funding status targets are met. The investment asset allocation policy approved by the TVARS Board has targets of 47 percent equity including U.S., non-U.S., private, and low volatility global public equity investments, 28 percent fixed income securities, 15 percent public real assets including Treasury Inflation-Protected Securities ("TIPS"), commodities, and Master Limited Partnerships ("MLPs"), and 10 percent private real assets. The qualified pension plan assets are invested across global public equity, private equity, cash, core fixed income, long-term core fixed income, investment grade credit, high yield fixed income, emerging markets fixed income, global TIPS, commodities, MLPs, and private real assets. The TVARS asset allocation policy includes permissible deviations from these target allocations. The TVARS Board can take action, as appropriate, to rebalance the system’s assets consistent with the asset allocation policy. At September 30, 2014 and 2013, the asset holdings of the system included the following:
Asset Holdings of TVARS
At September 30
					Plan Assets at September 30
Asset Category		Target Allocation			2014			2013
Global equity		32	%		43	%		48	%
Private equity		10	%		5	%		6	%
Low volatility global public equity		5	%		1	%		—	%
Cash		2	%		2	%		2	%
Core fixed income		5	%		5	%		5	%
Long-term core fixed income		5	%		5	%		4	%
Investment grade credit		6	%		6	%		6	%
International emerging markets fixed income		5	%		5	%		—	%
High yield fixed income		5	%		6	%		10	%
Global TIPS		5	%		5	%		7	%
Private real assets		10	%		7	%		7	%
Commodities		5	%		4	%		—	%
MLPs		5	%		6	%		5	%
Total		100	%		100	%		100	%
Fair Value Measurements
The following table provides the fair value measurement amounts for assets held by TVARS at September 30, 2014:
TVA Retirement System
At September 30, 2014
	Total(1) (2)				Quoted Prices in Active Markets for Identical				Significant Other			Significant
					Assets/Liabilities				Observable Inputs			Unobservable
					(Level 1)				(Level 2)			Inputs
												(Level 3)
Assets
Equity securities	$	1,669			$	1,668			$	—		$	1
Preferred securities	37				5				32			—
Debt securities
Corporate debt securities	1,326				—				1,304			22
Residential mortgage-backed securities	204				—				201			3
Debt securities issued by U.S. Treasury and other U.S. government agencies	93				93				—			—
Debt securities issued by foreign governments	225				—				218			7
Asset-backed securities	176				—				147			29
Debt securities issued by state/local governments	30				—				29			1
Commercial mortgage-backed securities	23				—				20			3
Commingled Funds
Equity	1,106				—				1,106			—
Debt	661				—				661			—
Commodity	332				—				332			—
Blended	228				—				228			—
Institutional mutual funds	28				28				—			—
Cash equivalents and other short-term investments	464				—				464			—
Certificates of deposit	19				—				19			—
Private equity funds	481				—				—			481
Private real estate funds	435				—				334			101
Treasury bills, U.S. Government notes, and securities held as futures and other derivative collateral	35				10				25			—
Securities lending commingled funds	2				—				2			—
Derivatives
Purchased options	18				—				18			—
Foreign currency forward receivable	8				—				8			—
Total Assets	$	7,600			$	1,804			$	5,148		$	648
Liabilities
Derivatives
Futures	11				$	11			$	—		$	—
Foreign currency forward payable	8				—				8			—
Written option obligations	7				—				7			—
Total Liabilities	$	26			$	11			$	15		$	—
Notes
(1) Excludes approximately $65 million in net payables associated with security purchases and sales and various other payables.
(2) Excludes a $2 million payable for collateral on loaned securities in connection with TVARS’s participation in securities lending programs.
The following table provides the fair value measurement amounts for assets held by TVARS at September 30, 2013:
TVA Retirement System
At September 30, 2013
	Total(1) (2)				Quoted Prices in Active Markets for Identical				Significant Other			Significant
					Assets/Liabilities				Observable Inputs			Unobservable
					(Level 1)				(Level 2)			Inputs
												(Level 3)
Assets
Equity securities	$	1,689			$	1,686			$	—		$	3
Preferred securities	22				17				—			5
Debt securities
Corporate debt securities	1,352				—				1,334			18
Residential mortgage-backed securities	355				—				352			3
Debt securities issued by U.S. Treasury and other U.S. government agencies	113				113				—			—
Debt securities issued by foreign governments	31				—				30			1
Asset-backed securities	120				—				110			10
Debt securities issued by state/local governments	36				—				36			—
Commercial mortgage-backed securities	21				—				18			3
Commingled Funds
Equity	1,182				—				1,182			—
Debt	786				—				786			—
Blended	263				—				263			—
Institutional mutual funds	26				26				—			—
Cash equivalents and other short-term investments	395				1				394			—
Private equity funds	528				—				—			528
Private real estate funds	382				—				297			85
Treasury bills, U.S. Government notes, and securities held as futures and other derivative collateral	39				8				31			—
Securities lending commingled funds	3				—				3			—
Derivatives
Foreign currency forward receivable	6				—				6			—
Purchased options	6				—				6			—
Credit default swaps	4				—				4			—
Written option obligations	4				4				—			—
Total Assets	$	7,363			$	1,855			$	4,852		$	656
Liabilities
Derivatives
Foreign currency forward payable	$	6			$	—			$	6		$	—
Credit default swaps	1				—				1			—
Written option obligations	1				—				1			—
Total Liabilities	$	8			$	—			$	8		$	—
Notes
(1) Excludes approximately $131 million in net payables associated with security purchases and sales and various other payables.
(2) Excludes a $3 million payable for collateral on loaned securities in connection with TVARS’s participation in securities lending programs.
The following table provides a reconciliation of beginning and ending balances of pension plan assets measured at fair value on a recurring basis where the determination of fair value includes significant unobservable inputs (Level 3):
Fair Value Measurements Using Significant Unobservable Inputs
	Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Balance at October 1, 2012	$	633
Net realized/unrealized gains (losses)	45
Purchases, sales, issuances, and settlements (net)	(21		)
Transfers in and/or out of Level 3	(1		)
Balance at September 30, 2013	656
Net realized/unrealized gains (losses)	50
Purchases, sales, issuances, and settlements (net)	(53		)
Transfers in and/or out of Level 3	(5		)
Balance at September 30, 2014	$	648
The following descriptions of the valuation methods and assumptions used by the Plan to estimate the fair value of investments apply to investments held directly by the Plan. Third-party pricing vendors provide valuations for investments held by the Plan in most instances, except for commingled, private equity, and private real estate funds which are priced at net asset values established by the investment managers with possible adjustment by management to reflect estimated current fair value. In instances where pricing is determined to be based on unobservable inputs, or where liquidity restrictions exist in the case of funds valued at net asset value, a Level 3 classification has been assigned.
Equities and Preferred Securities. Investment securities, including common stock, mutual funds, and preferred securities listed on either a national or foreign securities exchange or traded in the over-the-counter National Market System, are generally valued each business day at the official closing price (typically the last reported sale price) on the exchange on which the security is primarily traded. If there are no current day sales, the securities are valued at their last quoted bid price. Equities and preferred securities priced by an exchange in an active market are classified as Level 1. Preferred securities classified as Level 2 may have been priced by dealer quote or using assumptions based on observable market data, such as yields on bonds from the same issuer or industry.
Corporate Debt Securities. Most corporate bonds are valued based upon recent bid prices or the average of recent bid and asked prices when available (Level 2 inputs) and, if not available, they are valued through matrix pricing models developed by sources considered by management to be reliable. Matrix pricing, which is a mathematical technique commonly used to price debt securities that are not actively traded, values debt securities without relying exclusively on quoted prices for the specific securities but rather by relying on the securities’ relationship to other benchmark quoted securities (Level 2 inputs).
Residential Mortgage-Backed Securities. Residential mortgage-backed securities consist of collateralized mortgage obligations ("CMOs") and U.S. pass-through security pools related to government-sponsored enterprises ("GSE"). CMO pricing is typically based on either a volatility-driven, multidimensional, single-cash-flow stream model or an option-adjusted spread model. These models incorporate available market data such as trade information, dealer quotes, market color, spreads, bids, and offers. Pricing for GSE securities, including the Federal Home Loan Mortgage Corporation, the Federal National Mortgage Association, and the Government National Mortgage Association, is typically based on quotes from the To Be Announced ("TBA") market, which is highly liquid with multiple electronic platforms that facilitate the execution of trading between investors and broker/dealers. Prices from the TBA market are then compared against other live data feeds as well as input obtained directly from the dealer community. Most residential mortgage-backed securities are considered to be priced using Level 2 inputs because of the nature of their market-data-based pricing models.
U.S. Treasury and Agency Securities. For U.S. Treasury securities, fair values reflect the closing price reported in the active market in which the security is traded (Level 1 inputs). Agency securities are typically priced using evaluated pricing applications and models incorporating U.S. Treasury yield curves. Agency securities are classified as Level 2 because of the nature of their market-data-based pricing models.
Debt Securities Issued by Foreign Governments. These include foreign government bonds and foreign government inflation-linked securities. They are typically priced based on proprietary discounted cash flow models, incorporating option-adjusted spread features as appropriate. Most debt securities issued by foreign governments are classified as Level 2 because of the nature of their market-data-based pricing models.
Asset-Backed Securities. Asset-backed securities are typically priced based on a single cash-flow stream model, which incorporates available market data such as trade information, dealer quotes, market color, spreads, bids, and offers. Because of the market-data-based nature of such pricing models, most asset-backed securities are classified as Level 2.
Debt Securities Issued by State and Local Governments. Most debt securities issued by state and local governments are priced using market-data-based pricing models, and are therefore classified as Level 2. These pricing models incorporate market data such as quotes, trading levels, spread relationships, and yield curves, as applicable.
Commercial Mortgage-Backed Securities. Commercial mortgage-backed securities are typically priced based on a single-cash-flow stream model, which incorporates available market data such as trade information, dealer quotes, market color, spreads, bids, and offers. Because of the market-data-based nature of such pricing models, most commercial mortgage-backed securities are classified as Level 2.
Commingled Funds. The Plan invests in commingled funds, which include collective trusts, unit investment trusts, and similar investment funds that predominantly hold debt and/or equity securities as underlying assets. The Plan’s ownership consists of a pro rata share and not a direct ownership of an underlying investment. These commingled funds are valued at their closing net asset values (or unit value) per share as reported by the managers of the commingled funds and as supported by the unit prices of actual purchases and sale transactions occurring as of or close to the financial statement date (Level 2 inputs). These net asset values may be adjusted by management if it is determined that they do not reflect a current estimate of fair value.
The Plan is invested in equity commingled funds, which can be categorized as either passively managed index funds or actively managed funds. The equity index funds seek to track the performance of a particular index by replicating its capitalization and characteristics. Passive fund benchmark indices include the Russell 1000 index, the S&P 500 index, and the Morgan Stanley Capital International All Country World Index ex-U.S. The actively managed equity funds seek to outperform certain equity benchmarks through a combination of fundamental and technical analysis. Active funds select portfolio positions based upon their research.
The Plan is invested in actively managed debt commingled funds which seek to outperform certain fixed-income benchmarks through fundamental research and analysis. The funds invest in a diversified portfolio of fixed income securities and derivatives of varying maturities. The objective is to achieve a positive relative total return through active credit selection.
The Plan is invested in commingled funds, which invest across multiple asset classes that can be categorized as blended. These funds seek to outperform a passive benchmark through active security selection. The funds invest in securities across equity, fixed income, currency, and commodities. The portfolios employ fundamental, quantitative, and technical analysis.
The Plan is invested in commodity commingled funds, which can be categorized as actively managed funds. The funds seek to outperform certain commodity benchmarks through fundamental research and analysis. The funds invest in a diversified portfolio of commodity securities and derivatives of varying maturities. The objective is to achieve a positive relative return through active security selection.
The Plan’s investments in equity, debt, blended, and commodity commingled funds can generally be redeemed at any time upon notification of the investment managers, with required notice periods varying from same-day to monthly.
Institutional Mutual Funds. Participation units of institutional mutual funds are stated at their quoted redemption values as reported by the investment managers based on their net asset values, which reflect the fair values of the underlying investments. These funds are traded at published net asset values in an active market (Level 1 inputs).
Cash Collateral Held Under Securities Lending Arrangements. Fair value has been determined to approximate the deposit account balances held in cash collateral pools (Level 2 inputs), as no discounts for credit quality or liquidity were determined to be applicable.
Cash Equivalents and Other Short-Term Investments and Certificates of Deposit. Cash equivalents and other short-term investments are highly liquid securities with a maturity of less than three months and 12 months, respectively. These consist primarily of discount securities such as commercial paper, repurchase agreements, U.S. Treasury bills, and certain agency securities. These securities, as well as certificates of deposit, may be priced at cost, which approximates fair value due to the short-term nature of the instruments. Model based pricing which incorporates observable inputs may also be utilized. These securities are classified as Level 2. Active market pricing may be utilized for U.S. Treasury bills, which are classified as Level 1.
Private Equity Funds. Private equity limited partnerships are reported at net asset values provided by the fund managers. These net asset values may be adjusted by management if it is determined that they do not reflect a current estimate of fair value.
The private equity limited partnerships typically make longer-term investments in private companies and seek to obtain financial returns through long-term appreciation based on corporate stewardship, improved operating processes, and financial restructuring, which may involve a merger or acquisition. Significant investment strategies include venture capital; buyout; mezzanine or subordinated debt; restructuring or distressed debt; and special situations. Venture capital partnerships consist of two main groupings. Early-stage venture capital partnerships invest in businesses still in the conceptual stage where products may not be fully developed and where revenues and/or profits may be several years away. Later-stage venture capital partnerships invest in more mature companies in need of growth or expansion capital. Buyout partnerships provide the equity capital for acquisition transactions either from a private seller or the public, which may represent the purchase of the entire company or a refinancing or recapitalization transaction where equity is invested. Mezzanine or subordinated debt partnerships provide the intermediate capital between equity and senior debt in a buyout or refinancing transaction and typically own a security in the company that carries current interest payments as well as a potential equity interest in the company. Restructuring or distressed debt partnerships purchase opportunities generated by overleveraged or poorly managed companies. Special situation partnerships include organizations with a specific industry focus not covered by the other private equity subclasses or unique opportunities that fall outside the regular subclasses.
The private equity funds have no investment withdrawal provisions prior to the termination of the partnership, and as such are classified as Level 3. Partnerships generally continue 10 to 12 years after the inception of the fund. The partnerships are subject to three to four one-year extensions at the discretion of the General Partner. Partnerships can generally be dissolved by an 80 percent vote in interest by all limited partners, with some funds requiring the occurrence of a specific event.
Private Real Estate Investments. The Plan’s ownership in private real estate investments consists of a pro rata share and not a direct ownership of the underlying investments. The fair values of the Plan’s private real estate investments are estimated utilizing net asset values provided by the investment managers. These net asset values may be adjusted by management if it is determined that they do not reflect a current estimate of fair value. The methodologies utilized by the investment managers to calculate their net asset values are summarized as follows:
The Plan is invested in limited partnerships that invest in real estate securities, real estate partnerships, and direct real estate properties. This includes investments in office, multifamily, industrial, and retail investment properties in the U.S. and international markets. The investment strategy focuses on distressed, opportunistic, and value-added opportunities. Partnership investments also include mortgage and/or real estate-related fixed-income instruments and related securities. Investments are diversified by property type and geographic location.
The Plan is invested in a commingled fund that develops, renovates, and re-leases real estate properties to create value. Investments are predominantly in top tier real estate markets that offer deep liquidity. Property types include residential, office, industrial, hotel, retail, and land. Properties are diversified by geographic region within the U.S. domestic market. The Plan is invested in a second commingled fund that invests primarily in core, well-leased, operating real estate properties with a focus on income generation. Investments are diversified by property type with a focus on office, industrial, apartment, and retail. Properties are diversified within the U.S. with an overweight to major market and coastal regions.
Fair value estimates of the underlying investments in these limited partnerships and commingled fund investments are primarily based upon property appraisal reports prepared by independent real estate appraisers within a reasonable amount of time following acquisition of the real estate and no less frequently than annually thereafter. The appraisals are based on one or a combination of three methodologies: cost of reproduction analysis, discounted cash flow analysis, and sales comparison analysis. Pricing for certain investments in mortgage-backed and asset-backed securities is typically based on models that incorporate observable inputs.
The Plan is invested in a private real estate investment trust formed to make direct or indirect investments in commercial timberland properties. Pricing for these types of investments is based on comprehensive appraisals that are conducted shortly after initial purchase of properties and at three-year intervals thereafter. All appraisals are conducted by third-party timberland appraisal firms. Appraisals are based on either a sales comparison analysis or a discounted cash flow analysis.
The fair value hierarchy level classifications for the Plan’s real estate investments are determined based on redemption terms. Investments which cannot be redeemed at the measurement date, but which can be redeemed at a future date, are evaluated based on the length of time until the investment will become redeemable in determining whether the investment should be reported in either Level 2 or Level 3 of the fair value hierarchy. The redemption provisions vary by fund.
Derivatives. The Plan invests in a variety of derivative instruments. The valuation methodologies for these instruments are as follows:
Options. The Plan enters into purchased and written options. Options that are listed on either a national or foreign securities exchange are generally valued each business day at the official closing price (typically the last reported sales price) on the exchange on which the security is primarily traded. These options are classified as Level 1. Options traded over the counter and not on exchanges are priced by third-party vendors and are classified as Level 2.
Foreign currency forwards. The Plan enters into foreign currency forwards. All commitments are marked to market daily at the applicable translation rates, and any resulting unrealized gains or losses are recorded. Foreign currency forwards are priced by third-party vendors and are classified as Level 2. Foreign currency forwards are disclosed on a net position basis.
Futures. The Plan enters into futures. The futures contracts are listed on either a national or foreign securities exchange and generally valued each business day at the official closing price (typically the last reported sales price) on the exchange on which the security is primarily traded. The pricing is performed by third-party vendors. Since futures are priced by an exchange in an active market, they are classified as Level 1.
Swaps. The Plan enters into various types of swaps. Credit default swaps are priced at market using models that consider cash flows, credit curves, recovery rates, and other factors. The pricing is performed by third-party vendors. Interest rate swap contracts are priced at market using forward rates derived from the swap curve, and the pricing is also performed by third-party vendors. Other swaps such as equity index swaps and variance swaps are priced by third-party vendors using market inputs such as spot rates, yield curves, and volatility. The Plan's swaps are generally classified as Level 2 based on the observable nature of their pricing inputs.
The valuation methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while the Plan believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date.
Cash Flows
Estimated Future Benefit Payments.  The following table sets forth the estimated future benefit payments under the benefit plans.
Estimated Future Benefits Payments
At September 30, 2014
					Other Post-Retirement Benefits
	Pension
	Benefits
2015	$	712			$	39
2016	715				40
2017	720				41
2018	724				41
2019	731				41
2020 - 2024	3,759				186
Contributions.  In 2009, TVA made a contribution to TVARS of $1.0 billion for 2010 and as an advance on contributions for 2011 through 2013. In 2011, TVA made an additional discretionary contribution of $270 million to TVARS. In 2013 and 2012, the qualified defined pension plan's assets exceeded market return expectations and no discretionary contributions were made. The minimum contribution for 2014 was $198 million; however, TVA made a $250 million contribution to TVARS. The 2015 minimum contribution is $215 million; however, TVA expects to contribute $275 million to TVARS in 2015. In 2014, TVA made contributions of $6 million to the SERP and $47 million to the other post-retirement benefit plans. TVA expects to contribute $5 million to the SERP and $39 million to the other post-retirement benefit plans in 2015.
Other Post-Employment Benefits
Post-employment benefit cost estimates are revised to properly reflect changes in actuarial assumptions made at the end of each year. TVA utilizes a discount rate determined by reference to the U.S. Treasury Constant Maturities corresponding to calculated average durations of TVA’s future estimated post-employment claims payments. The use of a 2.52 percent discount rate resulted in the recognition of approximately $34 million in expenses in 2014 and an unpaid benefit obligation of about $520 million at September 30, 2014. The 2014 current portion of the obligation is $48 million and is recorded in Accounts payable and accrued liabilities. The 2014 long-term portion of $472 million is recorded in Post-retirement and post-employment benefit obligations. The amounts in the current portion of the obligation represent the total unpaid losses and administrative fees for each year that are due one month following TVA’s fiscal year end.
The use of a 2.64 percent discount rate resulted in the recognition of approximately $(8) million in expenses in 2013 and an unpaid benefit obligation of about $535 million at September 30, 2013. The 2013 current portion of the obligation is $49 million and is recorded in Accounts payable and accrued liabilities. The 2013 long-term portion of $486 million is recorded in Post-retirement and post-employment benefit obligations. TVA utilized discount rates of 1.65 percent in 2012 resulting in expense of $52 million and a $597 million obligation.
The decrease in the unpaid benefit obligation from 2014 to 2013 is due primarily to the demographic experience gains from decreases in loss experiences and fewer claimants. The decrease in the unpaid benefit obligation and expense from 2012 to 2013 is due primarily to the increase in the discount rate from 1.65 percent in 2012 to 2.64 percent in 2013 resulting in a decrease of $45 million.  Decreases in loss experiences and other changes in demographic experiences also decreased the unpaid benefit obligation and expense to a lesser degree.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	Commitments
	At September 30, 2014, the amounts of contractual cash commitments maturing in each of the next five years and beyond are shown below:
	Commitments and Contingencies
	Payments due in the years ending September 30
			2015		2016		2017		2018		2019		Thereafter		Total
	Debt(1)		$	1,628	$	32	$	1,555	$	1,682	$	1,032	$	17,692	$	23,621
	Debt of VIEs		32		33		35		36		38		1,137		1,311
	Membership interests of variable interest entity subject to mandatory redemption		2		2		2		2		2		29		39
	Lease obligations
	Capital		13		13		13		13		12		167		231
	Non-cancelable operating		38		36		34		27		25		63		223
	Purchase obligations
	Power		220		222		232		235		239		3,364		4,512
	Fuel		1,335		862		477		552		492		1,579		5,297
	Other		304		215		202		199		192		1,640		2,752
	Unfunded loan commitments		13		—		—		—		—		—		13
	Payments on other financings		104		104		104		104		96		305		817
	Total		$	3,689	$	1,519	$	2,654	$	2,850	$	2,128	$	25,976	$	38,816
	Note
	(1) Does not include noncash items of foreign currency exchange loss of $44 million and net discount on sale of Bonds of $89 million.
	In addition to the cash requirements, above, TVA has contractual obligations in the form of revenue discounts related to energy prepayments.  See Note 1 — Energy Prepayment Obligations and Discounts on Sales.
	Energy Prepayment Obligations
	Payments due in the years ending September 30
			2015		2016		2017		2018		2019		Thereafter		Total
	Energy Prepayment Obligations		$	100	$	100	$	100	$	100	$	10	$	—	$	410
	Debt. At September 30, 2014, TVA had outstanding discount notes of $596 million and long-term debt (including current maturities) at varying maturities and interest rates of $23.0 billion for total outstanding indebtedness of $23.6 billion. See Note 13.
	Debt of VIEs. At September 30, 2014, TVA had outstanding long-term debt (including current maturities) attributable to its three VIEs of which it is the primary beneficiary of $1.3 billion. See Note 9.
	Membership Interests of VIE Subject to Mandatory Redemption. At September 30, 2014, TVA had outstanding membership interests subject to mandatory redemption (including current portion) of $39 million issued by one of its VIEs of which it is the primary beneficiary. See Note 9.
	Leases.  TVA leases certain property, plant, and equipment under agreements with terms ranging from one to 80 years.  Of the total obligations for TVA’s capital leases, $124 million represents the cost of financing.  TVA’s rental expense for operating leases was $75 million in 2014, $71 million in 2013, and $67 million in 2012.
	Power Purchase Obligations.  TVA has contracted with various independent power producers and LPCs for additional capability to be made available to TVA. Several of these agreements have contractual minimum payments.  In total, these agreements provide 1,621 MW of summer net capability.  The remaining terms of the agreements range up to 18 years.  TVA incurred $293 million, $322 million, and $447 million of expense under power purchase agreements during 2014, 2013, and 2012, respectively.  Certain power purchase obligations are accounted for as capital leases. Costs under TVA’s power purchase agreements not accounted for as capital leases are included in TVA's consolidated statements of operations as purchased power expense and are expensed as incurred.
	Under federal law, TVA is obligated to purchase power from qualifying facilities, cogenerators, and small power producers.  As of September 30, 2014, there was a combined qualifying capacity of 890 MW from six different suppliers, from which TVA purchased power under this law.  TVA’s obligations to purchase power from these qualifying facilities are not included in the Commitments and Contingencies table.
	TVA, along with others, contracted with the Southeastern Power Administration ("SEPA") to obtain power and energy from eight U.S. Army Corps of Engineers hydroelectric facilities on the Cumberland River system.  The agreement with SEPA can be terminated upon three years’ notice, but this notice of termination may not become effective prior to June 30, 2017.  The contract requires SEPA to provide TVA an annual minimum of 1,500 hours of energy for each megawatt of TVA’s 405 MW allocation, and all surplus energy from the Cumberland River system.  TVA’s obligations under its contract with SEPA are not included in the Commitments and Contingencies table.
	Fuel Purchase Obligations.  TVA has approximately $1.6 billion in long-term fuel purchase commitments ranging in terms of up to 6 years primarily for the purchase and transportation of coal.  TVA also has approximately $3.7 billion of long-term commitments ranging in terms of up to 16 years for the purchase of enriched uranium and fabrication of nuclear fuel assemblies.
	Other Obligations.  Other obligations of $2.8 billion consist of contracts at September 30, 2014, for goods and services primarily related to capital projects as well as other major recurring operating costs.
	Contingencies
	Nuclear Insurance.  The Price-Anderson Act provides a layered framework of protection to compensate for losses arising from a nuclear event in the United States.  For the first layer, all of the NRC nuclear plant licensees, including TVA, purchase $375 million of nuclear liability insurance from American Nuclear Insurers for each plant with an operating license.  Funds for the second layer, the Secondary Financial Program, would come from an assessment of up to $127 million from the licensees of each of the 104 NRC licensed reactors in the United States.  The assessment for any nuclear accident would be limited to $19 million per year per unit.  American Nuclear Insurers, under a contract with the NRC, administers the Secondary Financial Program.  With its six licensed units, TVA could be required to pay a maximum of $764 million per nuclear incident, but it would have to pay no more than $114 million per incident in any one year.  When the contributions of the nuclear plant licensees are added to the insurance proceeds of $375 million, over $13.0 billion, including a five percent surcharge for legal expenses, would be available.  Under the Price-Anderson Act, if the first two layers are exhausted, the U.S. Congress is required to take action to provide additional funds to cover the additional losses.
	TVA carries property, decommissioning, and decontamination insurance of $5.1 billion for its licensed nuclear plants, with up to $2.1 billion available for a loss at any one site, to cover the cost of stabilizing or shutting down a reactor after an accident.  Some of this insurance, which is purchased from Nuclear Electric Insurance Limited ("NEIL"), may require the payment of retrospective premiums up to a maximum of approximately $120 million.
	TVA purchases accidental outage (business interruption) insurance for TVA’s nuclear sites from NEIL.  In the event that an accident covered by this policy takes a nuclear unit offline or keeps a nuclear unit offline, NEIL will pay TVA, after a waiting period, an indemnity (a set dollar amount per week) up to a maximum indemnity of $490 million per unit.  This insurance policy may require the payment of retrospective premiums up to a maximum of approximately $35 million.
	Decommissioning Costs.  TVA recognizes legal obligations associated with the future retirement of certain tangible long-lived assets related primarily to coal-fired generating plants and nuclear generating plants, hydroelectric generating plants/dams, transmission structures, and other property-related assets.
	Nuclear.  Provision for decommissioning costs of nuclear generating units is based on options prescribed by the NRC procedures to dismantle and decontaminate the facilities to meet the NRC criteria for license termination.  At September 30, 2014, the present value of the estimated future decommissioning cost of $2.1 billion was included in AROs.  The actual decommissioning costs may vary from the derived estimates because of, among other things, changes in current assumptions, such as the assumed dates of decommissioning, changes in regulatory requirements, changes in technology, and changes in the cost of labor, materials, and equipment.  Utilities that own and operate nuclear plants are required to use different procedures in calculating nuclear decommissioning costs under GAAP than those that are used in calculating nuclear decommissioning costs when reporting to the NRC.  The two sets of procedures produce different estimates for the costs of decommissioning primarily because of the difference in the discount rates used to calculate the present value of decommissioning costs.
	TVA maintains a NDT to provide funding for the ultimate decommissioning of its nuclear power plants.  TVA monitors the value of its NDT and believes that, over the long term and before cessation of nuclear plant operations and commencement of decommissioning activities, adequate funds from investments will be available to support decommissioning.  TVA’s nuclear power units are currently authorized to operate until 2020-2036, depending on the unit.  It may be possible to extend the operating life of some of the units with approval from the NRC.  See Note 8 — Nuclear Decommissioning Costs and Note 12.
	Non-Nuclear Decommissioning.  The present value of the estimated future non-nuclear decommissioning cost ARO was $1.1 billion at September 30, 2014.  This decommissioning cost estimate involves estimating the amount and timing of future expenditures and making judgments concerning whether or not such costs are considered a legal obligation.  Estimating the amount and timing of future expenditures includes, among other things, making projections of the timing and duration of the asset retirement process and how costs will escalate with inflation.  The actual decommissioning costs may vary from the derived estimates because of changes in current assumptions, such as the assumed dates of decommissioning, changes in regulatory requirements, changes in technology, and changes in the cost of labor, materials, and equipment.
	TVA maintains an ART to help fund the ultimate decommissioning of its power assets.  Estimates involved in determining if additional funding will be made to the ART include inflation rate and rate of return projections on the fund investments.  See Note 8 — Non-Nuclear Decommissioning Costs and Note 12.
	Environmental Matters. TVA’s power generation activities, like those across the utility industry and in other industrial sectors, are subject to most federal, state, and local environmental laws and regulations.  Major areas of regulation affecting TVA’s activities include air quality control, water quality control, and management and disposal of solid and hazardous wastes.  In the future, regulations in all of these areas are expected to become more stringent.  Regulations are also expected to apply to new emissions and sources, with a particular emphasis on climate change, renewable generation, and energy efficiency.
	TVA has incurred, and expects to continue to incur, substantial capital and operating and maintenance costs to comply with evolving environmental requirements primarily associated with, but not limited to, the operation of TVA’s coal-fired generating units.  It is virtually certain that environmental requirements placed on the operation of TVA’s coal-fired and other generating units will continue to become more restrictive and potentially apply to new emissions and sources.  Litigation over emissions or discharges from coal-fired generating units is also occurring, including litigation against TVA.  Failure to comply with environmental laws can result in TVA being subject to enforcement actions, which can lead to the imposition of significant civil liability, including fines and penalties, criminal sanctions, and/or the shutting down of non-compliant facilities.
	From the 1970s to 2014, TVA spent approximately $5.9 billion to reduce emissions from its power plants, including $378 million, $197 million, and $55 million in 2014, 2013, and 2012, respectively, on clean air controls.  TVA estimates that compliance with future Clean Air Act ("CAA") requirements (excluding greenhouse gas ("GHG") requirements) could lead to additional costs of $900 million from 2015 to 2025 for additional clean air controls.  There could be additional material costs if reductions of GHGs, including carbon dioxide, are mandated under the CAA or by legislation or regulation, or if future legislative, regulatory, or judicial actions lead to more stringent emission reduction requirements for conventional pollutants.  These costs cannot reasonably be predicted at this time because of the uncertainty of such potential actions.
	Liability for releases and cleanup of hazardous substances is primarily regulated by the federal Comprehensive Environmental Response, Compensation, and Liability Act ("CERCLA"), and other federal and parallel state statutes.  In a manner similar to many other industries and power systems, TVA has generated or used hazardous substances over the years.
	TVA is aware of alleged hazardous-substance releases at certain non-TVA areas in connection with which other potentially responsible parties may seek monetary damages from TVA.  There is information indicating that TVA sent a small amount of equipment to Ward Transformer (“Ward”), a non-TVA site in Raleigh, North Carolina.  The site is contaminated by PCBs from electrical equipment due to Ward’s practice of draining such equipment.  A working group of potentially responsible parties is cleaning up on-site contamination in accordance with an agreement with the EPA.  The cleanup effort has been divided into multiple phases, including on-site and downstream cleanup activities, two phases of soil cleanup, supplemental groundwater remediation, and cleanup of off-site contamination in the downstream drainage basin.  TVA settled its potential liability for the on-site removal action for $300 thousand and has agreed to pay approximately $8 thousand to settle its potential liability in connection with an EPA study of the site.  TVA believes that its liability for the remaining cleanup activities as well as any natural resource damages will be less than $1 million.
	TVA operations at some TVA facilities have resulted in oil spills and other contamination that TVA is addressing.  At September 30, 2014 and 2013, TVA’s estimated liability for cleanup and similar environmental work for those sites for which sufficient information is available to develop a cost estimate (primarily the TVA sites) was approximately $15 million, on a non-discounted basis, and was included in Accounts payable and accrued liabilities and Other long-term liabilities on the Consolidated Balance Sheets.
	Other. TVA is undertaking cost reduction initiatives with the goal of keeping rates low, keeping reliability high, and continuing to fulfill its broader mission of environmental stewardship and economic development. TVA’s current focus is on reducing operating and maintenance costs through further efficiency gains and streamlining the organization. The goal is to reduce TVA’s operating and maintenance costs by $500 million by 2015 as compared to its 2013 budget. As part of these cost reduction initiatives, an organizational restructuring occurred in 2014, which resulted in approximately 2,000 position reductions achieved through attrition, elimination of vacant positions, and employees leaving TVA either voluntarily or involuntarily. Certain employees were eligible for severance payments as a result of these cost reduction initiatives. As of September 30, 2014, TVA had $45 million accrued related to estimated future severance payments. See Note 3.
	Legal Proceedings
	From time to time, TVA is party to or otherwise involved in lawsuits, claims, proceedings, investigations, and other legal matters ("Legal Proceedings") that have arisen in the ordinary course of conducting TVA's activities, as a result of a catastrophic event or otherwise.
	General. At September 30, 2014, TVA had accrued approximately $172 million of probable losses with respect to Legal Proceedings and estimated the range of these losses to be from $172 million to $173 million.  Of the accrued amount, $108 million is included in Other long-term liabilities and $64 million is included in Accounts payable and accrued liabilities.  TVA is currently unable to estimate any amount or any range of amounts of reasonably possible losses, and no assurance can be given that TVA will not be subject to significant additional claims and liabilities.  If actual liabilities significantly exceed the estimates made, TVA's results of operations, liquidity, and financial condition could be materially adversely affected.
	Environmental Agreements. In April 2011, TVA entered into two substantively similar agreements, one with the EPA and the other with Alabama, Kentucky, North Carolina, Tennessee, and three environmental advocacy groups: the Sierra Club, the National Parks Conservation Association, and Our Children's Earth Foundation (collectively, the "Environmental Agreements”). They became effective in June 2011. Under the Environmental Agreements, TVA committed to (1) retire on a phased schedule 18 coal-fired units with a combined summer net dependable capability of 2,200 MW, (2) control, convert, or retire additional coal-fired units with a combined summer net dependable capability of 3,500 MW, (3) comply with annual, declining emission caps for SO2 and NOx, (4) invest $290 million in certain TVA environmental projects, (5) provide $60 million to Alabama, Kentucky, North Carolina, and Tennessee to fund environmental projects, and (6) pay civil penalties of $10 million. In exchange for these commitments, most past claims against TVA based on alleged New Source Review and associated violations were waived and cannot be brought against TVA. Future claims including those for sulfuric acid mist and GHG emissions can still be brought against TVA, and claims for increases in particulates can also be pursued at many of TVA’s coal-fired units. Additionally, the Environmental Agreements do not address compliance with new laws and regulations or the cost associated with such compliance.
	The liabilities related to the Environmental Agreements are included in Accounts payable and accrued liabilities and Other long-term liabilities on the September 30, 2014 Consolidated Balance Sheet. In conjunction with the approval of the Environmental Agreements, the TVA Board determined that it was appropriate to record TVA's liabilities under the Environmental Agreements as regulatory assets, and they are included as such on the September 30, 2014 Consolidated Balance Sheet and will be recovered in rates in future periods.
	Several legal and administrative clean air proceedings have already been terminated in connection with the Environmental Agreements. Additionally, the proceeding discussed below involving the John Sevier CAA permit is expected to be narrowed in scope or terminated since TVA has now retired all four of the John Sevier coal-fired units.
	Legal Proceedings Related to the Kingston Ash Spill.  Seventy-eight lawsuits based on the Kingston ash spill were filed in the United States District Court for the Eastern District of Tennessee.  The plaintiffs - residents, businesses, and property owners in the Kingston area - sought unspecified compensatory and punitive damages for various tort claims, court orders to clean up properties, and other relief.  Fifteen of these lawsuits were dismissed prior to the third quarter of 2014.  On August 4, 2014, the court issued an agreed order that implements a mediated global resolution of pending claims.  Under the order, the 63 pending cases were dismissed with prejudice and TVA agreed to deposit $28 million with the court, which is responsible for disbursing the funds.  The order anticipates that further legal proceedings will be required to resolve the claims of nine of the plaintiffs, and a portion of the $28 million has been set aside under the order to cover the anticipated costs of resolving these claims.
	Civil Penalty and Natural Resource Damages for the Kingston Ash Spill.  In June 2010, TDEC issued a civil penalty order of approximately $12 million to TVA for the Kingston ash spill, citing violations of the Tennessee Solid Waste Disposal Act and the Tennessee Water Quality Control Act.  Of the $12 million, TVA initially paid $10 million, and agreed to undertake environmental projects valued at $2 million as a credit against the remaining penalty amount. TVA completed several of those projects and has now decided to pay TDEC the remaining difference rather than do more projects. TVA has paid TDEC $750 thousand toward the remaining amount and still must pay another small amount.
	Case Involving Tennessee Valley Authority Retirement System.  In March 2010, eight current and former participants in and beneficiaries of TVARS filed suit in the United States District Court for the Middle District of Tennessee against the six then-current members of the TVARS Board.  The lawsuit challenged the TVARS Board's decision to suspend the TVA contribution requirements for 2010 through 2013, and to amend the TVARS Rules and Regulations to (1) reduce the calculation for COLA benefits for CY 2010 through CY 2013, (2) reduce the interest crediting rate for the fixed fund accounts, and (3) increase the eligibility age to receive COLAs from age 55 to 60.  In September 2010, the district court dismissed this action, allowing the plaintiffs to file an amended complaint within 14 days against TVARS and TVA but not the individual directors, which the plaintiffs did shortly thereafter.  The plaintiffs allege, among other things, violations of their constitutional rights (due process, equal protection, and property rights), violations of the Administrative Procedure Act, and breach of statutory duties owed to the plaintiffs.  They seek a declaratory judgment and appropriate relief for the alleged statutory and constitutional violations and breaches of duty.  TVA filed its answer to the amended complaint in December 2010.  In May 2012, the court granted the parties' joint motion to administratively close the case subject to reopening to allow the parties the opportunity to engage in mediation. In July 2013, the court granted the plaintiffs' motion to reopen the lawsuit, and in November 2013, TVA filed a motion for summary judgment. The motion is still pending.
	Case Involving the NRC Waste Confidence Decision on Spent Nuclear Fuel Storage. In June 2012, the U.S. Court of Appeals for the District of Columbia Circuit ("D.C. Circuit") vacated the NRC's updated WCD. The WCD is a generic determination by the NRC that spent nuclear fuel can be safely managed until a permanent off-site repository is established and has been a key component of the NRC licensing activities since 1984. The most recent update provided that the permanent repository would be available when necessary and that spent fuel could be stored for 60 years after a plant's license terminated. The D.C. Circuit vacated this update on the grounds that, among other things, the NRC failed to support it with an adequate National Environmental Policy Act review and the NRC did not evaluate what would happen if the repository was never built.
	In June 2012, multiple intervenor groups submitted a petition to the NRC to (1) hold in abeyance all pending reactor licensing decisions that would depend upon the WCD and (2) establish a process for ensuring that the remanded proceeding complies with the public participation requirements of Section 189a of the Atomic Energy Act.  In August 2012, the NRC issued an order (the "August 2012 NRC Order") preventing the issuance of a final licensing decision in all proceedings affected by the petition, including Watts Bar Unit 2, Sequoyah, and Bellefonte Units 3 and 4.  While resolution of unrelated contentions can proceed, the NRC stated that it will not issue final licensing decisions until it has “appropriately addressed” the D.C. Circuit decision, and all pending contentions concerning the WCD are being held in abeyance pending the NRC's completion of an environmental review and generic rulemaking addressing the shortcomings identified by the D.C. Circuit. In August 2014, the NRC issued a final rule and terminated its suspension of final licensing decisions, dismissed contentions related to the WCD pending before the NRC, and directed the Atomic Safety and Licensing Board ("ASLB") to dismiss contentions related to the WCD that were being held in abeyance.
	The final rule on continued storage of spent nuclear fuel ("Continued Storage Rule") was published in the Federal Register in September 2014. Multiple intervenor groups submitted a petition to the NRC in multiple reactor licensing proceedings to suspend the issuance of final decisions in those proceedings until the NRC generically makes additional findings related to spent fuel disposal or those findings are made in individual licensing proceedings. In addition, in October 2014, attorneys general from New York, Connecticut, and Vermont filed a petition with the D.C. Circuit for review of the Continued Storage Rule. The petitioners asked the court to vacate the rule and related NRC actions and to remand the matter to the NRC for further analysis and the preparation and issuance of an environmental impact statement that complies with NEPA and other applicable laws and regulations.
Administrative Proceeding Regarding Renewal of Operating License for Sequoyah Nuclear Plant.  In May 2013, the Blue Ridge Environmental Defense League ("BREDL"), the Bellefonte Efficiency and Sustainability Team ("BEST"), and Mothers Against Tennessee River Radiation filed a petition with the NRC opposing the renewal of the operating license for Sequoyah Nuclear Plant Units 1 and 2. The petition contains eight specific contentions challenging the adequacy of the license renewal application that TVA submitted to the NRC in January 2013.  TVA filed a response with the ASLB opposing the admission of all eight of the petitioners' contentions. In July 2013, the ASLB concluded that BREDL is the only one of the three petitioners that has standing to intervene in this proceeding. The ASLB also held that seven of the contentions were inadmissible, and held one portion of the remaining contention related to WCD in abeyance pending further direction from the NRC. In September 2014, the ASLB denied BREDL's contention related to the WCD. Following the publication of the Continued Storage Rule, BREDL filed a petition with the NRC seeking suspension of the issuance of a final decision in the Sequoyah Nuclear Plant proceeding and a motion with the ASLB seeking leave to file a new, late-filed contention related to the Continued Storage Rule. See Case Involving the NRC Waste Confidence Decision on Spent Nuclear Fuel Storage.
Administrative Proceedings Regarding Bellefonte Units 3 and 4.  TVA submitted its combined construction and operating license application ("CCOLA") for two Advanced Passive 1000 reactors at Bellefonte Units 3 and 4 to the NRC in October 2007.  In June 2008, BEST, BREDL, and Southern Alliance for Clean Energy ("SACE") submitted a joint petition for intervention and a request for a hearing.  The ASLB denied standing to BEST and admitted four of the 20 contentions submitted by BREDL and SACE.  The NRC reversed the ASLB's decision to admit two of the four contentions, leaving only two contentions (concerning the estimated costs of the new nuclear plant and the impact of the facility's operations on aquatic ecology) to be litigated in a future hearing.  In January 2012, TVA notified the ASLB that the NRC had placed the CCOLA in “suspended” status indefinitely at TVA's request, and TVA requested that the ASLB hold the proceeding in abeyance pending a decision by TVA regarding the best path forward with regards to the CCOLA.
In July 2012, BREDL petitioned for the admission of another new, late-filed contention stemming from the D.C. Circuit's order vacating the WCD. In September 2014, the ASLB denied BREDL’s request to file the new contention. Following the publication of the Continued Storage Rule, BREDL filed a petition with the NRC seeking suspension of the issuance of a final decision in the Bellefonte Units 3 and 4 proceeding and a motion with the ASLB seeking leave to file a new, late-filed contention stemming from the Continued Storage Rule. See Case Involving the NRC Waste Confidence Decision on Spent Nuclear Fuel Storage.
Administrative Proceedings Regarding Watts Bar Unit 2.  In July 2009, SACE, the Tennessee Environmental Council, the Sierra Club, We the People, and BREDL filed a request for a hearing and petition to intervene in the NRC administrative process reviewing TVA's application for an operating license for Watts Bar Unit 2.  In November 2009, the ASLB granted SACE's request for hearing, admitted two of SACE's seven contentions for hearing, and denied the request for hearing submitted on behalf of the other four petitioners.  The ASLB subsequently dismissed one contention, leaving one aquatic impact contention.  In November 2011, TVA filed a motion for summary disposition, arguing that additional aquatic studies conducted by TVA indicate there is no longer a genuine issue of material fact in connection with SACE's remaining aquatic impact contention.  In July 2013, SACE filed a motion to withdraw its aquatic impact contention.  The ASLB has granted this motion.
In July 2012, SACE petitioned for the admission of another new, late-filed contention, similar to the one filed in the Bellefonte Units 3 and 4 proceeding, stemming from the D.C. Circuit's order vacating the WCD. In September 2014, the ASLB denied SACE’s request to file the contention related to the WCD and terminated the proceeding. Following the publication of the Continued Storage Rule, SACE filed a petition with the NRC seeking suspension of the issuance of a final decision in the Watts Bar Unit 2 proceeding and motions with the ASLB to reopen the record and for leave to file a new, late-filed contention stemming from the Continued Storage Rule. See Case Involving the NRC Waste Confidence Decision on Spent Nuclear Fuel Storage.
John Sevier Fossil Plant Clean Air Act Permit. In September 2010, the Environmental Integrity Project, the Southern Environmental Law Center, and the Tennessee Environmental Council filed a petition with the EPA, requesting that the EPA Administrator object to the CAA permit issued to TVA for operation of John Sevier. Among other things, the petitioners allege that repair, maintenance, or replacement activities undertaken at John Sevier Unit 3 in 1986 triggered the Prevention of Significant Deterioration ("PSD") requirements for SO2 and NOx. The CAA permit, issued by TDEC, remains in effect pending the disposition of the petition. The Environmental Agreements should narrow the scope of this proceeding. See Environmental Agreements. TVA has now retired all four John Sevier coal-fired units, and this challenge likely will not proceed.
National Environmental Policy Act Challenge at Gallatin Fossil Plant. To comply with the Environmental Agreements and the Mercury and Air Toxics Standards, TVA chose to reduce emissions at the Gallatin Fossil Plant by installing controls and an associated landfill. Pursuant to the National Environmental Policy Act ("NEPA"), TVA completed an Environmental Assessment in March 2013 to assess the impact of installing these emission controls. In April 2013, the Tennessee Environmental Council, Tennessee Scenic Rivers Association, Sierra Club, and Center for Biological Diversity filed suit in the United States District Court for the Middle District of Tennessee alleging that TVA violated NEPA when it decided to install additional emission controls and construct an associated landfill at the Gallatin Fossil Plant. Plaintiffs demand that TVA prepare an Environmental Impact Statement, and are asking the court to enjoin TVA from taking any further action relating to these matters pending compliance with NEPA. This case was transferred to the United States District Court for the Eastern District of Tennessee, and in August 2014, the court granted TVA's motion for summary judgment and dismissed all of the plaintiffs' claims. The plaintiffs did not appeal the district court’s judgment by the appeal deadline of September 30, 2014.
National Environmental Policy Act Challenge at Paradise Fossil Plant. To comply with EPA’s Mercury and Air Toxics Standards, TVA chose to retire two coal-fired units at Paradise Fossil Plant and replace them with natural gas generation. Prior to making this decision, TVA completed an Environmental Assessment in November 2013 under NEPA. In July 2014, the Kentucky Coal Association and several individuals filed suit in the United States District Court for the Western District of Kentucky alleging that TVA violated NEPA and the Energy Policy Act of 1992 in deciding to switch to natural gas generation. The plaintiffs demand that TVA prepare an Environmental Impact Statement, and are asking the court to preliminarily enjoin TVA from taking any further action relating to these matters pending compliance with NEPA. TVA has filed an opposition to the plaintiffs’ motion for a preliminary injunction as well as a motion for judgment on the administrative record. A hearing on the preliminary injunction motion is scheduled in November 2014, and briefing on TVA’s motion for judgment is ongoing.
Kingston Fossil Plant NPDES Permit Administrative Appeal.  The Sierra Club filed a challenge to the National Pollutant Discharge Elimination System ("NPDES") permit issued by Tennessee for the scrubber-gypsum pond discharge at Kingston in November 2009 before the Tennessee Board of Water Quality, Oil, and Gas ("TN Board").  TDEC is the defendant in the challenge, and TVA has intervened in support of TDEC's decision to issue the permit.  At the request of the parties, the Administrative Law Judge ("ALJ") assigned to the matter has stayed the case until October 15, 2015.
Bull Run Fossil Plant NPDES Permit Administrative Appeal.  SACE and the Tennessee Clean Water Network ("TCWN") filed a challenge to the NPDES permit for the Bull Run Fossil Plant in November 2010.  TDEC is the defendant in the challenge, and TVA's motion to intervene to support TDEC's decision to issue the permit was granted in January 2011.  At the contested case hearing in October 2013, the TN Board granted TDEC's and TVA's joint motion for involuntary dismissal following the conclusion of the petitioners' presentation of evidence. On December 18, 2013, TCWN and SACE filed a petition for review of the TN Board's decision in the Chancery Court for Davidson, County, Tennessee. The parties have filed appellate briefs, and oral argument is set to be heard on January 27, 2015.
Johnsonville Fossil Plant NPDES Permit Administrative Appeal.  SACE and TCWN filed a challenge to the NPDES permit for the Johnsonville Fossil Plant in March 2011.  TDEC is the defendant in the challenge.  TVA's motion to intervene was granted in August 2011. The matter has not yet been given a hearing date before the TN Board.
John Sevier Fossil Plant NPDES Permit Administrative Appeal.  SACE and TCWN filed a challenge to the NPDES permit for John Sevier in May 2011.  TDEC is the defendant in the challenge.  TVA's motion to intervene was granted in August 2011. The matter has not yet been given a hearing date before the TN Board.
Gallatin Fossil Plant NPDES Permit Administrative Appeal. SACE, TCWN, and the Sierra Club filed a challenge to the NPDES permit for the Gallatin Fossil Plant in June 2012. TDEC is the defendant in the challenge. TVA's motion to intervene was granted in September 2012. Following discovery, SACE, TCWN, and the Sierra Club voluntarily dismissed seven of the eight claims asserted in their petition. TVA moved to dismiss the remaining claim, and the ALJ assigned to the matter granted TVA’s motion and dismissed the case. On November 7, 2014, SACE, TWCN, and the Sierra Club filed a petition for review of the ALJ's dismissal in the Chancery court for Davidson County, Tennessee.
Petitions Resulting from Japanese Nuclear Events. As a result of events that occurred at the Fukushima Daiichi Nuclear Power Plant in March 2011, petitions have been filed with the NRC which could impact TVA's nuclear program. While some petitions have been dismissed after review, petitions that remain open include the following:
•	Petition to Immediately Suspend the Operating Licenses of GE BWR Mark I Units Pending the Full NRC Review With Independent Expert and Public Participation From Affected Emergency Planning Zone Communities
Beyond Nuclear filed a petition in April 2011, requesting that the NRC take emergency enforcement action against all nuclear reactor licensees that operate units that use the General Electric Mark I BWR design. TVA uses this design at Browns Ferry Units 1, 2, and 3. The petition requests the NRC to take several actions, including the suspension of the operating licenses at the affected nuclear units, including Browns Ferry, until several milestones have been met. In December 2011, the NRC provided its initial response to the petition. The NRC accepted five specific requests that would apply directly or indirectly to Browns Ferry, including issues relating to spent fuel pool use and location, Mark I containment hardened vent systems and design, and backup electrical power. Each of these items was accepted for further investigation, but the requests for immediate action were rejected. The NRC has not yet rendered a decision regarding the petition.
•	Twelve separate petitions on various issues
In August 2011, the Natural Resources Defense Council submitted twelve separate letters to the NRC requesting action on various health and safety aspects of operating nuclear facilities in the United States. The NRC is treating these as a single 10 CFR 2.206 Petition. The NRC closed this petition on June 17, 2014.
•	Petition Pursuant to 10 CFR 2.206 - Demand For Information Regarding Compliance with 10 CFR 50, Appendix A, General Design Criterion 44, Cooling Water, and 10 CFR 50.49, Environmental Qualification of Electric Equipment Important to Safety for Nuclear Power Plants.
A petition was filed by the Union of Concerned Scientists in July 2011, requesting that a demand for information be issued for affected licensees, including TVA with regards to Browns Ferry, describing how the facilities comply with General Design Criterion 44, Cooling Water, within Appendix A to 10 CFR Part 50, and with 10 CFR 50.49, Environmental Qualification of Electric Equipment Important to Safety for Nuclear Power Plants, for all applicable design and licensing bases events. The NRC has not yet rendered a decision regarding the petition.

Related_Parties

Related Parties	12 Months Ended
	Sep. 30, 2014
Related Party Transactions [Abstract]	'
Related Parties	'
	Related Parties
	TVA is a wholly-owned corporate agency of the federal government, and because of this relationship, TVA’s revenues and expenses are included as part of the federal budget as a revolving fund.  TVA’s purpose and responsibilities as an agency are described under the “Other Agencies” section of the federal budget.
	TVA currently receives no appropriations from Congress and funds its business using power system revenues, power financings, and other revenues.  TVA is a source of cash to the federal government.  With its payment of $10 million during 2014, TVA fulfilled its requirement to repay $1.0 billion of its Power Program Appropriation Investment. TVA will continue to pay a return on the outstanding balance of this investment indefinitely.  See Note 17 — Appropriation Investment.
	TVA also has access to a financing arrangement with the U.S. Treasury pursuant to the TVA Act.  TVA and the U.S. Treasury entered into a memorandum of understanding under which the U.S. Treasury provides TVA with a $150 million credit facility.  This credit facility was renewed and has a maturity date of September 30, 2015.  Access to this credit facility or other similar financing arrangements has been available to TVA since the 1960s.  See Note 13 — Credit Facility Agreements.
	In the normal course of business, TVA contracts with other federal agencies for sales of electricity and other services.  Transactions with agencies of the federal government were as follows:
	Related Party Transactions
	For the years ended, or at, September 30
		2014		2013		2012
	Revenue from sales of electricity	$	128	$	120	$	117
	Other income	137		102		164
	Operating and maintenance	286		314		375
	Cash and cash equivalents	35		38		32
	Accounts receivable, net	85		58		49
	Accounts payable and accrued liabilities	146		133		204
	Long-term power bonds, net	3		—		—
	Return on Power Program Appropriation Investment	4		7		7
	Return of Power Program Appropriation Investment	10		20		20

Unaudited_Quarterly_Financial_

Unaudited Quarterly Financial Information	12 Months Ended
	Sep. 30, 2014
Quarterly Financial Information Disclosure [Abstract]	'
Unaudited Quarterly Financial Information	'
	Unaudited Quarterly Financial Information
	A summary of the unaudited quarterly results of operations for the years 2014 and 2013 follows.  This summary should be read in conjunction with the audited consolidated financial statements appearing herein.  Results for interim periods may fluctuate as a result of seasonal weather conditions, changes in rates, and other factors.
	Unaudited Quarterly Financial Information
	2014
		First			Second		Third			Fourth		Total
	Operating revenues	$	2,382		$	2,938	$	2,651		$	3,166	$	11,137
	Operating expenses	2,164			2,362		2,453			2,569		9,548
	Operating income	218			576		198			597		1,589
	Net income (loss)	(67		)	295		(81		)	322		469
	Unaudited Quarterly Financial Information
	2013
		First			Second		Third			Fourth		Total
	Operating revenues	$	2,579		$	2,741	$	2,602		$	3,034	$	10,956
	Operating expenses	2,523			2,380		2,324			2,276		9,503
	Operating income	56			361		278			758		1,453
	Net income (loss)	(245		)	54		(12		)	474		271

Summary_of_Significant_Account1

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
General	'
	General
	The Tennessee Valley Authority ("TVA") is a corporate agency and instrumentality of the United States that was created in 1933 by legislation enacted by the United States ("U.S.") Congress in response to a request by President Franklin D. Roosevelt.  TVA was created to, among other things, improve navigation on the Tennessee River, reduce the damage from destructive flood waters within the Tennessee River system and downstream on the lower Ohio and Mississippi Rivers, further the economic development of TVA's service area in the southeastern United States, and sell the electricity generated at the facilities TVA operates.
	Today, TVA operates the nation's largest public power system and supplies power in most of Tennessee, northern Alabama, northeastern Mississippi, and southwestern Kentucky and in portions of northern Georgia, western North Carolina, and southwestern Virginia to a population of over nine million people.
	TVA also manages the Tennessee River, its tributaries, and certain shorelines to provide, among other things, year-round navigation, flood damage reduction, and affordable and reliable electricity. Consistent with these primary purposes, TVA also manages the river system and public lands to provide recreational opportunities, adequate water supply, improved water quality, cultural and natural resource protection, and economic development.
	The power program has historically been separate and distinct from the stewardship programs.  It is required to be self-supporting from power revenues and proceeds from power financings, such as proceeds from the issuance of bonds, notes, or other evidences of indebtedness ("Bonds").  Although TVA does not currently receive congressional appropriations, it is required to make annual payments to the U.S. Treasury as a return on the government's appropriation investment in TVA's power facilities (the "Power Program Appropriation Investment").  In the 1998 Energy and Water Development Appropriations Act, Congress directed TVA to fund essential stewardship activities related to its management of the Tennessee River system and nonpower or stewardship properties with power revenues in the event that there were insufficient appropriations or other available funds to pay for such activities in any fiscal year.  Congress has not provided any appropriations to TVA to fund such activities since 1999.  Consequently, during 2000, TVA began paying for essential stewardship activities primarily with power revenues, with the remainder funded with user fees and other forms of revenues derived in connection with those activities.  The activities related to stewardship properties do not meet the criteria of an operating segment under accounting principles generally accepted in the United States of America ("GAAP").  Accordingly, these assets and properties are included as part of the power program, TVA's only operating segment.
	Power rates are established by the TVA Board of Directors ("TVA Board") as authorized by the Tennessee Valley Authority Act of 1933, as amended, 16 U.S.C. §§ 831-831ee (as amended, the “TVA Act”).  The TVA Act requires TVA to charge rates for power that will produce gross revenues sufficient to provide funds for operation, maintenance, and administration of its power system; payments to states and counties in lieu of taxes ("tax equivalents"); debt service on outstanding indebtedness; payments to the U.S. Treasury in repayment of and as a return on the Power Program Appropriation Investment; and such additional margin as the TVA Board may consider desirable for investment in power system assets, retirement of outstanding Bonds in advance of maturity, additional reduction of the Power Program Appropriation Investment, and other purposes connected with TVA's power business.  In setting TVA's rates, the TVA Board is charged by the TVA Act to have due regard for the primary objectives of the TVA Act, including the objective that power shall be sold at rates as low as are feasible.  Rates set by the TVA Board are not subject to review or approval by any state or other federal regulatory body.
Fiscal Year	'
	Fiscal Year
	TVA's fiscal year ends September 30.  Years (2014, 2013, etc.) refer to TVA's fiscal years unless they are preceded by “CY,” in which case the references are to calendar years.
Cost-Based Regulation	'
	Cost-Based Regulation
	Since the TVA Board is authorized by the TVA Act to set rates for power sold to its customers, TVA is self-regulated.  Additionally, TVA's regulated rates are designed to recover its costs.  In view of demand for electricity and the level of competition, TVA believes that rates, set at levels that will recover TVA's costs, can be charged and collected.  As a result of these factors, TVA records certain assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for non-regulated entities.  Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates.  Regulatory liabilities generally represent obligations to make refunds to customers for previous collections for costs that are not likely to be incurred or deferral of gains that will be credited to customers in future periods.  TVA assesses whether the regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, potential legislation, and changes in technology.  Based on these assessments, TVA believes the existing regulatory assets are probable of recovery.  This determination reflects the current regulatory and political environment and is subject to change in the future.  If future recovery of regulatory assets ceases to be probable, or any of the other factors described above cease to be applicable, TVA would no longer be considered to be a regulated entity and would be required to write off these costs.  All regulatory asset write offs would be required to be recognized in earnings in the period in which future recovery ceases to be probable.
Basis of Presentation	'
	Basis of Presentation
	The accompanying consolidated financial statements, which have been prepared in accordance with GAAP, include the accounts of TVA and variable interest entities of which TVA is determined to be the primary beneficiary. See Note 9. Intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements requires TVA to estimate the effects of various matters that are inherently uncertain as of the date of the consolidated financial statements.  Although the consolidated financial statements are prepared in conformity with GAAP, TVA is required to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the amounts of revenues and expenses reported during the reporting period.  Each of these estimates varies in regard to the level of judgment involved and its potential impact on TVA's financial results.  Estimates are considered critical either when a different estimate could have reasonably been used, or where changes in the estimate are reasonably likely to occur from period to period, and such use or change would materially impact TVA's financial condition, results of operations, or cash flows.
Reclassifications	'
	Reclassifications
Cash and Cash Equivalents and Restricted Cash and Investments	'
	Cash and Cash Equivalents
	Cash includes cash on hand and non-interest bearing cash and deposit accounts. All highly liquid investments with original maturities of three months or less are considered cash equivalents.
	Restricted Cash and Investments
	Restricted cash and investments reflect amounts related to collateral posted with TVA by a swap counterparty.
Allowance for Uncollectible Accounts	'
	Allowance for Uncollectible Accounts
	The allowance for uncollectible accounts reflects TVA's estimate of probable losses inherent in its accounts and loans receivable balances.  TVA determines the allowance based on known accounts, historical experience, and other currently available information including events such as customer bankruptcy and/or a customer failing to fulfill payment arrangements after 90 days.  It also reflects TVA's corporate credit department's assessment of the financial condition of customers and the credit quality of the receivables.
	The allowance for uncollectible accounts was $1 million at September 30, 2014, and 2013, for accounts receivable.  Additionally, loans receivable of $92 million and $73 million at September 30, 2014, and 2013, respectively, were included in Accounts receivable, net and Other long-term assets and reported net of allowances for uncollectible accounts of $9 million and $10 million at September 30, 2014, and 2013, respectively.
Revenues	'
	Energy Prepayment Obligations and Discounts on Sales
	During 2002, TVA introduced an energy prepayment program, the discounted energy units ("DEU") program.  Under this program, TVA LPCs could purchase DEUs generally in $1 million increments, and each DEU entitles the purchaser to a $.025/kilowatt-hour discount on a specified quantity of firm power over a period of years (5, 10, 15, or 20) for each kilowatt-hour in the prepaid block.  The remainder of the price of the kilowatt-hours delivered to the LPC is due upon billing.  TVA’s DEU program allowed LPCs to use cash on hand to prepay TVA for some of their power needs, providing funding to TVA and a savings to LPCs in the form of a discount on future purchases.  The LPC receives a discount on a specified volume of firm energy purchased.  The supplement to the power contract specifies the discount rate (2.5 cents per kilowatt-hour), the monthly block of kilowatt-hours to which the discount applies, the number of years (term), and contingencies upon contract termination.
	TVA has not offered the DEU program since the end of 2004.  Total sales for the program since inception have been approximately $55 million.  TVA accounted for the prepayment proceeds as unearned revenue and reported the obligations to deliver power as Energy prepayment obligations and Current portion of energy prepayment obligations on the September 30, 2013 Consolidated Balance Sheet. There were no outstanding DEU liabilities at September 30, 2014.
	TVA recognizes revenue as electricity is delivered to LPCs, based on the ratio of units of kilowatt-hours delivered to total units of kilowatt-hours under contract.  At September 30, 2014, all of TVA’s obligations under the DEU program had expired, and the entire approximately $55 million had been applied against power billings on a cumulative basis during the life of the program, of which less than $1 million was recognized as noncash revenue during 2014.  Approximately $2 million and $5 million were applied against power billings during 2013 and 2012, respectively.
	In 2004, TVA and its largest customer, Memphis Light, Gas and Water Division ("MLGW"), entered into an energy prepayment agreement under which MLGW prepaid TVA $1.5 billion for the future costs of electricity to be delivered by TVA to MLGW over a period of 180 months.  TVA accounted for the prepayment as unearned revenue and is reporting the obligation to deliver power under this arrangement as Energy prepayment obligations and Current portion of energy prepayment obligations on the September 30, 2014 and 2013 Consolidated Balance Sheets.  TVA expects to recognize approximately $100 million of noncash revenue in each year of the arrangement as electricity is delivered to MLGW based on the ratio of units of kilowatt-hours delivered to total units of kilowatt-hours under contract.  At September 30, 2014, approximately $1.1 billion had been recognized as noncash revenue on a cumulative basis during the life of the agreement, $100 million of which was recognized as noncash revenue during each of 2014, 2013, and 2012.
	Discounts, which are recorded as a reduction to electricity sales, for both programs amounted to $46 million for the year ended September 30, 2014, and $47 million for each of the years ended September 30, 2013, and 2012.
	Revenues
	Revenues from power sales are recorded as electricity is delivered to customers. In addition to power sales invoiced and recorded during the month, TVA accrues estimated unbilled revenues for power sales provided to six customers whose billing date occurs prior to the end of the month.  Exchange power sales are presented in the accompanying consolidated statements of operations as a component of Sales of electricity. Exchange power sales are sales of excess power after meeting TVA native load and directly served requirements.  (Native load refers to the customers on whose behalf a company, by statute, franchise, regulatory requirement, or contract, has undertaken an obligation to serve.)
	From time to time TVA transfers fiber optic capacity on TVA’s network to telecommunications service carriers and local power company customers of TVA ("LPCs").  These transactions are structured as indefeasible rights of use ("IRUs"), which are the exclusive right to use a specified amount of fiber optic capacity for a specified term.  TVA accounts for the consideration received on transfers of fiber optic capacity for cash and on all of the other elements deliverable under an IRU as revenue ratably over the term of the agreement.  TVA does not recognize revenue on any contemporaneous exchanges of its fiber optic capacity for an IRU of fiber optic capacity of the counterparty to the exchange.
	TVA engages in a wide array of arrangements in addition to power sales.  TVA records revenue when it is realized or realizable and earned when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the price or fee is fixed or determinable; and collectability is reasonably assured. Revenues from activities related to TVA’s overall mission are recorded as other operating revenue versus those that are not related to the overall mission, which are recorded in Other income (expense), net.
Inventories	'
	Inventories
	Certain Fuel, Materials, and Supplies.  Coal, oil, limestone, tire-based fuel inventories, and materials and supplies inventories are valued using an average unit cost method.  A new average cost is computed after each inventory purchase transaction, and inventory issuances are priced at the latest moving weighted average unit cost. Natural gas inventories are valued using an average cost method, and a new average cost is computed monthly.
	Allowance for Inventory Obsolescence.  TVA reviews material and supplies inventories by category and usage on a periodic basis.  Each category is assigned a probability of becoming obsolete based on the type of material and historical usage data.  Based on the estimated value of the inventory, TVA adjusts its allowance for inventory obsolescence.
	Emission Allowances.  TVA has emission allowances for sulfur dioxide ("SO2") and nitrogen oxides ("NOx") which are accounted for as inventory.  The average cost of allowances used each month is charged to operating expense based on tons of SO2 and NOx emitted during the respective compliance periods.  Allowances granted to TVA by the Environmental Protection Agency ("EPA") are recorded at zero cost.
Property, Plant, and Equipment, and Depreciation	'
	Property, Plant, and Equipment, and Depreciation
	Property, Plant, and Equipment. Additions to plant are recorded at cost, which includes direct and indirect costs and an allowance for funds used during construction ("AFUDC").  The cost of current repairs and minor replacements is charged to operating expense.  Nuclear fuel inventories, which are included in Property, plant, and equipment, are valued using the average cost method for raw materials and the specific identification method for nuclear fuel in a reactor.  Amortization of nuclear fuel in a reactor is calculated on a units-of-production basis and is included in fuel expense.
	Depreciation. TVA accounts for depreciation of its properties using the composite depreciation convention of accounting.  Accordingly, the original cost of property retired is charged to accumulated depreciation. Except as described below, depreciation is generally computed on a straight-line basis over the estimated service lives of the various classes of assets. Depreciation expense for the years ended September 30, 2014, 2013, and 2012 was $1.6 billion, $1.4 billion, and $1.7 billion, respectively. Depreciation expense expressed as a percentage of the average annual depreciable completed plant was 3.42 percent for 2014, 3.12 percent for 2013, and 3.78 percent for 2012.  Average depreciation rates by asset class are as follows:
	Property, Plant, and Equipment Depreciation Rates
	At September 30
	(percent)
		2014	2013	2012
	Asset Class
	Nuclear	2.9	2.86	2.71
	Coal-Fired	4.37	3.47	5.65
	Hydroelectric	1.44	1.3	1.35
	Gas and oil-fired	3.23	3.21	3.67
	Transmission	2.76	2.76	2.99
	Other	8.4	8.14	8.1
	In April 2011, TVA entered into two substantively similar agreements, one with the EPA and the other with Alabama, Kentucky, North Carolina, Tennessee, and three environmental advocacy groups (collectively, the "Environmental Agreements”).  See Note 21 — Legal Proceedings — Environmental Agreements.  Under the Environmental Agreements, TVA committed, among other things, to retire, on a phased schedule, 18 coal-fired units.
	Consistent with the Environmental Agreements, Units 1 and 2 at John Sevier Fossil Plant ("John Sevier") were retired
	on December 31, 2012, and Units 3 and 4 were idled on December 31, 2012 and subsequently retired on June 25, 2014. Units 3 and 5 at Widows Creek Fossil Plant ("Widows Creek") were retired on July 31, 2013, and Units 1, 2, 4, and 6 at Widows Creek were retired on July 31, 2014. On October 1, 2013, Colbert Fossil Plant ("Colbert") Unit 5 and Johnsonville Fossil Plant ("Johnsonville") Units 5, 6, 9, and 10 were idled. In addition, Units 7 and 8 at Johnsonville were idled March 1, 2012, and Unit 10 at Shawnee Fossil Plant ("Shawnee") was idled in October 2010 and subsequently retired on June 30, 2014.
	On November 14, 2013, the TVA Board of Directors (the "TVA Board") approved the retirement of Colbert Units 1-5 no later than June 30, 2016, and the retirement of Widows Creek Unit 8. Additionally, the TVA Board approved the retirement of Paradise Fossil Plant ("Paradise") Units 1 and 2 upon the completion of a natural gas-fired plant at the Paradise location.
	On August 21, 2014, the TVA Board approved the retirement of Allen Fossil Plant ("Allen") Units 1-3 upon the completion of a natural gas-fired plant at the Allen location.
	Depreciation rates are adjusted to reflect current assumptions so that the units will be fully depreciated by the applicable idle dates.  As a result of TVA's decision to idle or retire units, TVA recognized $206 million and $49 million in accelerated depreciation expense related to the units during the years ended September 30, 2014, and 2013, respectively.
	Capital Lease Agreements.  Property, plant, and equipment also includes assets recorded under capital lease agreements. These primarily consist of a natural gas lateral pipeline, power production facilities, water treatment assets, and land of $102 million and $42 million at September 30, 2014 and 2013, respectively, and fuel fabrication and blending facilities of $5 million at September 30, 2013. There were no obligations for fuel fabrication and blending facilities at September 30, 2014. Amortization expense related to capital leases is included in Depreciation and amortization in TVA’s statements of operations.
	Allowance for Funds Used During Construction.  AFUDC capitalized during the year ended September 30, 2014, was $175 million, as compared to $168 million capitalized during the year ended September 30, 2013.  TVA capitalizes interest as AFUDC, based on the average interest rate of TVA’s outstanding debt.  The allowance is applicable to construction in progress related to projects with (1) an expected total project cost of $1.0 billion or more, and (2) an estimated construction period of at least three years in duration. During 2012 and 2011, TVA also included certain nuclear fuel inventories in the calculation of the allowance. During 2012, the TVA Board approved a change in the AFUDC methodology which removed the inclusion of nuclear fuel from the AFUDC calculation effective October 1, 2012. The accumulated balance of costs, which is used to calculate AFUDC, averaged approximately $3.3 billion for the year ended September 30, 2014. Subsequent to August 31, 2013, the accumulated balance of costs for Bellefonte Nuclear Plant ("Bellefonte") were removed from this calculation.
	Software Costs.  TVA capitalizes certain costs incurred in connection with developing or obtaining internal-use software. Capitalized software costs are included in Property, plant, and equipment on the consolidated balance sheets and are amortized primarily over five years.  At September 30, 2014 and 2013, unamortized computer software costs totaled $22 million and $5 million, respectively.  Amortization expense related to capitalized computer software costs was $31 million for each of 2014, 2013, and 2012.  Software costs that do not meet capitalization criteria are expensed as incurred.
	Impairment of Assets.  TVA evaluates long-lived assets for impairment when events or changes in circumstances indicate that the carrying value of such assets may not be recoverable.  For long-lived assets, TVA bases its evaluation on impairment indicators such as the nature of the assets, the future economic benefit of the assets, any historical or future profitability measurements, and other external market conditions or factors that may be present.  If such impairment indicators are present or other factors exist that indicate that the carrying amount of an asset may not be recoverable, TVA determines whether an impairment has occurred based on an estimate of undiscounted cash flows attributable to the asset as compared with the carrying value of the asset.  If an impairment has occurred, the amount of the impairment recognized is measured as the excess of the asset’s carrying value over its fair value.  Additionally, TVA regularly evaluates construction projects.  If the project is canceled or deemed to have no future economic benefit, the project is written off as an asset impairment or, upon Board approval, reclassified as a regulatory asset.
Decommissioning Costs	'
	Decommissioning Costs
	TVA recognizes legal obligations associated with the future retirement of certain tangible long-lived assets.  These obligations relate to fossil fuel-fired generating plants, nuclear generating plants, hydroelectric generating plants/dams, transmission structures, and other property-related assets.  These other property-related assets include, but are not limited to, easements and coal rights.  Activities involved with retiring these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site reclamation.  Revisions to the estimates of asset retirement obligations ("AROs") are made whenever factors indicate that the timing or amounts of estimated cash flows have changed.  Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset.  See Note 8 — Nuclear Decommissioning Costs and Non-Nuclear Decommissioning Costs and Note 12.
	To estimate its decommissioning obligation related to its nuclear generating stations, TVA uses a probability-weighted, discounted cash flow model which, on a unit-by-unit basis, considers multiple outcome scenarios that include significant estimations and assumptions. Those assumptions include (1) estimates of the cost of decommissioning, (2) the method of decommissioning and the timing of the related cash flows, (3) the license period of the nuclear plant, considering the probability of license extensions, (4) cost escalation factors, and (5) the credit adjusted risk free rate to measure the obligation at the present value of the future estimated costs. Prior to June 30, 2014, TVA based its decommissioning cost estimates on cost elements prescribed by the NRC to dismantle and decommission the radioactive portion of each site with the assumption that decommissioning would occur within the first seven years after plant shut down, which approximates the DECON method of decommissioning. The DECON method requires that radioactive contamination is removed from a site and safely disposed of or decontaminated to a level that permits the site to be released for unrestricted use shortly after it ceases operation. On June 30, 2014, TVA recorded a change in estimate based on site-specific decommissioning cost studies. Additionally, TVA determined it appropriate to reflect an increase in the probability that certain of its nuclear operating licenses will be extended and that there is a probability that it will be able to delay ultimate decommissioning activities under a SAFSTOR method of decommissioning. The SAFSTOR method allows nuclear facilities to be placed and maintained in a condition that allows the facilities to be safely stored and subsequently decontaminated to levels that permit release for unrestricted use. As such, TVA ascribed probabilities to both the SAFSTOR and DECON methods of decommissioning in order to estimate its decommissioning obligation. Decommissioning cost studies will be updated for each of TVA’s nuclear units at least every five years.
Blended Low-Enriched Uranium Program	'
	Blended Low-Enriched Uranium Program
	Under the blended low-enriched uranium ("BLEU") program, TVA, the Department of Energy ("DOE"), and certain nuclear fuel contractors have entered into agreements providing for the DOE's surplus of enriched uranium to be blended with other uranium down to a level that allows the blended uranium to be fabricated into fuel that can be used in nuclear power plants.  This blended nuclear fuel was first loaded in a Browns Ferry Nuclear Plant ("Browns Ferry") reactor in 2005 and is expected to continue to be used to reload the Browns Ferry reactors through at least 2016. BLEU fuel was loaded into Sequoyah Nuclear Plant ("Sequoyah") Unit 2 three times but is not expected to be used in the Sequoyah reactors in the future.
	Under the terms of an interagency agreement between TVA and the DOE, in exchange for supplying highly enriched uranium materials to the appropriate third-party fuel processors for processing into usable BLEU fuel for TVA, the DOE participates to a degree in the savings generated by TVA’s use of this blended nuclear fuel.  The third-party fuel processors own the conversion and processing facilities and will retain title to all land, property, plant, and equipment used in the BLEU fuel program.  Over the life of the program, TVA projects that the DOE’s share of savings generated by TVA’s use of this blended nuclear fuel could result in payments to the DOE of as much as $160 million.  TVA accrues an obligation with each BLEU reload batch related to the portion of the ultimate future payments estimated to be attributable to the BLEU fuel currently in use.  During 2009, the DOE and TVA agreed that this obligation would be offset by amounts that the DOE expects to owe TVA in the future for certain decommissioning costs that TVA will pay on the DOE’s behalf.  Accordingly, TVA will remit the BLEU fuel savings amounts to the DOE, only after those future decommissioning costs have been offset against TVA’s obligation to the DOE. At September 30, 2014, TVA had paid out approximately $101 million for this program, and the obligation recorded was $16 million.
Investment Funds	'
	Investment Funds
	Investment funds consist primarily of trust funds designated to fund nuclear decommissioning requirements (see Note 21 — Contingencies — Decommissioning Costs), non-nuclear AROs (see Note 8 — Non-Nuclear Decommissioning Costs), the Supplemental Executive Retirement Plan ("SERP") (see Note 20 — Overview of Plans and Benefits — Supplemental Executive Retirement Plan), and the Long-Term Deferred Compensation Plan ("LTDCP"). Nuclear decommissioning funds and SERP funds are invested in portfolios of securities generally designed to achieve a return in line with overall equity market performance, while asset retirement and LTDCP funds are invested in portfolios of securities generally designed to achieve a return in line with overall equity and debt market performance. The nuclear decommissioning funds, asset retirement funds, SERP funds, and LTDCP funds are all classified as trading.
Insurance	'
	Insurance
	Although TVA uses private companies to administer its healthcare plans for eligible active and retired employees not covered by Medicare, TVA does not purchase health insurance.  Third-party actuarial specialists assist TVA in determining certain liabilities for self-insured claims.  TVA recovers the costs of claims through power rates and through adjustments to the participants’ contributions to their benefit plans.  These liabilities are included in Other liabilities on the balance sheets.
	The Federal Employees' Compensation Act ("FECA") governs liability to employees for service-connected injuries.  TVA purchases excess workers' compensation insurance above a self-insured retention.
	TVA sponsors an Owner Controlled Insurance Program which provides workers' compensation and liability insurance for a select group of contractors performing maintenance, modifications, outage, and new construction activities at TVA facilities.
	TVA purchases nuclear liability insurance, nuclear property, decommissioning, and decontamination insurance, and nuclear accidental outage insurance.  See Note 21 — Contingencies — Nuclear Insurance.
	TVA purchases excess liability insurance for aviation, auto, marine, and general liability exposures.  TVA purchases property insurance for certain conventional (non-nuclear) assets.
	The insurance policies are subject to the terms and conditions of the specific policy.  Each of the insurance policies purchased contains deductibles or self-insured retentions.  TVA recovers the costs of losses through power rates.
Research and Development Costs	'
	Research and Development Costs
	Research and development costs are expensed when incurred.  TVA’s research programs include those related to power delivery technologies, emerging technologies (clean energy, renewables, distributed resources, and energy efficiency), technologies related to generation (fossil fuel, nuclear, and hydroelectric), and environmental technologies.
Tax Equivalents	'
	Tax Equivalents
	The TVA Act requires TVA to make payments to states and counties in which TVA conducts its power operations and in which TVA has acquired power properties previously subject to state and local taxation.  The total amount of these payments is five percent of gross revenues from sales of power during the preceding year, excluding sales or deliveries to other federal agencies and off-system sales with other utilities, with a provision for minimum payments under certain circumstances. TVA calculates tax equivalent expense by subtracting the prior year fuel cost-related tax equivalent regulatory asset or liability from the payments made to the states and counties and then adds back the current year fuel cost-related tax equivalent regulatory asset or liability. Fuel cost-related tax equivalent expense is recognized in the same accounting period in which the fuel cost-related revenue is recognized.
Maintenance Costs	'
	Maintenance Costs
	TVA records maintenance costs and repairs related to its property, plant, and equipment in the statements of operations as they are incurred except for the recording of certain regulatory assets for retirement and removal costs.

Variable_Interest_Entities_Var

Variable Interest Entities Variable Interest Entities (Policies)	12 Months Ended
	Sep. 30, 2014
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]	'
Variable Interest Entity Policy	'
	Variable Interest Entities
	A VIE is an entity that either (1) has insufficient equity to permit the entity to finance its activities without additional subordinated financial support or (2) has equity investors who lack the characteristics of owning a controlling financial interest. The analysis to determine whether an entity is a VIE considers factors such as contracts with an entity, credit support for an entity, the adequacy of the equity investment of an entity, the extent of an entity's activities that either involve or are conducted on behalf of an investor with disproportionate voting rights, and the relationship of voting power to the amount of equity invested in an entity. A VIE is consolidated by its primary beneficiary. The primary beneficiary has both (i) the power to direct the activities that most significantly impact the entity's economic performance and (ii) the obligation to absorb losses or the right to receive benefits from the entity that could potentially be significant to the VIE. The determination of the primary beneficiary requires continual reassessment.
	When TVA determines that it has a variable interest in a variable interest entity, a qualitative evaluation is performed to assess which interest holders have the power to direct the activities that most significantly impact the economic performance of the entity and have the obligation to absorb losses or receive benefits that could be significant to the entity. The evaluation considers the purpose and design of the business, the risks that the business was designed to create and pass along to other entities, the activities of the business that can be directed and which party can direct them, and the expected relative impact of those activities on the economic performance of the business through its life. TVA has the power to direct the activities of an entity when it has the ability to make key operating and financing decisions, including, but not limited to, capital investment and the issuance of debt.
	Southaven
	On August 9, 2013, TVA entered into a lease financing arrangement with Southaven Combined Cycle Generation, LLC ("SCCG") for the lease by TVA of the Southaven Combined Cycle Facility ("Southaven CCF"). SCCG is a special single-purpose limited liability company formed in June 2013 to finance the Southaven CCF through a $360 million secured notes issuance (the “SCCG notes”) and the issuance of $40 million of membership interests subject to mandatory redemption. The membership interests were purchased by Seven States Southaven, LLC ("SSSL"). SHLLC is a special single-purpose entity, also formed in June 2013, established to acquire and hold the membership interests of SCCG. A non-controlling interest in SHLLC is held by a third party through nominal membership interests, to which none of the income, expenses, and cash flows of SHLLC are allocated.
	The membership interests held by SHLLC were purchased with proceeds from the issuance of $40 million of secured notes (the “SHLLC notes”) and are subject to mandatory redemption pursuant to scheduled amortizing, semi-annual payments due each August 15 and February 15, with a final payment due on August 15, 2033. The payment dates for the mandatorily redeemable membership interests are the same as those of the SHLLC notes. The sale of the SCCG notes, the membership interests in SCCG, and the SHLLC notes all closed on August 9, 2013. The SCCG notes are secured by TVA’s lease payments, and the SHLLC notes are secured by SHLLC’s investment in, and amounts receivable from, SCCG. TVA’s lease payments to SCCG are payable on the same dates as SCCG’s and SHLLC’s semi-annual debt service payments and are equal to the sum of (i) the amount of SCCG’s semi-annual debt service payments, (ii) the amount of SHLLC’s semi-annual debt service payments, and (iii) the amount of scheduled pre-determined payments to be made to Seven States Southaven, LLC on each lease payment date by SHLLC as agreed in SHLLC’s formation documents (the "Seven States Return"). In addition to the lease payments, TVA pays administrative and miscellaneous expenses incurred by SCCG and SHLLC. Certain agreements related to this transaction contain default and acceleration provisions.
	TVA participated in the design, business conduct, and financial support of SCCG and has determined that it has a direct variable interest in SCCG resulting from risk associated with the value of the Southaven CCF at the end of the lease term. Based on its analysis, TVA has determined that it is the primary beneficiary of SCCG and, as such, is required to account for the VIE on a consolidated basis.
	John Sevier
	On January 17, 2012, TVA entered into a $1.0 billion construction management agreement and lease financing arrangement with John Sevier Combined Cycle Generation LLC ("JSCCG") for the completion and lease by TVA of the John Sevier Combined Cycle Facility ("John Sevier CCF"). JSCCG is a special single-purpose limited liability company formed in January 2012 to finance the John Sevier CCF through a $900 million secured note issuance (the “JSCCG notes”) and the issuance of $100 million of membership interests subject to mandatory redemption.  The membership interests were purchased by John Sevier Holdco LLC ("Holdco").  Holdco is a special single-purpose entity, also formed in January 2012, established to acquire and hold the membership interests in JSCCG.  A non-controlling interest in Holdco is held by a third party through nominal membership interests, to which none of the income, expenses, and cash flows is allocated.
	The membership interests held by Holdco in JSCCG were purchased with proceeds from the issuance of $100 million of secured notes (the “Holdco notes") and are subject to mandatory redemption pursuant to scheduled amortizing, semi-annual payments due each January 15 and July 15, with a final payment due on January 15, 2042. The payment dates for the mandatorily redeemable membership interests are the same as those of the Holdco notes. The sale of the JSCCG notes, the membership interests in JSCCG, and the Holdco notes closed on January 17, 2012. The JSCCG notes are secured by TVA’s lease payments, and the Holdco notes are secured by Holdco's investment in, and amounts receivable from, JSCCG. TVA’s lease payments to JSCCG are equal to and payable on the same dates as JSCCG’s and Holdco’s semi-annual debt service payments. In addition to the lease payments, TVA pays administrative and miscellaneous expenses incurred by JSCCG and Holdco. Certain agreements related to this transaction contain default and acceleration provisions.
	Due to its participation in the design, business conduct, and credit and financial support of JSCCG and Holdco, TVA has determined that it has a variable interest in each of these entities. Based on its analysis, TVA has concluded that it is the primary beneficiary of JSCCG and Holdco and, as such, is required to account for the VIEs on a consolidated basis. Holdco’s membership interests in JSCCG are eliminated in consolidation.

Kingston_Fossil_Plant_Ash_Spil1

Kingston Fossil Plant Ash Spill Kingston Fossil Plant Ash Spill (Policies)	12 Months Ended
	Sep. 30, 2014
Environmental Remediation Obligations [Abstract]	'
Kingston Fossil Plant Ash Spill Policy	'
	Financial Impact
	TVA recorded an estimate of $1.1 billion for the cost of cleanup related to this event.  In August 2009, TVA began using regulatory accounting treatment to defer all actual costs already incurred and expected future costs related to the ash spill.  The cost is being charged to expense as it is collected in rates over 15 years, beginning October 1, 2009.
	Amounts spent since the event through September 30, 2014, totaled $1.1 billion.  The remaining estimated liability at September 30, 2014, was $21 million and is included in Current liabilities.
	TVA has not included the following categories of costs in the above estimate since it has been determined that these costs are currently either not probable or not reasonably estimable: penalties (other than the penalties set out in a June 2010 TDEC order), regulatory directives, natural resources damages (other than payments required under a memorandum of agreement with TDEC and the U.S. Fish and Wildlife Service establishing a process and a method for resolving the natural resource damages claim), future lawsuits, future claims, long-term environmental impact costs, final long-term disposition of the ash processing area, and costs associated with new laws and regulations.  There are certain other costs that will be incurred that have not been included in the estimate as they are appropriately accounted for in other areas of the consolidated financial statements.  Associated capital asset purchases are recorded in property, plant, and equipment.  Ash handling and disposition costs from current plant operations are recorded in operating expenses.  A portion of the dredge cell closure costs are also excluded from the estimate, as they are included in the non-nuclear ARO liability.

Asset_Retirement_Obligations_A

Asset Retirement Obligations Asset Retirement Obligations (Policies)	12 Months Ended
	Sep. 30, 2014
Asset Retirement Obligation [Abstract]	'
Asset Retirement Obligations, Policy [Policy Text Block]	'
	Decommissioning Costs
	TVA recognizes legal obligations associated with the future retirement of certain tangible long-lived assets.  These obligations relate to fossil fuel-fired generating plants, nuclear generating plants, hydroelectric generating plants/dams, transmission structures, and other property-related assets.  These other property-related assets include, but are not limited to, easements and coal rights.  Activities involved with retiring these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site reclamation.  Revisions to the estimates of asset retirement obligations ("AROs") are made whenever factors indicate that the timing or amounts of estimated cash flows have changed.  Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset.  See Note 8 — Nuclear Decommissioning Costs and Non-Nuclear Decommissioning Costs and Note 12.
	To estimate its decommissioning obligation related to its nuclear generating stations, TVA uses a probability-weighted, discounted cash flow model which, on a unit-by-unit basis, considers multiple outcome scenarios that include significant estimations and assumptions. Those assumptions include (1) estimates of the cost of decommissioning, (2) the method of decommissioning and the timing of the related cash flows, (3) the license period of the nuclear plant, considering the probability of license extensions, (4) cost escalation factors, and (5) the credit adjusted risk free rate to measure the obligation at the present value of the future estimated costs. Prior to June 30, 2014, TVA based its decommissioning cost estimates on cost elements prescribed by the NRC to dismantle and decommission the radioactive portion of each site with the assumption that decommissioning would occur within the first seven years after plant shut down, which approximates the DECON method of decommissioning. The DECON method requires that radioactive contamination is removed from a site and safely disposed of or decontaminated to a level that permits the site to be released for unrestricted use shortly after it ceases operation. On June 30, 2014, TVA recorded a change in estimate based on site-specific decommissioning cost studies. Additionally, TVA determined it appropriate to reflect an increase in the probability that certain of its nuclear operating licenses will be extended and that there is a probability that it will be able to delay ultimate decommissioning activities under a SAFSTOR method of decommissioning. The SAFSTOR method allows nuclear facilities to be placed and maintained in a condition that allows the facilities to be safely stored and subsequently decontaminated to levels that permit release for unrestricted use. As such, TVA ascribed probabilities to both the SAFSTOR and DECON methods of decommissioning in order to estimate its decommissioning obligation. Decommissioning cost studies will be updated for each of TVA’s nuclear units at least every five years.

Benefit_Plans_Benefit_Plans_Po

Benefit Plans Benefit Plans (Policies)	12 Months Ended
	Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]	'
Benefit Plans	'
	Accounting Mechanisms
	Regulatory Accounting.  TVA has classified all amounts related to unrecognized prior service costs, net actuarial gains or losses, and the funded status as regulatory assets as such amounts are probable of collection in future rates. In 2015, TVA began including its cash contributions to the pension plan in the rate-making formula; accordingly, on October 1, 2014, TVA began recognizing pension costs as regulatory assets to the extent that the amount calculated under GAAP as pension expense differs from the amount TVA contributes to the pension plan.
	Cost Method. TVA uses the projected unit credit cost method to determine the service cost and the projected benefit obligation for retirement, termination, and ancillary benefits.  Under this method, a “projected accrued benefit” is calculated at the beginning of the year and at the end of the year for each benefit that may be payable in the future.  The “projected accrued benefit” is based on the plan’s accrual formula and upon service at the beginning or end of the year, but it uses final average compensation, social security benefits, and other relevant factors projected to the age at which the employee is assumed to leave active service.  The projected benefit obligation is the actuarial present value of the “projected accrued benefits” at the beginning of the year for employed participants and is the actuarial present value of all benefits for other participants.  The service cost is the actuarial present value of the difference between the “projected accrued benefits” at the beginning and end of the year.
	Amortization of Net Gain or Loss.  TVA utilizes the corridor approach for gain/loss amortization.  Differences between actuarial assumptions and actual plan results are deferred and amortized into periodic cost only when the accumulated differences exceed 10 percent of the greater of the projected benefit obligation or the market-related value of plan assets.  If necessary, the excess is amortized over the average remaining service period of active employees.
	Asset Method.  TVA recognizes the impact of asset performance on pension expense over a three-year phase-in period through a “market-related” value of assets calculation.  Since the “market-related” value of assets recognizes investment gains and losses over a three-year period, the future value of assets will be impacted as previously deferred gains or losses are recognized.  The “market-related” value is used in calculating expected return on plan assets and net gain or loss for pension cost determination.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Allowance for Uncollectible Accounts [Table Text Block]	'
	The following table contains information about TVA’s current estimates related to uncollectible accounts.
	Allowance for Uncollectible Accounts
	(in millions)
			Balance at beginning of year			Additions charged to expense
								Deductions			Balance at end of year
	Description
	For the year ended September 30, 2014
	Allowance for uncollectible accounts
	Receivables		$	1		$	1	$	(1	)	$	1
	Loans		10			—		(1		)	9
	Total allowances deducted from assets		$	11		$	1	$	(2	)	$	10
	For the year ended September 30, 2013
	Allowance for uncollectible accounts
	Receivables		$	7		$	—	$	(6	)	$	1
	Loans		12			—		(2		)	10
	Total allowances deducted from assets		$	19		$	—	$	(8	)	$	11
	For the year ended September 30, 2012
	Allowance for uncollectible accounts
	Receivables		$	1		$	6	$	—		$	7
	Loans		11			1		—			12
	Total allowances deducted from assets		$	12		$	7	$	—		$	19
Property, Plant, and Equipment Depreciation Rates	'
	Average depreciation rates by asset class are as follows:
	Property, Plant, and Equipment Depreciation Rates
	At September 30
	(percent)
		2014			2013		2012
	Asset Class
	Nuclear	2.9			2.86		2.71
	Coal-Fired	4.37			3.47		5.65
	Hydroelectric	1.44			1.3		1.35
	Gas and oil-fired	3.23			3.21		3.67
	Transmission	2.76			2.76		2.99
	Other	8.4			8.14		8.1

Restructuring_Tables

Restructuring (Tables)	12 Months Ended
	Sep. 30, 2014
Restructuring and Related Activities [Abstract]	'
Severance Cost Liability Activity	'
	The table below summarizes the activity related to severance costs:
	Severance Cost Liability
	For the year ended September 30
		2014
	Severance cost liability at beginning of period	$	—
	Liabilities incurred during the period	65
	Actual costs paid during the period	(20		)
	Severance cost liability at end of period	$	45

Accounts_Receivable_Net_Accoun

Accounts Receivable, Net Accounts Receivable, Net (Tables)	12 Months Ended
	Sep. 30, 2014
Accounts Receivable, Net [Abstract]	'
Accounts Receivable, Net	'
	The table below summarizes the types and amounts of TVA’s accounts receivable:
	Accounts Receivable, Net
	At September 30
		2014			2013
	Power receivables	$	1,576		$	1,495
	Other receivables	101			73
	Allowance for uncollectible accounts	(1		)	(1		)
	Accounts receivable, net	$	1,676		$	1,567

Inventories_Net_Inventories_Ne

Inventories, Net Inventories, Net (Tables)	12 Months Ended
	Sep. 30, 2014
Inventory, Net [Abstract]	'
Inventories, Net	'
	The table below summarizes the types and amounts of TVA’s inventories:
	Inventories, Net
	At September 30
		2014			2013
	Materials and supplies inventory	$	616		$	620
	Fuel inventory	473			494
	Emission allowance inventory	13			14
	Allowance for inventory obsolescence	(46		)	(37		)
	Inventories, net	$	1,056		$	1,091

Net_Completed_Plant_Net_Comple

Net Completed Plant Net Completed Plant (Tables)	12 Months Ended
	Sep. 30, 2014
Net Completed Plant [Abstract]	'
Net Completed Plant	'
	Net completed plant consisted of the following:
	Net Completed Plant
	At September 30
		2014						2013
		Cost		Accumulated Depreciation				Cost		Accumulated Depreciation		Net
						Net
	Coal-fired	$	14,078	$	9,065	$	5,013	$	13,847	$	8,429	$	5,418
	Gas and oil-fired	3,411		1,094		2,317		3,386		1,008		2,378
	Nuclear	18,489		9,593		8,896		18,725		9,103		9,622
	Transmission	6,519		2,683		3,836		6,300		2,562		3,738
	Hydroelectric	2,547		889		1,658		2,392		892		1,500
	Other electrical plant	1,550		885		665		1,452		792		660
	Subtotal	46,594		24,209		22,385		46,102		22,786		23,316
	Multipurpose dams	928		364		564		928		356		572
	Other stewardship	42		16		26		43		15		28
	Subtotal	970		380		590		971		371		600
	Total	$	47,564	$	24,589	$	22,975	$	47,073	$	23,157	$	23,916

Other_LongTerm_Assets_Other_Lo

Other Long-Term Assets Other Long-Term Assets (Tables)	12 Months Ended
	Sep. 30, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]	'
Other Long-Term Assets	'
	The table below summarizes the types and amounts of TVA’s other long-term assets:
	Other Long-Term Assets
	At September 30
		2014		2013
	EnergyRight® receivables	$	123	$	117
	Unamortized debt issue cost of power bonds	68		75
	Loans and other long-term receivables, net	87		73
	Coal contract derivative assets	—		1
	Prepaid capacity payments	58		62
	Currency swap assets, net	—		28
	Restricted cash	64		—
	Other	83		89
	Total other long-term assets	$	483	$	445

Regulatory_Assets_and_Liabilit1

Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Tables)	12 Months Ended
	Sep. 30, 2014
Regulatory Assets and Liabilities Disclosure [Abstract]	'
Regulatory Assets and Liabilities	'
	Components of regulatory assets and regulatory liabilities are summarized in the table below.
	Regulatory Assets and Liabilities
	At September 30
		2014		2013
	Current regulatory assets
	Unrealized losses on commodity derivatives	$	134	$	183
	Deferred nuclear generating units	237		237
	Environmental agreements	54		73
	Fuel cost adjustment receivable	9		—
	Environmental cleanup costs – Kingston ash spill	47		68
	Total current regulatory assets	481		561
	Non-current regulatory assets
	Deferred pension costs and other post-retirement benefits costs	4,297		4,076
	Unrealized losses on interest rate derivatives	957		808
	Nuclear decommissioning costs	931		893
	Environmental cleanup costs - Kingston ash spill	421		681
	Non-nuclear decommissioning costs	645		571
	Deferred nuclear generating units	1,255		1,438
	Unrealized losses on commodity derivatives	72		139
	Environmental agreements	108		189
	Other non-current regulatory assets	308		336
	Total non-current regulatory assets	8,994		9,131
	Total regulatory assets	$	9,475	$	9,692
	Current regulatory liabilities
	Fuel cost adjustment tax equivalents	$	182	$	176
	Fuel cost adjustment liability	—		29
	Unrealized gains on commodity derivatives	2		7
	Total current regulatory liabilities	184		212
	Non-current regulatory liabilities
	Unrealized gains on commodity derivatives	—		1
	Total non-current regulatory liabilities	—		1
	Total regulatory liabilities	$	184	$	213

Variable_Interest_Entities_Var1

Variable Interest Entities Variable Interest Entities (Tables)	12 Months Ended
	Sep. 30, 2014
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]	'
Variable Interest Entities	'
	The financial statement items attributable to carrying amounts and classifications of JSCCG, Holdco, and SCCG as of September 30, 2014 and 2013, as reflected in the Consolidated Balance Sheets, are as follows:
	Summary of Impact of VIEs on Consolidated Balance Sheets
	At September 30
		2014		2013
	Current liabilities of VIE
	Accrued interest of VIE	$	12	$	12
	Current portion of membership interests of VIE subject to mandatory redemption	2		2
	Current maturities of long-term debt of VIE	32		30
	Total current liabilities of VIE	46		44
	Other liabilities of VIE
	Membership interests of VIE subject to mandatory redemption	37		38
	Long-term debt of VIE, net
	Long-term debt of VIE	1,279		1,311
	Total liabilities of VIE	$	1,362	$	1,393

Other_LongTerm_Liabilities_Oth

Other Long-Term Liabilities Other Long-Term Liabilities (Tables)	12 Months Ended
	Sep. 30, 2014
Other Liabilities, Noncurrent [Abstract]	'
Other Long-Term Liabilities	'
	The table below summarizes the types and amounts of Other long-term liabilities:
	Other Long-Term Liabilities
	At September 30
		2014		2013
	Interest rate swap liabilities	$	1,348	$	1,199
	Environmental Agreements liability	108		190
	EnergyRight® financing obligation	152		149
	Membership interests of VIE subject to mandatory redemption	37		38
	Commodity contract derivative liabilities	17		35
	Commodity swap derivative liabilities	14		36
	Currency swap liabilities	15		15
	Other	271		199
	Total other long-term liabilities	$	1,962	$	1,861

Asset_Retirement_Obligations_A1

Asset Retirement Obligations Asset Retirement Obligations (Tables)	12 Months Ended
	Sep. 30, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]	'
Asset Retirement Obligations	'
	Asset Retirement Obligation Activity
		Nuclear			Non-Nuclear			Total
	Balance at September 30, 2012	$	2,208		$	1,081		$	3,289
	Settlements (ash storage areas)	—			(37		)	(37		)
	Change in estimate (ash storage areas)	66			—			66
	Accretion (recorded to regulatory asset)	125			45			170
	Balance at September 30, 2013	$	2,399		$	1,089		$	3,488
	Settlements (ash storage areas)	—			(14		)	(14		)
	Change in estimate as a result of nuclear site-specific studies	(472		)	—			(472		)
	Change in estimate (ash storage areas)	—			(10		)	(10		)
	Accretion (recorded to regulatory asset)	125			52			177
	Balance at September 30, 2014	$	2,052		$	1,117		$	3,169		(1)
	Note
	(1) The current portion of ARO in the amount of $80 million is included in Accounts payable and accrued liabilities.

Debt_and_Other_Obligations_Deb

Debt and Other Obligations Debt and Other Obligations (Tables)	12 Months Ended
	Sep. 30, 2014
Debt and Other Obligations [Abstract]	'
Debt Securities Activity	'
	The table below summarizes the long-term debt securities activity for the period from October 1, 2012, to September 30, 2014.
	Debt Securities Activity
	For the years ended September 30
			2014				2013
	Issues
	Variable interest entities		$	—			$	360
	electronotes®		—				152
	2012 Series B(1)		—				1,000
	2013 Series A(2)		—				1,000
	2014 Series A(3)		1,000				—
	Discount on debt issues		(11		)		(30		)
	Total		$	989			$	2,482
	Redemptions/Maturities(4)
	Variable interest entities		$	30			$	13
	electronotes®		335				50
	1998 Series C		—				1,359
	1998 Series D		—				2
	1999 Series A		—				1
	2003 Series C		—				940
	2009 Series A		4				4
	2009 Series B		26				2
	Total		$	395			$	2,371
	Notes
	(1) The 2012 Series B bonds were issued at 97.49 percent of par.
	(2) The 2013 Series A bonds were issued at 99.52 percent of par.
	(3) The 2014 Series A bonds were issued at 98.94 percent of par.
	(4) All redemptions were at 100 percent of par.
Debt Outstanding	'
	Total debt outstanding at September 30, 2014, and 2013, consisted of the following:
	Short-Term Debt
	At September 30
					Call/(Put) Date				2014				2013
	CUSIP or Other Identifier		Maturity				Coupon Rate
	Short-term debt, net of discounts								$	596			$	2,432
	Current maturities of long-term debt of variable interest entities issued at par								32				30
	Current maturities of power bonds issued at par
	880591EE8		11/15/14				2.25%		3				3
	880591EF5		12/15/14				3.77%		26				26
	880591DY5		6/15/15				4.38%		1,000				—
	88059TEL1		11/15/14				2.65%		3				3
	Total current maturities of power bonds issued at par								1,032				32
	Total current debt outstanding, net								$	1,660			$	2,494
	Long-Term Debt(1)
	At September 30
					Coupon			Call Date		2014 Par				2013 Par			Stock Exchange Listings
	CUSIP or Other Identifier		Maturity		Rate
	electronotes®(2)		05/15/2020 -		2.375 - 4.375%			2/15/2015 -		$	387			$	723		None
			2/15/43					2/15/18
	880591DY5		6/15/15		4.38%					—				1,000			New York, Luxembourg
	880591EE8(3)		11/15/15		2.25%					2				4			None
	880591DS8		12/15/16		4.88%					524				524			New York
	880591EA6		7/18/17		5.50%					1,000				1,000			New York, Luxembourg
	880591CU4		12/15/17		6.25%					650				650			New York
	880591EC2		4/1/18		4.50%					1,000				1,000			New York, Luxembourg
	880591EQ1		10/15/18		1.75%					1,000				1,000			New York
	880591EL2		2/15/21		3.88%					1,500				1,500			New York
	880591DC3		6/7/21		5.81%	(4	)			324				324			New York, Luxembourg
	880591EN8		8/15/22		1.88%					1,000				1,000			New York
	880591ER9		9/15/24		2.88%					1,000				—			New York
	880591CJ9		11/1/25		6.75%					1,350				1,350			New York, Hong Kong, Luxembourg, Singapore
	880591300(5)		6/1/28		3.83%					324				324			New York
	880591409(5)		5/1/29		3.96%					270				270			New York
	880591DM1		5/1/30		7.12%					1,000				1,000			New York, Luxembourg
	880591DP4		6/7/32		6.59%	(4	)			406				405			New York, Luxembourg
	880591DV1		7/15/33		4.70%					472				472			New York, Luxembourg
	880591EF5(3)		6/15/34		3.77%					388				414			None
	880591DX7		6/15/35		4.65%					436				436			New York
	880591CK6		4/1/36		5.98%					121				121			New York
	880591CS9		4/1/36		5.88%					1,500				1,500			New York
	880591CP5		1/15/38		6.15%					1,000				1,000			New York
	880591ED0		6/15/38		5.50%					500				500			New York
	880591EH1		9/15/39		5.25%					2,000				2,000			New York
	880591EP3		12/15/42		3.50%					1,000				1,000			New York
	880591DU3		6/7/43		4.96%	(4	)			243				243			New York, Luxembourg
	880591CF7		7/15/45		6.24%			7/15/20		140				140			New York
	880591EB4		1/15/48		4.88%					500				500			New York, Luxembourg
	880591DZ2		4/1/56		5.38%					1,000				1,000			New York
	880591EJ7		9/15/60		4.63%					1,000				1,000			New York
	Subtotal									22,037				22,400
	Unamortized discounts, premiums, and other									(89		)		(85		)
	Total long-term outstanding power bonds, net									21,948				22,315
	Long-term debt of variable interest entities									1,279				1,311
	Total long-term debt, net									$	23,227			$	23,626
	Notes
	(1)  Includes net exchange losses from currency transactions of $44 million at September 30, 2014 and $43 million at September 30, 2013.
	(2)  Includes one electronotes® issue with partial maturities of principal for each required annual payment.
	(3)  These Bonds include partial maturities of principal for each required annual payment.
	(4)  The coupon rate represents TVA’s effective interest rate.
	(5)  TVA PARRS, CUSIP numbers 880591300 and 880591409, may be redeemed under certain conditions.  See Put and Call Options.
Maturities Due	'
	Maturities Due in the Year Ending September 30
		2015				2016				2017				2018			2019		Thereafter		Total
	Long-term power bonds and long-term debt of variable interest entities including current maturities(1)	$	1,064			$	65			$	1,590			$	1,718		$	1,070	$	18,829	$	24,336
	Short-term debt, net of discounts	596				—				—				—			—		—		596
	Note
	(1) Does not include noncash items of foreign currency exchange loss of $44 million and net discount on sale of Bonds of $89 million.

Risk_Management_Activities_and1

Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions (Tables)	12 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Summary of Derivative Instruments That Receive Hedge Accounting Treatment	'
	The following tables summarize the accounting treatment that certain of TVA's financial derivative transactions receive.
	Summary of Derivative Instruments That Receive Hedge Accounting Treatment (part 1)
	Amount of Mark-to-Market Gain (Loss) Recognized in Other Comprehensive Income (Loss)
	For the years ended September 30
	Derivatives in Cash Flow Hedging Relationship		Objective of Hedge Transaction		Accounting for Derivative		2014				2013
					Hedging Instrument
	Currency swaps		To protect against changes in cash flows caused by changes in foreign currency exchange rates (exchange rate risk)		Unrealized gains and losses are recorded in AOCI and reclassified to interest expense to the extent they are offset by gains and losses on the hedged transaction		$	4			$	78
	Summary of Derivative Instruments That Receive Hedge Accounting Treatment (part 2)
	Amount of Gain (Loss) Reclassified from OCI to Interest Expense
	For the years ended September 30
	Derivatives in Cash Flow Hedging Relationship		2014				2013
	Currency swaps		$	2			$	1
	Note
	There were no ineffective portions or amounts excluded from effectiveness testing for any of the periods presented. Based on forecasted foreign currency exchange rates, TVA expects to reclassify approximately $37 million of losses from AOCI to interest expense within the next twelve months to offset amounts anticipated to be recorded in interest expense related to exchange gain on the debt.
	Summary of Derivative Instruments That Do Not Receive Hedge Accounting Treatment
	Amount of Gain (Loss) Recognized in Income on Derivatives(1)
	For the years ended September 30
	Derivative Type		Objective of Derivative		Accounting for Derivative Instrument		2014				2013
	Interest rate swaps		To fix short-term debt variable rate to a fixed rate (interest rate risk)		MtM gains and losses are recorded as regulatory assets or liabilities until settlement, at which time the gains/losses are recognized in gain/loss on derivative contracts.(2)		$	—			$	—
	Commodity contract derivatives		To protect against fluctuations in market prices of purchased coal or natural gas  (price risk)		MtM gains and losses are recorded as regulatory assets or liabilities. Realized gains and losses due to contract settlements are recognized in fuel expense as incurred.		(64		)		(11		)
	Commodity derivatives		To protect against fluctuations in market prices of purchased commodities (price risk)		MtM gains and losses are recorded as regulatory assets or liabilities. Realized gains and losses are recognized in fuel expense or purchased power expense when the related commodity is used in production.		(43		)		(126		)
	under FTP
Summary of Derivative Instruments That Do Not Receive Hedge Accounting Treatment	'
	Summary of Derivative Instruments That Do Not Receive Hedge Accounting Treatment
	Amount of Gain (Loss) Recognized in Income on Derivatives(1)
	For the years ended September 30
	Derivative Type		Objective of Derivative		Accounting for Derivative Instrument		2014				2013
	Interest rate swaps		To fix short-term debt variable rate to a fixed rate (interest rate risk)		MtM gains and losses are recorded as regulatory assets or liabilities until settlement, at which time the gains/losses are recognized in gain/loss on derivative contracts.(2)		$	—			$	—
	Commodity contract derivatives		To protect against fluctuations in market prices of purchased coal or natural gas  (price risk)		MtM gains and losses are recorded as regulatory assets or liabilities. Realized gains and losses due to contract settlements are recognized in fuel expense as incurred.		(64		)		(11		)
	Commodity derivatives		To protect against fluctuations in market prices of purchased commodities (price risk)		MtM gains and losses are recorded as regulatory assets or liabilities. Realized gains and losses are recognized in fuel expense or purchased power expense when the related commodity is used in production.		(43		)		(126		)
	under FTP
	Notes
	(1) All of TVA's derivative instruments that do not receive hedge accounting treatment have unrealized gains (losses) that would otherwise be recognized in income but instead are deferred as regulatory assets and liabilities. As such, there was no related gain (loss) recognized in income for these unrealized gains (losses) for the years ended 2014 and 2013.
	(2) Generally, TVA maintains a level of outstanding discount notes equal to or greater than the notional amount of the interest rate swaps. However, in September 2014 TVA issued long-term Bonds in anticipation of the maturity of other long-term debt, and used the proceeds to pay down discount notes, which caused the balance of discount notes outstanding at September 30, 2014, to fall below the notional amount of the interest rate swaps. There is no impact on the statements of operations due to the use of regulatory accounting for these items.
Mark-to-Market Value of TVA Derivatives	'
	Mark-to-Market Values of TVA Derivatives
	At September 30
		2014						2013
	Derivatives that Receive Hedge Accounting Treatment:
		Balance				Balance Sheet Presentation		Balance				Balance Sheet Presentation
	Currency swaps
	£200 million Sterling	$	(15	)		Other long-term liabilities		$	(15	)		Other long-term liabilities
	£250 million Sterling	56				Other long-term assets		51				Other long-term assets
	£150 million Sterling	8				Other long-term assets		10				Other long-term assets
	Derivatives that Do Not Receive Hedge Accounting Treatment:
		Balance				Balance Sheet Presentation		Balance				Balance Sheet Presentation
	Interest rate swaps
	$1.0 billion notional	(987		)		Other long-term liabilities		(886		)		Other long-term liabilities
	$476 million notional	(349		)		Other long-term liabilities		(300		)		Other long-term liabilities
	$42 million notional	(12		)		Other long-term liabilities		(13		)		Other long-term liabilities
	Commodity contract derivatives	(96		)		Other current assets $1; Other long-term liabilities $(17); Accounts payable and accrued liabilities $(80)		(141		)		Other long-term assets $1; Other current assets $2; Other long-term liabilities $(35); Accounts payable and accrued liabilities $(109)
	FTP
	Derivatives under FTP(1)	(103		)		Other current assets $(69); Other long-term liabilities $(14); Accounts payable and accrued liabilities $(20)		(166		)		Other current assets $(97); Other long-term liabilities $(36); Accounts payable and accrued liabilities $(33)
	Note
	(1)   Fair values of certain derivatives under the FTP that were in net liability positions totaling $69 million and $100 million at September 30, 2014 and September 30, 2013, respectively, are recorded in TVA's margin cash accounts in Other current assets. These derivatives are transacted with futures commission merchants, and cash deposits have been posted to the margin cash accounts held with each futures commission merchant to offset the net liability positions in full.
Currency Swaps Outstanding	'
	TVA had the following currency swaps outstanding at September 30, 2014:
	Currency Swaps Outstanding
	At September 30, 2014
	Effective Date of Currency Swap Contract		Associated TVA Bond Issues Currency Exposure		Expiration Date of Swap		Overall Effective
							Cost to TVA
	1999		£200 million		2021		5.81%
	2001		£250 million		2032		6.59%
	2003		£150 million		2043		4.96%
Commodity Contract Derivatives	'
	Commodity Contract Derivatives
	At September 30
		2014								2013
		Number of Contracts		Notional Amount		Fair Value (MtM)				Number of Contracts		Notional Amount		Fair Value (MtM)
	Coal contract derivatives	24		31 million tons		$	(86	)		19		43 million tons		$	(140	)
	Natural gas contract derivatives	46		62 million mmBtu		$	(10	)		13		39 million mmBtu		$	(1	)
Derivatives Under Financial Trading Program	'
	Derivatives under Financial Trading Program
	At September 30
		2014							2013
		Notional Amount			Fair Value (MtM)				Notional Amount			Fair Value (MtM)
					(in millions)							(in millions)
	Natural gas (in mmBtu)
	Futures contracts	—			$	—			—			$	—
	Swap contracts	102,227,500			(103		)		152,922,500			(169		)
	Option contracts	—			—				—			—
	Natural gas financial positions	102,227,500			$	(103	)		152,922,500			$	(169	)
	Fuel oil/crude oil (in barrels)
	Futures contracts	—			$	—			—			$	—
	Swap contracts	—			—				1,205,000			3
	Option contracts	—			—				—			—
	Fuel oil/crude oil financial positions	—			$	—			1,205,000			$	3
	Note
	Due to the right of setoff and method of settlement, TVA elects to record commodity derivatives under the FTP based on its net commodity position with the broker or other counterparty.  Notional amounts disclosed represent the net absolute value of contractual amounts.
FTP Unrealized Gains (Losses)	'
	Financial Trading Program Unrealized Gains (Losses)
	At September 30
	FTP unrealized gains (losses) deferred as regulatory liabilities (assets)		2014				2013
	Natural gas		$	(103	)		$	(169	)
	Fuel oil/crude oil		—				3
	Coal		—				—
FTP Realized Gains (Losses)	'
	Financial Trading Program Realized Gains (Losses)
	For the years ended September 30
	Decrease (increase) in fuel expense		2014				2013
	Natural gas		$	(34	)		$	(78	)
	Fuel oil/crude oil		2				4
	Coal		—				(1		)
	Financial Trading Program Realized Gains (Losses)
	For the years ended September 30
	Decrease (increase) in purchased power expense		2014				2013
	Natural gas		$	(11	)		$	(51	)
Offsetting Assets and Liabilities [Table Text Block]	'
	The amounts of TVA's derivative instruments as reported in the Consolidated Balance Sheets as of September 30, 2014, and September 30, 2013, are shown in the table below.
		As of September 30, 2014
		Gross Amounts of Recognized Assets/Liabilities				Gross Amounts Offset in the Balance Sheet (1)				Net Amounts of Assets/Liabilities Presented in the Balance Sheet (2)
	Assets
	Currency swaps	$	64			$	(64	)		$	—
	Commodity derivatives under FTP	51				(51		)		—
	Total derivatives subject to master netting or similar arrangement	115				(115		)		—
	Total derivatives not subject to master netting or similar arrangement	1				—				1
	Total	$	116			$	(115	)		$	1
	Liabilities
	Currency swap (3)	$	(15	)		$	—			$	(15	)
	Interest rate swaps (3)	(1,348		)		—				(1,348		)
	Commodity derivatives under FTP	(154		)		120				(34		)
	Total derivatives subject to master netting or similar arrangement	(1,517		)		120				(1,397		)
	Total derivatives not subject to master netting or similar arrangement	(97		)		—				(97		)
	Total	$	(1,614	)		$	120			$	(1,494	)
		As of September 30, 2013
		Gross Amounts of Recognized Assets/Liabilities				Gross Amounts Offset in the Balance Sheet (1)				Net Amounts of Assets/Liabilities Presented in the Balance Sheet (2)
	Assets
	Currency swaps	$	61			$	(33	)		$	28
	Commodity derivatives under FTP	101				(98		)		3
	Total derivatives subject to master netting or similar arrangement	162				(131		)		31
	Total derivatives not subject to master netting or similar arrangement	3				—				3
	Total	$	165			$	(131	)		$	34
	Liabilities
	Currency swap (3)	$	(15	)		$	—			$	(15	)
	Interest rate swaps (3)	(1,199		)		—				(1,199		)
	Commodity derivatives under FTP	(267		)		198				(69		)
	Total derivatives subject to master netting or similar arrangement	(1,481		)		198				(1,283		)
	Total derivatives not subject to master netting or similar arrangement	(144		)		—				(144		)
	Total	$	(1,625	)		$	198			$	(1,427	)
	Notes
	(1) Amounts primarily include counterparty netting of derivative contracts, margin account deposits for futures commission merchants transactions, and cash collateral received or paid in accordance with the accounting guidance for derivatives and hedging transactions.
	(2) There are no derivative contracts subject to a master netting arrangement or similar agreement which are not offset in the balance sheets.
	(3) Letters of credit of approximately $1.0 billion and $800 million were posted as collateral at September 30, 2014 and September 30, 2013, respectively, to partially secure the liability positions of one of the currency swaps and one of the interest rate swaps in accordance with the collateral requirements for these derivatives.

Fair_Value_Measurements_Fair_V

Fair Value Measurements Fair Value Measurements - (Tables)	12 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Valuation Techniques	'
	The measurement of fair value results in classification into a hierarchy by the inputs used to determine the fair value as follows:
	Level 1	—		Unadjusted quoted prices in active markets accessible by the reporting entity for identical assets or liabilities.  Active markets are those in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing.
	Level 2	—		Pricing inputs other than quoted market prices included in Level 1 that are based on observable market data and that are directly or indirectly observable for substantially the full term of the asset or liability.  These include quoted market prices for similar assets or liabilities, quoted market prices for identical or similar assets in markets that are not active, adjusted quoted market prices, inputs from observable data such as interest rate and yield curves, volatilities and default rates observable at commonly quoted intervals, and inputs derived from observable market data by correlation or other means.
	Level 3	—		Pricing inputs that are unobservable, or less observable, from objective sources.  Unobservable inputs are only to be used to the extent observable inputs are not available.  These inputs maintain the concept of an exit price from the perspective of a market participant and should reflect assumptions of other market participants.  An entity should consider all market participant assumptions that are available without unreasonable cost and effort.  These are given the lowest priority and are generally used in internally developed methodologies to generate management's best estimate of the fair value when no observable market data is available.
Unrealized Investment Gains (Losses)	'
	TVA recorded unrealized gains and losses related to its trading securities held as of the end of each period as follows:
		Unrealized Investment Gains (Losses)
		At September 30
		Financial Statement Presentation		2014				2013
	SERP	Other income (expense)		$	1			$	2
	LTDCP	Other income (expense)		—				—
	NDT	Regulatory asset		35				48
	ART	Regulatory asset		15				33
Fair Value Measurements	'
	Fair Value Measurements
	At September 30, 2014
	Assets	Quoted Prices in Active				Significant Other				Significant				Total
		Markets for				Observable Inputs				Unobservable
		Identical Assets				(Level 2)				Inputs
		(Level 1)								(Level 3)
	Investments
	Equity securities	$	162			$	—			$	—			$	162
	Debt securities
	U.S. government corporations and	46				39				—				85
	agencies
	Corporate debt securities	—				290				—				290
	Residential mortgage-backed securities	—				14				—				14
	Commercial mortgage-backed securities	—				7				—				7
	Collateralized debt obligations	—				29				—				29
	Private partnerships	—				—				214				214
	Commingled funds(2)													—
	Equity security commingled funds	40				903				—				943
	Debt security commingled funds	61				176				—				237
	Total investments	309				1,458				214				1,981
	Currency swaps(1)	—				—				—				—
	Commodity contract derivatives	—				—				1				1
	Commodity derivatives under FTP(1)
	Swap contracts	—				—				—				—
	Total commodity derivatives under FTP	—				—				—				—
	Total	$	309			$	1,458			$	215			$	1,982
	Liabilities	Quoted Prices in Active Markets for Identical Liabilities				Significant Other				Significant				Total
		(Level 1)				Observable Inputs				Unobservable
						(Level 2)				Inputs
										(Level 3)
	Currency swaps(1)	$	—			$	15			$	—			$	15
	Interest rate swaps	—				1,348				—				1,348
	Commodity contract derivatives	—				—				97				97
	Commodity derivatives under FTP(1)
	Swap contracts	—				34				—				34
	Total commodity derivatives under FTP	—				34				—				34
	Total	$	—			$	1,397			$	97			$	1,494
	Notes
	(1)  Due to the right of setoff and method of settlement, TVA elects to record commodity derivatives under the FTP based on its net commodity position with the counterparty or FCM. Deposits are made to TVA's margin cash accounts held with each FCM to offset any net liability positions in full for derivatives that are transacted with FCMs. TVA records currency swaps net of cash collateral received from or paid to the counterparty. See Note 15 — Offsetting of Derivative Assets and Liabilities.
	(2) Commingled funds represent investment funds comprising multiple individual financial instruments and are classified in the table based on their existing investment portfolio as of the measurement date.  Commingled funds primarily composed of one class of security are classified in that category.
	Fair Value Measurements
	At September 30, 2013
	Assets	Quoted Prices in Active				Significant Other				Significant				Total
		Markets for				Observable Inputs				Unobservable
		Identical Assets				(Level 2)				Inputs
		(Level 1)								(Level 3)
	Investments
	Equity securities	$	151			$	—			$	—			$	151
	Debt securities
	U.S. government corporations and	38				67				—				105
	agencies
	Corporate debt securities	—				255				—				255
	Residential mortgage-backed securities	—				25				—				25
	Commercial mortgage-backed securities	—				7				—				7
	Collateralized debt obligations	—				10				—				10
	Private partnerships	—				—				159				159
	Commingled funds(2)													—
	Equity security commingled funds	—				741				—				741
	Debt security commingled funds	—				248				—				248
	Total investments	189				1,353				159				1,701
	Currency swaps(1)	—				28				—				28
	Commodity contract derivatives	—				—				3				3
	Commodity derivatives under FTP(1)
Swap contracts	—				3				—				3
Total commodity derivatives under FTP	—				3				—				3
Total	$	189			$	1,384			$	162			$	1,735
Liabilities	Quoted Prices in Active Markets for Identical Liabilities				Significant Other				Significant				Total
	(Level 1)				Observable Inputs				Unobservable
					(Level 2)				Inputs
									(Level 3)
Currency swaps(1)	$	—			$	15			$	—			$	15
Interest rate swaps	—				1,199				—				1,199
Commodity contract derivatives	—				1				143				144
Commodity derivatives under FTP(1)
Swap contracts	—				69				—				69
Total commodity derivatives under FTP	—				69				—				69
Total	$	—			$	1,284			$	143			$	1,427
Notes
(1)  Due to the right of setoff and method of settlement, TVA elects to record commodity derivatives under the FTP based on its net commodity position with the counterparty or FCM. Deposits are made to TVA's margin cash accounts held with each FCM to offset any net liability positions in full for derivatives that are transacted with FCMs. TVA records currency swaps net of cash collateral received from or paid to the counterparty. See Note 15 — Offsetting of Derivative Assets and Liabilities.
(2) Commingled funds represent investment funds comprising multiple individual financial instruments and are classified in the table based on their existing investment portfolio as of the measurement date.  Commingled funds primarily composed of one class of security are classified in that category.
Fair Value Measurements Using Significant Unobservable Inputs	'
	The following table presents a reconciliation of all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3):
	Fair Value Measurements Using Significant Unobservable Inputs
		Private				Commodity Contract Derivatives
		Partnerships
	Balance at October 1, 2012	$	53			$	(267	)
	Purchases	101				—
	Issuances	—				—
	Sales	(4		)		—
	Settlements	—				—
	Net unrealized gains (losses) deferred as regulatory assets and liabilities	9				127
	Balance at September 30, 2013	159				(140		)
	Purchases	39				—
	Issuances	—				—
	Sales	(9		)		—
	Settlements	—				33
	Net unrealized gains (losses) deferred as regulatory assets and liabilities	25				11
	Balance at September 30, 2014	$	214			$	(96	)
Quantitative Information about Level 3 Fair Value Measurements	'
	The following table presents quantitative information related to the significant unobservable inputs used in the measurement of fair value of TVA's assets and liabilities classified as Level 3 in the fair value hierarchy:
	Quantitative Information about Level 3 Fair Value Measurements
		Fair Value at September 30 2014				Valuation Technique(s)		Unobservable Inputs		Range
	Assets
	Commodity contract derivatives	$	1			Discounted cash flow		Credit risk		2 - 5 %	(1)
						Pricing model		Coal supply and demand		1.0 - 1.1 billion tons/year
								Long-term market prices		$11.24 - $67.07/ton
	Liabilities
	Commodity contract derivatives	$	97			Pricing model		Coal supply and demand		1.0 - 1.1 billion tons/year
								Long-term market prices		$11.24 - $67.07/ton
	Note
	(1) Applies to two contracts.
	Quantitative Information about Level 3 Fair Value Measurements
		Fair Value at September 30 2013				Valuation Technique(s)		Unobservable Inputs		Range
	Assets
	Commodity contract derivatives	$	3			Discounted cash flow		Credit risk		21	%	(1)
						Pricing model		Coal supply and demand		0.9 - 1.0 billion tons/year
								Long-term market prices		$10.25 - $85.25/ton
	Liabilities
	Commodity contract derivatives	$	143			Pricing model		Coal supply and demand		0.9 - 1.0 billion tons/year
								Long-term market prices		$10.25 - $85.25/ton
	Note
	(1) Applies to only one contract.
Estimated Values of Financial Instruments Not Recorded at Fair Value	'
	The estimated values of TVA's financial instruments not recorded at fair value at September 30, 2014, and September 30, 2013, were as follows:
	Estimated Values of Financial Instruments Not Recorded at Fair Value
	At September 30
				2014								2013
		Valuation Classification		Carrying				Fair				Carrying				Fair
				Amount				Value				Amount				Value
	EnergyRight® receivables (including current portion)	Level 2		$	156			$	166			$	150			$	150
	Loans and other long-term receivables, net (including current portion)	Level 2		$	92			$	81			$	73			$	67
	EnergyRight® purchase obligation (including current portion)	Level 2		$	190			$	215			$	186			$	222
	Unfunded loan commitments	Level 2		$	—			$	18			$	—			$	13
	Membership interests of variable interest entity subject to mandatory redemption (including current portion)	Level 2		$	39			$	50			$	40			$	50
	Long-term outstanding power bonds (including current maturities), net	Level 2		$	22,980			$	26,889			$	22,347			$	24,603
	Long-term debt of variable interest entities (including current maturities)	Level 2		$	1,311			$	1,425			$	1,341			$	1,386

Proprietary_Capital_Proprietar

Proprietary Capital Proprietary Capital (Tables)	12 Months Ended
	Sep. 30, 2014
Stockholders' Equity Note [Abstract]	'
Summary of Proprietary Capital Activity	'
	The table below summarizes TVA's activities related to appropriated funds.
	Summary of Proprietary Capital Activity
	At or for the years ended September 30
		2014						2013
	Appropriation Investment	Power Program			Nonpower			Power Program			Nonpower
					Programs						Programs
	Balance at beginning of year	$	268		$	4,351		$	288		$	4,351
	Return of power program appropriation investment	(10		)	—			(20		)	—
	Balance at end of year	258			4,351			268			4,351
	Retained Earnings
	Balance at beginning of year	4,767			(3,742		)	4,492			(3,731		)
	Net income (expense) for year	477			(8		)	282			(11		)
	Return on power program appropriation investment	(4		)	—			(7		)	—
	Balance at end of year	5,240			(3,750		)	4,767			(3,742		)
	Net proprietary capital at September 30	$	5,498		$	601		$	5,035		$	609

Other_Income_Expense_Net_Other

Other Income (Expense), Net Other Income (Expense), Net (Tables)	12 Months Ended
	Sep. 30, 2014
Other Income and Expenses [Abstract]	'
Other Income (Expense), Net	'
	Income and expenses not related to TVA’s operating activities are summarized in the following table:
	Other Income (Expense), Net
	For the years ended September 30
		2014		2013			2012
	Interest income	$	23	$	23		$	21
	External services	19		18			7
	Gains (losses) on investments	6		4			5
	Miscellaneous	1		(1		)	—
	Total other income (expense), net	$	49	$	44		$	33

Benefit_Plans_Benefit_Plans_Ta

Benefit Plans Benefit Plans (Tables)	12 Months Ended
	Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]	'
Obligations and Funded Status	'
	The changes in plan obligations, assets, and funded status for the years ended September 30, 2014 and 2013, were as follows:
	Obligations and Funded Status
	For the years ended September 30
		Pension Benefits								Other Post-Retirement Benefits
		2014				2013				2014			2013
	Change in benefit obligation
	Benefit obligation at beginning of year	$	11,471			$	11,995			$	656		$	811
	Service cost	130				154				18			24
	Interest cost	558				468				32			31
	Plan participants’ contributions	28				29				—			—
	Collections(1)	—				—				93			79
	Amendments	2				4				—			—
	Actuarial loss (gain)	722				(549		)		(21		)	(163		)
	Net transfers from variable fund/401(k) plan	13				4				—			—
	Expenses paid	(6		)		(6		)		—			—
	Benefits paid	(653		)		(628		)		(126		)	(126		)
	Benefit obligation at end of year	12,265				11,471				652			656
	Change in plan assets
	Fair value of net plan assets at beginning of year	7,221				7,029				—			—
	Actual return on plan assets	648				787				—			—
	Plan participants’ contributions	28				29				—			—
	Collections(1)	—				—				93			79
	Net transfers from variable fund/401(k) plan	13				4				—			—
	Employer contributions(2)	256				6				33			47
	Expenses paid	(6		)		(6		)		—			—
	Benefits paid	(653		)		(628		)		(126		)	(126		)
	Fair value of net plan assets at end of year	7,507				7,221				—			—
	Funded status	$	(4,758	)		$	(4,250	)		$	(652	)	$	(656	)
Amounts Recognized on TVA's Consolidated Balance Sheets	'
	Amounts related to these benefit plans recognized on TVA's consolidated balance sheets consist of regulatory assets that have not been recognized as components of net periodic benefit cost at September 30, 2014 and 2013, and the funded status of TVA’s benefit plans, which are included in Accounts payable and accrued liabilities and Post-retirement and post-employment benefit obligations:
	Amounts Recognized on TVA's Consolidated Balance Sheets
	At September 30
		Pension Benefits								Other Post-Retirement Benefits
		2014				2013				2014			2013
	Regulatory assets	$	4,157			$	3,910			$	140		$	166
	Accounts payable and accrued liabilities	(5		)		(5		)		(38		)	(39		)
	Pension and post-retirement benefit obligations(1)	(4,753		)		(4,245		)		(614		)	(617		)
	Note
	(1) Table above excludes $472 million and $486 million of post-employment benefit costs that are recorded in Post-retirement and post-employment benefit obligations on the Consolidated Balance Sheets at September 30, 2014 and 2013, respectively.
Postretirement Benefit Costs Deferred as Regulatory Assets	'
	Unrecognized amounts included in regulatory assets yet to be recognized as components of accrued benefit cost at September 30 consisted of:
	Post-retirement Benefit Costs Deferred as Regulatory Assets
	At September 30
		Pension Benefits								Other Post-Retirement Benefits
		2014				2013				2014			2013
	Unrecognized prior service cost (credit)	$	(180	)		$	(203	)		$	(39	)	$	(45	)
	Unrecognized net loss	4,337				4,113				179			211
	Total regulatory assets	$	4,157			$	3,910			$	140		$	166
Projected Benefit Obligations and Accumulated Benefit Obligations in Excess of Plan Assets	'
	The projected benefit obligation, accumulated benefit obligation, and fair value of plan assets for the pension plan at September 30, 2014, and 2013, were as follows:
	Projected Benefit Obligations and Accumulated Benefit Obligations in Excess of Plan Assets
	At September 30
		2014				2013
	Projected benefit obligation	$	12,265			$	11,471
	Accumulated benefit obligation	12,039				11,216
	Fair value of net plan assets	7,507				7,221
Components of Net Periodic Benefit Cost	'
	The components of net periodic benefit cost and other amounts recognized as changes in regulatory assets for the years ended September 30, 2014, and 2013, were as follows:
	Components of Net Periodic Benefit Cost
	For the years ended September 30
		Pension Benefits											Other Post-Retirement Benefits
		2014				2013				2012			2014			2013			2012
	Service cost	$	130			$	154			$	139		$	18		$	24		$	19
	Interest cost	558				468				490			32			31			35
	Expected return on plan assets	(435		)		(428		)		(437		)	—			—			—
	Amortization of prior service credit	(21		)		(22		)		(23		)	(6		)	(6		)	(6		)
	Recognized net actuarial loss	285				377				361			11			25			29
	Total net periodic benefit cost recognized	$	517			$	549			$	530		$	55		$	74		$	77
Expected Amortization of Regulatory Assets in Next Fiscal Year	'
	The amounts in the regulatory asset that are expected to be recognized as components of net periodic benefit cost during the next fiscal year are as follows:
	Expected Amortization of Regulatory Assets in 2015
	At September 30, 2014
		Pension Benefits				Other Post-Retirement				Total
						Benefits
	Prior service cost (credit)	$	(21	)		$	(6	)		$	(27	)
	Net actuarial loss	277				8				285
Actuarial Assumptions	'
	TVA’s reported costs of providing the plan benefits are impacted by numerous factors including the provisions of the plans, changing employee demographics, and various assumptions, the most significant of which are noted below.
	Actuarial Assumptions
	At September 30
		Pension Benefits						Other Post-Retirement Benefits
		2014			2013			2014			2013
	Assumptions utilized to determine benefit obligations at September 30
	Discount rate	4.45	%		5	%		4.5	%		5.05	%
	Rate of compensation increase	5.7	%		5.72	%		N/A			N/A
	Initial health care cost trend rate	N/A			N/A			7.5	%		8	%
	Ultimate health care cost trend rate	N/A			N/A			5	%		5	%
	Ultimate trend rate is reached in year beginning	N/A			N/A			2019			2019
	Assumptions utilized to determine net periodic benefit cost for the years ended September 30
	Discount rate	5	%		4	%		5.05	%		4	%
	Expected return on plan assets	7.25	%		7.25	%		N/A			N/A
	Rate of compensation increase	5.72	%		4.44	%		N/A			N/A
	Initial health care cost trend rate	N/A			N/A			8	%		8.5	%
	Ultimate health care cost trend rate	N/A			N/A			5	%		5	%
	Ultimate trend rate is reached in year beginning	N/A			N/A			2019			2019
Sensitivity to Certain Changes in Pension Assumptions	'
	The following chart reflects the sensitivity of pension cost to changes in certain actuarial assumptions:
	Sensitivity to Certain Changes in Pension Assumptions
	At September 30, 2014
			Change in Assumption			Impact on 2014 Pension Cost				Impact on 2014 Projected Benefit Obligation
	Actuarial Assumption
	Discount rate		(0.25	)		$	18			$	369
	Rate of return on plan assets		(0.25	)		15				N/A
Sensitivity to Changes in Assumed Health Care Cost Trend Rates	'
	The following chart reflects the sensitivity of post-retirement benefit cost to changes in the health care trend rate:
	Sensitivity to Changes in Assumed Health Care Cost Trend Rates
	At September 30, 2014
		1% Increase				1% Decrease
	Effect on total of service and interest cost components for the year	$	7			$	(7	)
	Effect on end-of-year accumulated post-retirement benefit obligation	89				(93		)
Asset Holdings and Fair Value Measurements	'
	Asset Holdings of TVARS
	At September 30
						Plan Assets at September 30
	Asset Category		Target Allocation			2014			2013
	Global equity		32	%		43	%		48	%
	Private equity		10	%		5	%		6	%
	Low volatility global public equity		5	%		1	%		—	%
	Cash		2	%		2	%		2	%
	Core fixed income		5	%		5	%		5	%
	Long-term core fixed income		5	%		5	%		4	%
	Investment grade credit		6	%		6	%		6	%
	International emerging markets fixed income		5	%		5	%		—	%
	High yield fixed income		5	%		6	%		10	%
	Global TIPS		5	%		5	%		7	%
	Private real assets		10	%		7	%		7	%
	Commodities		5	%		4	%		—	%
	MLPs		5	%		6	%		5	%
	Total		100	%		100	%		100	%
	Fair Value Measurements
	The following table provides the fair value measurement amounts for assets held by TVARS at September 30, 2014:
	TVA Retirement System
	At September 30, 2014
		Total(1) (2)				Quoted Prices in Active Markets for Identical				Significant Other			Significant
						Assets/Liabilities				Observable Inputs			Unobservable
						(Level 1)				(Level 2)			Inputs
													(Level 3)
	Assets
	Equity securities	$	1,669			$	1,668			$	—		$	1
	Preferred securities	37				5				32			—
	Debt securities
	Corporate debt securities	1,326				—				1,304			22
	Residential mortgage-backed securities	204				—				201			3
	Debt securities issued by U.S. Treasury and other U.S. government agencies	93				93				—			—
	Debt securities issued by foreign governments	225				—				218			7
	Asset-backed securities	176				—				147			29
	Debt securities issued by state/local governments	30				—				29			1
	Commercial mortgage-backed securities	23				—				20			3
	Commingled Funds
	Equity	1,106				—				1,106			—
	Debt	661				—				661			—
	Commodity	332				—				332			—
	Blended	228				—				228			—
	Institutional mutual funds	28				28				—			—
	Cash equivalents and other short-term investments	464				—				464			—
	Certificates of deposit	19				—				19			—
	Private equity funds	481				—				—			481
	Private real estate funds	435				—				334			101
	Treasury bills, U.S. Government notes, and securities held as futures and other derivative collateral	35				10				25			—
	Securities lending commingled funds	2				—				2			—
	Derivatives
	Purchased options	18				—				18			—
	Foreign currency forward receivable	8				—				8			—
	Total Assets	$	7,600			$	1,804			$	5,148		$	648
	Liabilities
	Derivatives
	Futures	11				$	11			$	—		$	—
	Foreign currency forward payable	8				—				8			—
	Written option obligations	7				—				7			—
	Total Liabilities	$	26			$	11			$	15		$	—
	Notes
	(1) Excludes approximately $65 million in net payables associated with security purchases and sales and various other payables.
	(2) Excludes a $2 million payable for collateral on loaned securities in connection with TVARS’s participation in securities lending programs.
	The following table provides the fair value measurement amounts for assets held by TVARS at September 30, 2013:
TVA Retirement System
At September 30, 2013
	Total(1) (2)				Quoted Prices in Active Markets for Identical				Significant Other			Significant
					Assets/Liabilities				Observable Inputs			Unobservable
					(Level 1)				(Level 2)			Inputs
												(Level 3)
Assets
Equity securities	$	1,689			$	1,686			$	—		$	3
Preferred securities	22				17				—			5
Debt securities
Corporate debt securities	1,352				—				1,334			18
Residential mortgage-backed securities	355				—				352			3
Debt securities issued by U.S. Treasury and other U.S. government agencies	113				113				—			—
Debt securities issued by foreign governments	31				—				30			1
Asset-backed securities	120				—				110			10
Debt securities issued by state/local governments	36				—				36			—
Commercial mortgage-backed securities	21				—				18			3
Commingled Funds
Equity	1,182				—				1,182			—
Debt	786				—				786			—
Blended	263				—				263			—
Institutional mutual funds	26				26				—			—
Cash equivalents and other short-term investments	395				1				394			—
Private equity funds	528				—				—			528
Private real estate funds	382				—				297			85
Treasury bills, U.S. Government notes, and securities held as futures and other derivative collateral	39				8				31			—
Securities lending commingled funds	3				—				3			—
Derivatives
Foreign currency forward receivable	6				—				6			—
Purchased options	6				—				6			—
Credit default swaps	4				—				4			—
Written option obligations	4				4				—			—
Total Assets	$	7,363			$	1,855			$	4,852		$	656
Liabilities
Derivatives
Foreign currency forward payable	$	6			$	—			$	6		$	—
Credit default swaps	1				—				1			—
Written option obligations	1				—				1			—
Total Liabilities	$	8			$	—			$	8		$	—
Notes
(1) Excludes approximately $131 million in net payables associated with security purchases and sales and various other payables.
(2) Excludes a $3 million payable for collateral on loaned securities in connection with TVARS’s participation in securities lending programs.
Fair Value Measurements Using Significant Unobservable Inputs	'
	The following table provides a reconciliation of beginning and ending balances of pension plan assets measured at fair value on a recurring basis where the determination of fair value includes significant unobservable inputs (Level 3):
	Fair Value Measurements Using Significant Unobservable Inputs
		Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
	Balance at October 1, 2012	$	633
	Net realized/unrealized gains (losses)	45
	Purchases, sales, issuances, and settlements (net)	(21		)
	Transfers in and/or out of Level 3	(1		)
	Balance at September 30, 2013	656
	Net realized/unrealized gains (losses)	50
	Purchases, sales, issuances, and settlements (net)	(53		)
	Transfers in and/or out of Level 3	(5		)
	Balance at September 30, 2014	$	648
Estimated Future Benefit Payments	'
	The following table sets forth the estimated future benefit payments under the benefit plans.
	Estimated Future Benefits Payments
	At September 30, 2014
						Other Post-Retirement Benefits
		Pension
		Benefits
	2015	$	712			$	39
	2016	715				40
	2017	720				41
	2018	724				41
	2019	731				41
	2020 - 2024	3,759				186

Commitments_and_Contingencies_

Commitments and Contingencies Commitments and Contingencies (Tables)	12 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	At September 30, 2014, the amounts of contractual cash commitments maturing in each of the next five years and beyond are shown below:
	Commitments and Contingencies
	Payments due in the years ending September 30
		2015		2016		2017		2018		2019		Thereafter		Total
	Debt(1)	$	1,628	$	32	$	1,555	$	1,682	$	1,032	$	17,692	$	23,621
	Debt of VIEs	32		33		35		36		38		1,137		1,311
	Membership interests of variable interest entity subject to mandatory redemption	2		2		2		2		2		29		39
	Lease obligations
	Capital	13		13		13		13		12		167		231
	Non-cancelable operating	38		36		34		27		25		63		223
	Purchase obligations
	Power	220		222		232		235		239		3,364		4,512
	Fuel	1,335		862		477		552		492		1,579		5,297
	Other	304		215		202		199		192		1,640		2,752
	Unfunded loan commitments	13		—		—		—		—		—		13
	Payments on other financings	104		104		104		104		96		305		817
	Total	$	3,689	$	1,519	$	2,654	$	2,850	$	2,128	$	25,976	$	38,816
	Note
	(1) Does not include noncash items of foreign currency exchange loss of $44 million and net discount on sale of Bonds of $89 million.
Energy Prepayment Obligations	'
	Energy Prepayment Obligations
	Payments due in the years ending September 30
		2015		2016		2017		2018		2019		Thereafter		Total
	Energy Prepayment Obligations	$	100	$	100	$	100	$	100	$	10	$	—	$	410

Related_Parties_Related_Partie

Related Parties Related Parties (Tables)	12 Months Ended
	Sep. 30, 2014
Related Party Transactions [Abstract]	'
Related Party Transactions	'
	Transactions with agencies of the federal government were as follows:
	Related Party Transactions
	For the years ended, or at, September 30
		2014		2013		2012
	Revenue from sales of electricity	$	128	$	120	$	117
	Other income	137		102		164
	Operating and maintenance	286		314		375
	Cash and cash equivalents	35		38		32
	Accounts receivable, net	85		58		49
	Accounts payable and accrued liabilities	146		133		204
	Long-term power bonds, net	3		—		—
	Return on Power Program Appropriation Investment	4		7		7
	Return of Power Program Appropriation Investment	10		20		20

Unaudited_Quarterly_Financial_1

Unaudited Quarterly Financial Information Unaudited Quarterly Financial Information (Tables)	12 Months Ended
	Sep. 30, 2014
Quarterly Financial Information Disclosure [Abstract]	'
Unaudited Quarterly Financial Information	'
	Unaudited Quarterly Financial Information
	2014
		First			Second		Third			Fourth		Total
	Operating revenues	$	2,382		$	2,938	$	2,651		$	3,166	$	11,137
	Operating expenses	2,164			2,362		2,453			2,569		9,548
	Operating income	218			576		198			597		1,589
	Net income (loss)	(67		)	295		(81		)	322		469
	Unaudited Quarterly Financial Information
	2013
		First			Second		Third			Fourth		Total
	Operating revenues	$	2,579		$	2,741	$	2,602		$	3,034	$	10,956
	Operating expenses	2,523			2,380		2,324			2,276		9,503
	Operating income	56			361		278			758		1,453
	Net income (loss)	(245		)	54		(12		)	474		271

Summary_of_Significant_Account3

Summary of Significant Accounting Policies Summary of Significant Accounting Policies - General (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
	Customers
	People
Population of Service Area	'
Number of customers for whom unbilled revenues are estimated	6
Population of TVA's service area (number of people)	9,000,000
Possible amount of future payments to the Department of Energy under the blended low-enriched uranium program	$160
Estimated future payments attributable to blended low-enriched uranium fuel currently in use	101
Maximum original maturity	'3 months
Recorded cost for emission allowances granted by the Environmental Protection Agency	0
BLEU fuel obligation	$16

Summary_of_Significant_Account4

Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Reclassificatons (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Reclassifications	'	'
Reclassification from Environmental cleanup costs-Kingston ash spill to Insurance recoveries	$47	$5

Summary_of_Significant_Account5

Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Allowance for Uncollectible Accounts (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Allowance for Uncollectible Accounts	'	'	'	'
Period of time for customers to fulfill payment arrangements	'90 days	'	'	'
Loans receivable	$92	$73	'	'
Allowance for uncollectible accounts - receivables	1	1	7	1
Additions charged to expense - receivables	1	0	6	'
Deductions - receivables	-1	-6	0	'
Allowance for uncollectible accounts - loans	9	10	12	11
Additions charged to expense - loans	0	0	1	'
Deductions - loans	-1	-2	0	'
Total allowances deducted from assets	10	11	19	12
Total additions	1	0	7	'
Total deductions	($2)	($8)	$0	'

Summary_of_Significant_Account6

Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Property, Plant, and Equipment, and Depreciation (Details) (USD $)

12 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Jun. 30, 2011

Nuclear

Nuclear

Nuclear

Coal-Fired

Coal-Fired

Coal-Fired

Hydroelectric

Hydroelectric

Hydroelectric

Gas and Oil-Fired

Gas and Oil-Fired

Gas and Oil-Fired

Transmission

Transmission

Transmission

Other

Other

Other

Electricity Generation Plant, Non-Nuclear

Electricity Generation Plant, Non-Nuclear

Fuel Fabrication and Blending Facilities

Fuel Fabrication and Blending Facilities

Environmental Agreements

Units

Property, Plant, and Equipment, and Depreciation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Depreciation

$1,600,000,000

$1,400,000,000

$1,700,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Composite depreciation rate for completed plant

3.42%

3.12%

3.78%

2.90%

2.86%

2.71%

4.37%

3.47%

5.65%

1.44%

1.30%

1.35%

3.23%

3.21%

3.67%

2.76%

2.76%

2.99%

8.40%

8.14%

8.10%

'

'

'

'

'

Number of units to be idled

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

18

Accelerated depreciation

206,000,000

49,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital leases

102,000,000

47,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

102,000,000

42,000,000

0

5,000,000

'

Allowance for funds used during construction and nuclear fuel expenditures

175,000,000

168,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

AFUDC minimum total project cost

1,000,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Minimum construction period.

'3 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Accumulated balance of qualifying projects

3,300,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capitalized software amortization period

'5 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unamortized computer software costs

22,000,000

5,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amortization expense of capitalized computer software costs

$31,000,000

$31,000,000

$31,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Summary_of_Significant_Account7

Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Energy Prepayment Obligations and Discounts on Sales (Details) (USD $)

12 Months Ended

24 Months Ended

12 Months Ended

120 Months Ended

12 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2004

Sep. 30, 2004

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

DEU [Member]

MLGW

MLGW

MLGW

MLGW

Total

Total

Total

Energy Prepayment Obligations and Discounts on Sales

'

'

'

'

'

'

'

'

'

'

'

'

'

Incremental amount of discounted energy units

$1,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Discount per kilowatt-hour

0.025

'

'

'

'

'

'

'

'

'

'

'

'

Discounted energy units contract period 1

'5 years

'

'

'

'

'

'

'

'

'

'

'

'

Discounted energy units contract period 2

'10 years

'

'

'

'

'

'

'

'

'

'

'

'

Discounted energy units contract period 3

'15 years

'

'

'

'

'

'

'

'

'

'

'

'

Discounted energy units contract period 4

'20 years

'

'

'

'

'

'

'

'

'

'

'

'

Total sales through DEU program since inception

'

'

'

'

55,000,000

'

'

'

'

'

'

'

'

Deferred Revenue

'

'

'

'

'

0

'

'

'

'

'

'

'

Deferred revenue, revenue recognized

1,000,000

2,000,000

5,000,000

'

'

'

100,000,000

100,000,000

100,000,000

1,100,000,000

'

'

'

Discounts reducing electricity sales

'

'

'

'

'

'

'

'

'

'

46,000,000

47,000,000

47,000,000

MLGW prepayment

'

'

'

1,500,000,000

'

'

'

'

'

'

'

'

'

MLGW prepayment period

'

'

'

'180 months

'

'

'

'

'

'

'

'

'

Deferred revenue expected recognition each year

'

'

'

'

'

'

$100,000,000

'

'

'

'

'

'

Restructuring_Details

Restructuring (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Restructuring and Related Activities [Abstract]	'	'
Expected increase (decrease) in operation and maintenance expense	($500)	'
Severance cost liability	45	0
Liabilities incurred during the period	65	'
Actual costs paid during the period	($20)	'
Approximate number of positions eliminated	2,000	'

Accounts_Receivable_Net_Accoun1

Accounts Receivable, Net Accounts Receivable, Net (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
In Millions, unless otherwise specified
Accounts Receivable, Net	'	'	'	'
Power receivables	$1,576	$1,495	'	'
Other receivables	101	73	'	'
Allowance for uncollectible accounts	-1	-1	-7	-1
Accounts receivable, net	$1,676	$1,567	'	'

Inventories_Net_Inventories_Ne1

Inventories, Net Inventories, Net (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Inventories, Net	'	'
Materials and supplies inventory	$616	$620
Fuel inventory	473	494
Emission allowance inventory	13	14
Allowance for inventory obsolescence	-46	-37
Inventories, net	$1,056	$1,091

Net_Completed_Plant_Net_Comple1

Net Completed Plant Net Completed Plant (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Completed Plant	'	'
Completed plant cost	$47,564	$47,073
Accumulated depreciation	24,589	23,157
Net completed plant	22,975	23,916
Coal-Fired	'	'
Completed Plant	'	'
Completed plant cost	14,078	13,847
Accumulated depreciation	9,065	8,429
Net completed plant	5,013	5,418
Gas and Oil-Fired	'	'
Completed Plant	'	'
Completed plant cost	3,411	3,386
Accumulated depreciation	1,094	1,008
Net completed plant	2,317	2,378
Nuclear	'	'
Completed Plant	'	'
Completed plant cost	18,489	18,725
Accumulated depreciation	9,593	9,103
Net completed plant	8,896	9,622
Transmission	'	'
Completed Plant	'	'
Completed plant cost	6,519	6,300
Accumulated depreciation	2,683	2,562
Net completed plant	3,836	3,738
Hydroelectric	'	'
Completed Plant	'	'
Completed plant cost	2,547	2,392
Accumulated depreciation	889	892
Net completed plant	1,658	1,500
Other Electrical Plant	'	'
Completed Plant	'	'
Completed plant cost	1,550	1,452
Accumulated depreciation	885	792
Net completed plant	665	660
Electric Subtotal	'	'
Completed Plant	'	'
Completed plant cost	46,594	46,102
Accumulated depreciation	24,209	22,786
Net completed plant	22,385	23,316
Multipurpose Dams	'	'
Completed Plant	'	'
Completed plant cost	928	928
Accumulated depreciation	364	356
Net completed plant	564	572
Other Stewardship	'	'
Completed Plant	'	'
Completed plant cost	42	43
Accumulated depreciation	16	15
Net completed plant	26	28
Other Subtotal	'	'
Completed Plant	'	'
Completed plant cost	970	971
Accumulated depreciation	380	371
Net completed plant	$590	$600

Other_LongTerm_Assets_Other_Lo1

Other Long-Term Assets Other Long-Term Assets (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
In Millions, unless otherwise specified			Energy Right Program	Other Noncurrent Assets [Member]	Other Noncurrent Assets [Member]	Accounts Receivable [Member]	Accounts Receivable [Member]
Other Long-Term Assets	'	'	'	'	'	'	'
EnergyRight receivables	$166	$150	'	$123	$117	$33	$33
Unamortized debt Issue cost of power bonds	'	'	'	68	75	'	'
Loans and other long-term receivables, net	92	73	'	87	73	'	'
Coal contract derivative assets	'	'	'	0	1	'	'
Prepaid capacity payments	'	'	'	58	62	'	'
Currency swap assets, net	0	28	'	0	28	'	'
Restricted cash	'	'	'	64	0	'	'
Other	'	'	'	83	89	'	'
Total other long-term assets	$483	$445	'	'	'	'	'
Number of days in default	'	'	'180 days	'	'	'	'

Regulatory_Assets_and_Liabilit2

Regulatory Assets and Liabilities Regulatory Assets and Liabilities - Table (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Regulatory Assets and Liabilities	'	'
Current regulatory assets	$481	$561
Non-current regulatory assets	8,994	9,131
Regulatory assets	9,475	9,692
Current regulatory liabilities	184	212
Non-current regulatory liabilities	0	1
Regulatory liabilities	184	213
Fuel cost adjustment tax equivalents	'	'
Regulatory Assets and Liabilities	'	'
Current regulatory liabilities	182	176
Fuel cost adjustment receivable/payable	'	'
Regulatory Assets and Liabilities	'	'
Current regulatory liabilities	0	29
Unrealized gains/losses on commodity derivatives	'	'
Regulatory Assets and Liabilities	'	'
Current regulatory liabilities	2	7
Non-current regulatory liabilities	0	1
Unrealized gains/losses on commodity derivatives	'	'
Regulatory Assets and Liabilities	'	'
Current regulatory assets	134	183
Non-current regulatory assets	72	139
Deferred nuclear generating units	'	'
Regulatory Assets and Liabilities	'	'
Current regulatory assets	237	237
Non-current regulatory assets	1,255	1,438
Regulatory assets	1,500	'
Environmental agreements	'	'
Regulatory Assets and Liabilities	'	'
Current regulatory assets	54	73
Non-current regulatory assets	108	189
Fuel cost adjustment receivable/payable	'	'
Regulatory Assets and Liabilities	'	'
Current regulatory assets	9	0
Environmental cleanup costs - Kingston ash spill	'	'
Regulatory Assets and Liabilities	'	'
Current regulatory assets	47	68
Non-current regulatory assets	421	681
Deferred pension costs and other post-retirement benefits costs	'	'
Regulatory Assets and Liabilities	'	'
Non-current regulatory assets	4,297	4,076
Unrealized losses on interest rate derivatives	'	'
Regulatory Assets and Liabilities	'	'
Non-current regulatory assets	957	808
Nuclear decommissioning costs	'	'
Regulatory Assets and Liabilities	'	'
Non-current regulatory assets	931	893
Non-nuclear decommissioning costs	'	'
Regulatory Assets and Liabilities	'	'
Non-current regulatory assets	645	571
Other non-current regulatory assets	'	'
Regulatory Assets and Liabilities	'	'
Non-current regulatory assets	$308	$336

Regulatory_Assets_and_Liabilit3

Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Details) (USD $)

12 Months Ended

30 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Jul. 31, 2005

Sep. 30, 2014

Jul. 31, 2005

Sep. 30, 2014

Sep. 30, 2010

Sep. 30, 2009

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Units

Deferred Nuclear Generating Units and Construction Costs

Deferred Nuclear Generating Units and Construction Costs

Environmental Cleanup Costs - Kingston Ash Spill

Environmental Cleanup Costs - Kingston Ash Spill

Environmental Cleanup Costs - Kingston Ash Spill

Environmental Agreements

Energy Efficiency Projects

Paid to States

Civil Penalties

Derivatives Under FTP

Derivatives Under FTP

Deferred nuclear generating units

Environmental Agreements

Environmental Agreements

Environmental Agreements

Regulatory Assets and Liabilities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net unrealized gains (losses)

'

'

'

'

'

'

'

'

'

'

'

'

'

$103,000,000

[1]

$166,000,000

[1]

'

Investment in deferred generating units

'

'

'

'

'

3,900,000,000

'

'

'

'

'

'

'

'

'

'

Number of deferred generating units

'

'

'

2

'

'

'

'

'

'

'

'

'

'

'

'

Regulatory Noncurrent Asset, Amortization Period

'

'

'

'

'P10Y

'

'

'

'

'

'

'

'

'

'

'

Remaining balance to be included in plant asset balance at completion

'

'

'

'

619,000,000

'

'

'

'

'

'

'

'

'

'

'

Regulatory Assets

9,475,000,000

9,475,000,000

9,692,000,000

'

'

'

'

'

'

'

'

'

'

'

'

1,500,000,000

Yearly amortization of Deferred nuclear generating units

237,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Initial regulatory asset

'

'

'

'

'

'

'

'

'

360,000,000

'

'

'

'

'

'

Investment in environmental agreement projects

'

'

'

'

'

'

'

'

'

290,000,000

'

'

'

'

'

'

Amount to be provided to fund environmental projects

'

'

'

'

'

'

'

'

'

60,000,000

'

'

'

'

'

'

Amount to be paid in civil penalties

'

'

'

'

'

'

'

'

'

10,000,000

'

'

'

'

'

'

Regulatory asset amount expensed

'

'

'

'

'

'

'

'

'

'

138,000,000

50,000,000

10,000,000

'

'

'

Total recorded estimate of Kingston cleanup costs

1,100,000,000

1,100,000,000

'

'

'

'

1,100,000,000

'

933,000,000

'

'

'

'

'

'

'

Kingston insurance recoveries

175,000,000

267,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Estimate increase

'

'

'

'

'

'

'

$192,000,000

'

'

'

'

'

'

'

'

Current regulatory asset amortization period

'

'

'

'

'

'

'12 months

'

'

'

'

'

'

'

'

'

[1]

Fair values of certain derivatives under the FTP that were in net liability positions totaling $69 million and $100 million at SeptemberB 30, 2014 and SeptemberB 30, 2013, respectively, are recorded in TVA's margin cash accounts in Other current assets. These derivatives are transacted with futures commission merchants, and cash deposits have been posted to the margin cash accounts held with each futures commission merchant to offset the net liability positions in full.

Variable_Interest_Entities_Var2

Variable Interest Entities Variable Interest Entities (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Aug. 09, 2013	Jan. 17, 2012
VIE Financing	'	'	'	'	'
Membership interests of VIE subject to mandatory redemption	$50	$50	'	$40	'
Total liabilities	1,362	1,393	'	'	1,000
Interest expense	64	50	34	'	'
SCCG	'	'	'	'	'
VIE Financing	'	'	'	'	'
Face Amount	'	'	'	360	'
JSCCG	'	'	'	'	'
VIE Financing	'	'	'	'	'
Face Amount	'	'	'	'	900
Holdco	'	'	'	'	'
VIE Financing	'	'	'	'	'
Face Amount	'	'	'	'	100
Accrued interest of VIE	'	'	'	'	'
VIE Financing	'	'	'	'	'
Total liabilities	12	12	'	'	'
Current portion of membership interests of VIE subject to mandatory redemption	'	'	'	'	'
VIE Financing	'	'	'	'	'
Total liabilities	2	2	'	'	'
Current maturities of long-term debt of VIE	'	'	'	'	'
VIE Financing	'	'	'	'	'
Total liabilities	32	30	'	'	'
Total current liabilities of VIE	'	'	'	'	'
VIE Financing	'	'	'	'	'
Total liabilities	46	44	'	'	'
Membership interests of VIE subject to mandatory redemption	'	'	'	'	'
VIE Financing	'	'	'	'	'
Total liabilities	37	38	'	'	'
Long-term debt of VIE	'	'	'	'	'
VIE Financing	'	'	'	'	'
Total liabilities	$1,279	$1,311	'	'	'

Kingston_Fossil_Plant_Ash_Spil2

Kingston Fossil Plant Ash Spill Kingston Fossil Plant Ash Spill (Details) (USD $)	12 Months Ended	30 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2008
			Dredge_cells
			Cubic_yards
Kingston Fossil Plant Ash Spill	'	'	'
Number of dredge cells that failed	'	'	1
Cubic yards of water and coal fly ash that flowed out of the cell	'	'	5,000,000
Total recorded estimate of Kingston cleanup costs	$1,100,000,000	$1,100,000,000	'
Period collected in rates	'15 years	'	'
Kingston cleanup amounts spent to date	1,100,000,000	1,100,000,000	'
Remaining estimated Kingston liability	21,000,000	21,000,000	'
Kingston insurance recoveries	$175,000,000	$267,000,000	'

Other_LongTerm_Liabilities_Oth1

Other Long-Term Liabilities Other Long-Term Liabilities (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013	Aug. 09, 2013	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
In Millions, unless otherwise specified				Energy Right Program	Other long-term liabilities	Other long-term liabilities	Accounts payable and accrued liabilities	Accounts payable and accrued liabilities
Other Long-Term Liabilities	'	'	'	'	'	'	'	'
Number of days in default	'	'	'	'180 days	'	'	'	'
Interest rate swap liabilities	$1,348	$1,199	'	'	$1,348	$1,199	'	'
Environmental agreements liability	'	'	'	'	108	190	'	'
EnergyRight financing obligation	215	222	'	'	152	149	38	37
Membership interests of VIE subject to mandatory redemption	'	'	'	'	37	38	'	'
Commodity contract derivative liabilities	'	'	'	'	17	35	'	'
Commodity swap derivative liabilities	'	'	'	'	14	36	'	'
Currency swap liabilities	15	15	'	'	15	15	'	'
Other	'	'	'	'	271	199	'	'
Total other long-term liabilities	1,962	1,861	'	'	'	'	'	'
Percentage of membership interests issued	'	'	100.00%	'	'	'	'	'
Membership interests of VIE subject to mandatory redemption	50	50	40	'	'	'	'	'
SCCG balloon payment	'	'	4	'	'	'	'	'
Membership interests of VIE subject to mandatory redemption, interest rate, stated percentage	'	'	7.00%	'	'	'	'	'
Membership interests of VIE subject to mandatory redemption, amount, current	$2	$2	'	'	'	'	'	'

Asset_Retirement_Obligations_A2

Asset Retirement Obligations Asset Retirement Obligations (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013
Asset Retirement Obligations	'		'
Increase in ARO liability	($319)		'
Initial decommissioning estimate for nuclear	'7 years		'
ARO-Nuclear Decommissioning Study Update	'5 years		'
Accretion expense	40		'
Balance	3,488	[1]	3,289	[1]
Settlements (ash storage areas)	-14	[1]	-37	[1]
Asset Retirement Obligation, Revision of Estimate (Site Specific Studies)	-472	[1]	'
Change in estimate	-10	[1]	-66	[1]
Accretion (recorded as regulatory asset)	177	[1]	170	[1]
Balance	3,169	[1]	3,488	[1]
Current portion of ARO	80		'
Nuclear	'		'
Asset Retirement Obligations	'		'
Balance	2,399	[1]	2,208	[1]
Settlements (ash storage areas)	0	[1]	0	[1]
Asset Retirement Obligation, Revision of Estimate (Site Specific Studies)	-472	[1]	'
Change in estimate	0	[1]	-66	[1]
Accretion (recorded as regulatory asset)	125	[1]	125	[1]
Balance	2,052	[1]	2,399	[1]
Non-nuclear	'		'
Asset Retirement Obligations	'		'
Balance	1,089	[1]	1,081	[1]
Settlements (ash storage areas)	-14	[1]	-37	[1]
Asset Retirement Obligation, Revision of Estimate (Site Specific Studies)	0	[1]	'
Change in estimate	-10	[1]	0	[1]
Accretion (recorded as regulatory asset)	52	[1]	45	[1]
Balance	$1,117	[1]	$1,089	[1]
[1]	The current portion of ARO in the amount of $80 million is included in Accounts payable and accrued liabilities.

Debt_and_Other_Obligations_Deb1

Debt and Other Obligations Debt and Other Obligations - General (Details) (USD $)	12 Months Ended
In Billions, unless otherwise specified	Sep. 30, 2014
	tests
	Types_of_bonds
Debt Instrument	'
Debt ceiling	$30
Number of types of bonds outstanding	2
Power bonds years to maturity - low end of range	'1 year
Power bonds years to maturity - high end of range	'50 years
Discount notes years to maturity - high end of range	'1 year
Number of bond tests	2
Time period for meeting the bondholder protection test	'5 years

Debt_and_Other_Obligations_Deb2

Debt and Other Obligations Debt and Other Obligations - Secured Debt of VIEs (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013	Aug. 09, 2013	Aug. 09, 2013	Jan. 17, 2012	Jan. 17, 2012
In Millions, unless otherwise specified				SCCG	JSCCG	Holdco
Debt Instrument	'	'	'	'	'	'
Face Amount	'	'	'	$360	$900	$100
Membership interests of VIE subject to mandatory redemption	50	50	40	'	'	'
Interest rate	'	'	'	3.85%	4.63%	7.10%
Holdco balloon payment upon maturity	'	'	'	'	'	10
Long-term debt of variable interest entities (including current maturities)	$1,425	$1,386	'	'	'	'

Debt_and_Other_Obligations_Deb3

Debt and Other Obligations Debt and Other Obligations - Short-Term Debt (Details) (USD $)	12 Months Ended
In Billions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Short-term Debt	'	'	'
Short-term debt, weighted average interest rate	'	0.04%	0.09%
Short-term debt, maximum amount outstanding during period	$2.40	$3.40	$3.20
Short-term debt, average amount outstanding	$1.70	$1.90	$1.10
Weighted average interest rates during period	0.05%	0.08%	0.08%

Debt_and_Other_Obligations_Deb4

Debt and Other Obligations Debt and Other Obligations - Put and Call Options (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
	Bond_issues
	PARRS_issues
Debt Instrument	'
Amount of redeemable bond issues outstanding	$515
Call price	100.00%
Bond issues with survivor's option	15
Bonds outstanding with survivor's option	375
Number of issues of Putable Automatic Rate Reset Securities outstanding	2
Fixed-rate period for coupon rate reset on PARRS	'5 years
Average time period	'5 days
PARRS 1998 Series D Bond	'
Debt Instrument	'
Amount of redeemable bond issues outstanding	324
Debt Instrument, Basis Point Spread on Variable Rate	94
Number of rate resets	6
PARRS interest rate prior to rate reset	6.75%
PARRS interest rate after rate reset	3.83%
Amount of bonds redeemed	251
PARRS 1999 Series A Bond	'
Debt Instrument	'
Amount of redeemable bond issues outstanding	270
Debt Instrument, Basis Point Spread on Variable Rate	84
Number of rate resets	5
PARRS interest rate prior to rate reset	6.50%
PARRS interest rate after rate reset	3.96%
Amount of bonds redeemed	$255

Debt_and_Other_Obligations_Deb5

Debt and Other Obligations Debt and Other Obligations - Debt Securities Activity (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2012
Debt Instrument	'		'		'
Issues of variable interest entities	$0		$360		$1,000
Issues of power bonds	989		2,122		1,126
Amount	395		2,371		'
Redemptions/Maturities of variable interest entities	30		13		6
Redemptions/Maturities of power bonds	365		2,358		2,717
Discount on debt issues	-11		-30		'
Debt of variable interest entities	'		'		'
Debt Instrument	'		'		'
Redemptions/Maturities of variable interest entities	30	[1]	13	[1]	'
Electronotes	'		'		'
Debt Instrument	'		'		'
Redemptions/Maturities of power bonds	335	[1]	50	[1]	'
1998 Series C	'		'		'
Debt Instrument	'		'		'
Redemptions/Maturities of power bonds	0	[1]	1,359	[1]	'
1998 Series D	'		'		'
Debt Instrument	'		'		'
Redemptions/Maturities of power bonds	0	[1]	2	[1]	'
1999 Series A	'		'		'
Debt Instrument	'		'		'
Redemptions/Maturities of power bonds	0	[1]	1	[1]	'
2003 Series C	'		'		'
Debt Instrument	'		'		'
Redemptions/Maturities of power bonds	0	[1]	940	[1]	'
2009 Series A	'		'		'
Debt Instrument	'		'		'
Redemptions/Maturities of power bonds	4	[1]	4	[1]	'
2009 Series B	'		'		'
Debt Instrument	'		'		'
Redemptions/Maturities of power bonds	26	[1]	2	[1]	'
2013 Series A	'		'		'
Debt Instrument	'		'		'
Percent of par value	'		99.52%		'
2014 Series A	'		'		'
Debt Instrument	'		'		'
Percent of par value	98.94%		'		'
Total	'		'		'
Debt Instrument	'		'		'
Percent of par value	100.00%		'		'
Debt of variable interest entities	'		'		'
Debt Instrument	'		'		'
Issues of variable interest entities	0		360		'
Electronotes	'		'		'
Debt Instrument	'		'		'
Issues of power bonds	0		152		'
2012 Series B	'		'		'
Debt Instrument	'		'		'
Issues of power bonds	0		1,000	[2]	'
Percent of par value	'		97.49%		'
2013 Series A	'		'		'
Debt Instrument	'		'		'
Issues of power bonds	0		1,000	[3]	'
2014 Series A	'		'		'
Debt Instrument	'		'		'
Issues of power bonds	1,000	[4]	0		'
Total	'		'		'
Debt Instrument	'		'		'
Amount	$989		$2,482		'
[1]	All redemptions were at 100 percent of par.
[2]	The 2012 Series B bonds were issued at 97.49 percent of par.
[3]	The 2013 Series A bonds were issued at 99.52 percent of par.
[4]	The 2014 Series A bonds were issued at 98.94 percent of par.

Debt_and_Other_Obligations_Deb6

Debt and Other Obligations Debt and Other Obligations - Debt Outstanding (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013
	Electronotes
Short-term debt	'		'
Short-term debt, net of discounts	$596		$2,432
Current maturities of long-term debt of variable interest entities	32		30
Current maturities of power bonds	1,032		32
Total current debt outstanding, net	1,660		2,494
Long-term debt	'		'
Unamortized discount, premiums and other	-89		-85
Long-term debt of variable interest entities	1,279		1,311
Total long-term debt, net	23,227		23,626
Long-term power bonds	22,037	[1]	22,400	[1]
Long-term Debt, net	21,948		22,315
Current maturities of power bonds	1,032		32
Foreign currency exchange loss	44		43
Number of issues with partial maturities	1		'
Electronotes	'		'
Long-term debt	'		'
Long-term Debt, net	387	[2]	723	[2]
Maturity date - earliest	15-May-20		'
Maturity date - latest	15-Feb-43		'
Coupon rate - minimum	2.38%		'
Coupon rate - maximum	4.38%		'
Call date - earliest	15-Feb-15		'
Call date - latest	15-Feb-18		'
880591DY5	'		'
Debt Instrument	'		'
Maturity	15-Jun-15		'
Coupon rate	4.38%		'
Long-term debt	'		'
Long-term Debt, net	0		1,000
880591EE8	'		'
Debt Instrument	'		'
Maturity	15-Nov-15		'
Coupon rate	2.25%		'
Long-term debt	'		'
Long-term Debt, net	2	[3]	4	[3]
880591DS8	'		'
Debt Instrument	'		'
Maturity	15-Dec-16		'
Coupon rate	4.88%		'
Long-term debt	'		'
Long-term Debt, net	524		524
880591EA6	'		'
Debt Instrument	'		'
Maturity	18-Jul-17		'
Coupon rate	5.50%		'
Long-term debt	'		'
Long-term Debt, net	1,000		1,000
880591CU4	'		'
Debt Instrument	'		'
Maturity	15-Dec-17		'
Coupon rate	6.25%		'
Long-term debt	'		'
Long-term Debt, net	650		650
880591EC2	'		'
Debt Instrument	'		'
Maturity	1-Apr-18		'
Coupon rate	4.50%		'
Long-term debt	'		'
Long-term Debt, net	1,000		1,000
880591EQ1	'		'
Debt Instrument	'		'
Maturity	15-Oct-18		'
Coupon rate	1.75%		'
Long-term debt	'		'
Long-term Debt, net	1,000		1,000
880591EL2	'		'
Debt Instrument	'		'
Maturity	15-Feb-21		'
Coupon rate	3.88%		'
Long-term debt	'		'
Long-term Debt, net	1,500		1,500
880591DC3	'		'
Debt Instrument	'		'
Maturity	7-Jun-21		'
Coupon rate	5.81%		'
Long-term debt	'		'
Long-term Debt, net	324	[4]	324	[4]
880591EN8	'		'
Debt Instrument	'		'
Maturity	15-Aug-22		'
Coupon rate	1.88%		'
Long-term debt	'		'
Long-term Debt, net	1,000		1,000
880591ER9	'		'
Debt Instrument	'		'
Maturity	15-Sep-24		'
Coupon rate	2.88%		'
Long-term debt	'		'
Long-term Debt, net	1,000		0
880591CJ9	'		'
Debt Instrument	'		'
Maturity	1-Nov-25		'
Coupon rate	6.75%		'
Long-term debt	'		'
Long-term Debt, net	1,350		1,350
880591300	'		'
Debt Instrument	'		'
Maturity	1-Jun-28		'
Coupon rate	3.83%		'
Long-term debt	'		'
Long-term Debt, net	324	[5]	324	[5]
880591409	'		'
Debt Instrument	'		'
Maturity	1-May-29		'
Coupon rate	3.96%		'
Long-term debt	'		'
Long-term Debt, net	270	[5]	270	[5]
880591DM1	'		'
Debt Instrument	'		'
Maturity	1-May-30		'
Coupon rate	7.13%		'
Long-term debt	'		'
Long-term Debt, net	1,000		1,000
880591DP4	'		'
Debt Instrument	'		'
Maturity	7-Jun-32		'
Coupon rate	6.59%		'
Long-term debt	'		'
Long-term Debt, net	406	[4]	405	[4]
880591DV1	'		'
Debt Instrument	'		'
Maturity	15-Jul-33		'
Coupon rate	4.70%		'
Long-term debt	'		'
Long-term Debt, net	472		472
880591EF5	'		'
Debt Instrument	'		'
Maturity	15-Jun-34		'
Coupon rate	3.77%		'
Long-term debt	'		'
Long-term Debt, net	388	[3]	414	[3]
880591DX7	'		'
Debt Instrument	'		'
Maturity	15-Jun-35		'
Coupon rate	4.65%		'
Long-term debt	'		'
Long-term Debt, net	436		436
880591CK6	'		'
Debt Instrument	'		'
Maturity	1-Apr-36		'
Coupon rate	5.98%		'
Long-term debt	'		'
Long-term Debt, net	121		121
880591CS9	'		'
Debt Instrument	'		'
Maturity	1-Apr-36		'
Coupon rate	5.88%		'
Long-term debt	'		'
Long-term Debt, net	1,500		1,500
880591CP5	'		'
Debt Instrument	'		'
Maturity	15-Jan-38		'
Coupon rate	6.15%		'
Long-term debt	'		'
Long-term Debt, net	1,000		1,000
880591ED0	'		'
Debt Instrument	'		'
Maturity	15-Jun-38		'
Coupon rate	5.50%		'
Long-term debt	'		'
Long-term Debt, net	500		500
880591EH1	'		'
Debt Instrument	'		'
Maturity	15-Sep-39		'
Coupon rate	5.25%		'
Long-term debt	'		'
Long-term Debt, net	2,000		2,000
880591EP3	'		'
Debt Instrument	'		'
Maturity	15-Dec-42		'
Coupon rate	3.50%		'
Long-term debt	'		'
Long-term Debt, net	1,000		1,000
880591DU3	'		'
Debt Instrument	'		'
Maturity	7-Jun-43		'
Coupon rate	4.96%		'
Long-term debt	'		'
Long-term Debt, net	243	[4]	243	[4]
880591CF7	'		'
Debt Instrument	'		'
Maturity	15-Jul-45		'
Coupon rate	6.24%		'
Long-term debt	'		'
Long-term Debt, net	140		140
Call date - earliest	15-Jul-20		'
880591EB4	'		'
Debt Instrument	'		'
Maturity	15-Jan-48		'
Coupon rate	4.88%		'
Long-term debt	'		'
Long-term Debt, net	500		500
880591DZ2	'		'
Debt Instrument	'		'
Maturity	1-Apr-56		'
Coupon rate	5.38%		'
Long-term debt	'		'
Long-term Debt, net	1,000		1,000
880591EJ7	'		'
Debt Instrument	'		'
Maturity	15-Sep-60		'
Coupon rate	4.63%		'
Long-term debt	'		'
Long-term Debt, net	1,000		1,000
880591EE8	'		'
Debt Instrument	'		'
Maturity	15-Nov-14		'
Coupon rate	2.25%		'
Long-term debt	'		'
Current maturities of power bonds	3		3
880591EF5	'		'
Debt Instrument	'		'
Maturity	15-Dec-14		'
Coupon rate	3.77%		'
Long-term debt	'		'
Current maturities of power bonds	26		26
880591CW0	'		'
Debt Instrument	'		'
Maturity	15-Jun-15		'
Coupon rate	4.38%		'
Long-term debt	'		'
Current maturities of power bonds	'		0
880591DY5	'		'
Long-term debt	'		'
Current maturities of power bonds	1,000		'
88059TEL1	'		'
Debt Instrument	'		'
Maturity	15-Nov-14		'
Coupon rate	2.65%		'
Long-term debt	'		'
Current maturities of power bonds	$3		$3
[1]	Includes net exchange losses from currency transactions of $44 million at SeptemberB 30, 2014 and $43 million at SeptemberB 30, 2013.
[2]	Includes one electronotesB. issue with partial maturities of principal for each required annual payment.
[3]	These Bonds include partial maturities of principal for each required annual payment.
[4]	The coupon rate represents TVAbs effective interest rate.
[5]	TVA PARRS, CUSIP numbers 880591300 and 880591409, may be redeemed under certain conditions. See Put and Call Options.

Debt_and_Other_Obligations_Deb7

Debt and Other Obligations Debt and Other Obligations - Maturities Due (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Debt Instrument	'	'
2015	$1,064	'
2016	65	'
2017	1,590	'
2018	1,718	'
2019	1,070	'
Thereafter	18,829	'
Total	24,336	'
Foreign currency exchange loss	44	43
Unamortized discount, premiums and other	89	85
Short-term debt, net of discounts	$596	$2,432

Debt_and_Other_Obligations_Deb8

Debt and Other Obligations Debt and Other Obligations - Credit Facility Agreements (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013
Credit Facility Agreements	'	'
Current borrowing capacity	$150,000,000	'
Line of Credit	'	'
Credit Facility Agreements	'	'
Current borrowing capacity	150,000,000	'
Credit facility agreements borrowings outstanding	0	'
Amount of letters of credit outstanding	1,000,000,000	800,000,000
Revolving Credit Facilities	'	'
Credit Facility Agreements	'	'
Current borrowing capacity	2,500,000,000	'
Credit facility agreements borrowings outstanding	0	0
Number of revolving credit facilities	3	'
Revolving credit facility 1	1,000,000,000	'
Revolving credit facility 2	1,000,000,000	'
Revolving credit facility 3	$500,000,000	'

Debt_and_Other_Obligations_Deb9

Debt and Other Obligations Debt and Other Obligations - Lease/Leasebacks (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2003	Sep. 30, 2014	Sep. 30, 2013
	Units
Lease/Leasebacks [Abstract]	'	'	'
Proceeds prior to 2004	$945	'	'
Leaseback transaction, number of units	24	'	'
Proceeds in 2003	389	'	'
CT and QTE outstanding leaseback obligation	'	$691	$761

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Equity [Abstract]	'	'	'
Reclassification on cash flow hedges from AOCI to interest expense	$2	$1	$35

Risk_Management_Activities_and2

Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Derivative Instruments That Receive Hedge Accounting Treatment (Details) (USD $)	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Summary of Derivative Instruments That Receive Hedge Accounting Treatment	'	'	'
Net unrealized gain (loss) on future cash flow hedges	$4,000,000	$78,000,000	$99,000,000
Reclassification to earnings from cash flow hedges	-2,000,000	-1,000,000	-35,000,000
Ineffective portion excluded from testing	0	0	'
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred	$37,000,000	'	'

Risk_Management_Activities_and3

Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Derivative Instruments That Do Not Receive Hedge Accounting Treatment (Details) (USD $)	12 Months Ended
	Sep. 30, 2014		Sep. 30, 2013
Derivative	'		'
Change in Unrealized gains (losses) on Interest Rate Derivatives	($149,000,000)		$524,000,000
Amount of gain (loss) recognized in income on derivatives	-57,000,000		'
Unrealized gains/losses on derivatives	0		0
FTP transaction limit	130,000,000		'
Maximum hedge volume	75.00%		'
Market value limitation of outstanding construction materials hedging transactions	100,000,000		'
Portfolio value at risk limit for foreign currency transactions	5,000,000		'
Interest Rate Swap	'		'
Derivative	'		'
Amount of gain (loss) recognized in income on derivatives	0	[1]	0	[1]
Commodity Contract Derivatives	'		'
Derivative	'		'
Amount of gain (loss) recognized in income on derivatives	-64,000,000		-11,000,000
Fair value	-96,000,000		-141,000,000
Commodity Derivatives Under Financial Trading Program	'		'
Derivative	'		'
Amount of gain (loss) recognized in income on derivatives	-43,000,000		-126,000,000
Fair value	-103,000,000	[2]	-166,000,000	[2]
Coal Contract Derivatives	'		'
Derivative	'		'
Number of contracts	24		19
Notional amount	31,000,000		43,000,000
Fair value	-86,000,000		-140,000,000
Natural Gas	'		'
Derivative	'		'
Number of contracts	46		13
Notional amount	62,000,000		39,000,000
Fair value	-10,000,000		-1,000,000
Maximum | Coal Contract Derivatives	'		'
Derivative	'		'
Derivative, Term of Contract	'3 years		'
Maximum | Natural Gas	'		'
Derivative	'		'
Derivative, Term of Contract	'2 years		'
Coal Contract Derivatives	'		'
Derivative	'		'
Unrealized gains/losses on derivatives	0		0
Fair value	$0		$0
[1]	Generally, TVA maintains a level of outstanding discount notes equal to or greater than the notional amount of the interest rate swaps. However, in September 2014 TVA issued long-term Bonds in anticipation of the maturity of other long-term debt, and used the proceeds to pay down discount notes, which caused the balance of discount notes outstanding at September 30, 2014, to fall below the notional amount of the interest rate swaps. There is no impact on the statements of operations due to the use of regulatory accounting for these items.
[2]	Fair values of certain derivatives under the FTP that were in net liability positions totaling $69 million and $100 million at SeptemberB 30, 2014 and SeptemberB 30, 2013, respectively, are recorded in TVA's margin cash accounts in Other current assets. These derivatives are transacted with futures commission merchants, and cash deposits have been posted to the margin cash accounts held with each futures commission merchant to offset the net liability positions in full.

Risk_Management_Activities_and4

Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Mark-to-Market Values of TVA Derivatives (Details) (USD $)	Sep. 30, 2014		Sep. 30, 2013
In Millions, unless otherwise specified
Derivatives, Fair Value	'		'
Derivative Liability, Fair Value, Gross Liability	$1,517		$1,481
Commodity derivatives under FTP	'		'
Derivatives, Fair Value	'		'
Fair value	'		0
Commodity derivatives under FTP | Other current assets	'		'
Derivatives, Fair Value	'		'
Derivative Liability, Fair Value, Gross Liability	69		100
200 million Sterling currency swap | Other long-term liabilities	'		'
Derivatives, Fair Value	'		'
Fair value	-15		-15
250 million Sterling currency swap | Other long-term assets	'		'
Derivatives, Fair Value	'		'
Fair value	56		51
150 million Sterling currency swap | Other long-term assets	'		'
Derivatives, Fair Value	'		'
Fair value	8		10
$1.0 billion notional interest rate swap | Other long-term liabilities	'		'
Derivatives, Fair Value	'		'
Fair value	-987		-886
$476 million notional interest rate swap | Other long-term liabilities	'		'
Derivatives, Fair Value	'		'
Fair value	-349		-300
$42 million notional interest rate swap | Other long-term liabilities	'		'
Derivatives, Fair Value	'		'
Fair value	-12		-13
Commodity contract derivatives	'		'
Derivatives, Fair Value	'		'
Fair value	-96		-141
Commodity contract derivatives | Other long-term assets	'		'
Derivatives, Fair Value	'		'
Fair value	'		1
Commodity contract derivatives | Other current assets	'		'
Derivatives, Fair Value	'		'
Fair value	1		2
Commodity contract derivatives | Other long-term liabilities	'		'
Derivatives, Fair Value	'		'
Fair value	-17		-35
Commodity contract derivatives | Accounts payable and accrued liabilities	'		'
Derivatives, Fair Value	'		'
Fair value	-80		-109
Derivatives Under FTP	'		'
Derivatives, Fair Value	'		'
Fair value	-103	[1]	-166	[1]
Derivatives Under FTP | Other current assets	'		'
Derivatives, Fair Value	'		'
Fair value	-69		-97
Derivatives Under FTP | Other long-term liabilities	'		'
Derivatives, Fair Value	'		'
Fair value	-14		-36
Derivatives Under FTP | Accounts payable and accrued liabilities	'		'
Derivatives, Fair Value	'		'
Fair value	($20)		($33)
[1]	Fair values of certain derivatives under the FTP that were in net liability positions totaling $69 million and $100 million at SeptemberB 30, 2014 and SeptemberB 30, 2013, respectively, are recorded in TVA's margin cash accounts in Other current assets. These derivatives are transacted with futures commission merchants, and cash deposits have been posted to the margin cash accounts held with each futures commission merchant to offset the net liability positions in full.

Risk_Management_Activities_and5

Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Currency Swaps Outstanding (Details) (GBP £)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Derivative	'
Number of British pound sterling denominated bond transactions	3
1999 Currency Swap Contract	'
Derivative	'
Effective Date of Currency Swap Contract	'1999
Associated TVA bond issues currency exposure	£ 200
Expiration Date of Swap	'2021
Overall effective cost to TVA	5.81%
2001 Currency Swap Contract	'
Derivative	'
Effective Date of Currency Swap Contract	'2001
Associated TVA bond issues currency exposure	250
Expiration Date of Swap	'2032
Overall effective cost to TVA	6.59%
2003 Currency Swap Contract	'
Derivative	'
Effective Date of Currency Swap Contract	'2003
Associated TVA bond issues currency exposure	£ 150
Expiration Date of Swap	'2043
Overall effective cost to TVA	4.96%

Risk_Management_Activities_and6

Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Derivatives Under Financial Trading Program (Details) (USD $)	12 Months Ended
	Sep. 30, 2014		Sep. 30, 2013
Derivative	'		'
FTP transaction limit	$130,000,000		'
Unrealized gains/losses on derivatives	0		0
Natural Gas Futures	'		'
Derivative	'		'
Notional amount	0		0
Fair value	0		0
Fuel Oil/Crude Oil Futures	'		'
Derivative	'		'
Notional amount	0		0
Fair value	0		0
Natural Gas Swap	'		'
Derivative	'		'
Notional amount	102,227,500	[1]	152,922,500	[1]
Fair value	-103,000,000	[1]	-169,000,000	[1]
Fuel Oil/Crude Oil Swap	'		'
Derivative	'		'
Notional amount	0		1,205,000	[1]
Fair value	0		3,000,000	[1]
Natural Gas Option	'		'
Derivative	'		'
Notional amount	0		0
Fair value	0		0
Fuel Oil/Crude Oil Option	'		'
Derivative	'		'
Notional amount	0		0
Fair value	0		0
Natural Gas Total Contracts	'		'
Derivative	'		'
Notional amount	102,227,500	[1]	152,922,500	[1]
Unrealized gains/losses on derivatives	-103,000,000		-169,000,000
Decrease (increase) in fuel expense	-34,000,000		-78,000,000
Decrease (increase) in purchased power expense	-11,000,000		-51,000,000
Fair value	-103,000,000	[1]	-169,000,000	[1]
Fuel Oil/Crude Oil Total Contracts	'		'
Derivative	'		'
Notional amount	0		1,205,000	[1]
Unrealized gains/losses on derivatives	0		3,000,000
Decrease (increase) in fuel expense	2,000,000		4,000,000
Fair value	0		3,000,000	[1]
Coal Contract Total Contracts	'		'
Derivative	'		'
Unrealized gains/losses on derivatives	0		0
Decrease (increase) in fuel expense	0		-1,000,000
Fair value	0		0
Closed Derivative Contracts	'		'
Derivative	'		'
Fair value	($5,000,000)		($8,000,000)
Swap contracts	'		'
Derivative	'		'
Remaining terms	'3 years		'
[1]	Due to the right of setoff and method of settlement, TVA elects to record commodity derivatives under the FTP based on its net commodity position with the broker or other counterparty. Notional amounts disclosed represent the net absolute value of contractual amounts.

Risk_Management_Activities_and7

Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Collateral (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014
	Credit of Customers	Credit of Customers	Collateral
	Customers	Customers
Derivative	'	'	'
Number of customers that represent the percent of outstanding accounts receivable	3	3	'
Aggregate fair value of derivative instruments with credit-risk related contingent features that were in a liability position	'	'	$1,400,000,000
Collateral obligations	'	'	900,000,000
Collateral already posted	'	'	1,000,000,000
Likely cash collateral obligation increase if credit is downgraded	'	'	$22,000,000

Risk_Management_Activities_and8

Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Counterparty Credit Risk (Details)	Sep. 30, 2014	Sep. 30, 2013
	Customers	Customers
Derivative	'	'
Number of active future commission merchants	2	'
Credit of Customers	'	'
Derivative	'	'
Number of customers that represent the percent of outstanding accounts receivable	3	3
Percent of total outstanding accounts receivables by customers	27.00%	27.00%
Power Purchase Agreement	'	'
Derivative	'	'
Megawatts in a power purchase agreement that expires on March 31, 2032	440	'

Risk_Management_Activities_and9

Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Offsetting of Derivative Assets and Liabilities (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Offsetting Assets [Line Items]	'	'
Gross Amounts of Recognized Assets, subject to master netting or similar arrangements	$115	$162
Gross Amounts Offset in the Balance Sheet	-115	-131	[1]
Net Amounts of Assets Presented in the Balance Sheet	1	34	[2]
Total derivatives not subject to master netting or similar arrangement	1	3	[2]
Total Gross Amounts of Recognized Assets	116	165
Offsetting Liabilities [Line Items]	'	'
Gross Amounts of Recognized Liabilities, Subject to Master Netting or Similar Arrangements	-1,517	-1,481
Gross Amounts Offset in the Balance Sheet	120	198	[1]
Net Amounts of Liabilities Presented in the Balance Sheet	-1,494	-1,427	[2]
Total derivatives not subject to master netting or similar arrangement	-97	-144	[2]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	1,614	1,625
Letter of Credit	'	'
Offsetting Liabilities [Line Items]	'	'
Amount of letters of credit outstanding	1,000	800
Currency Swap	'	'
Offsetting Assets [Line Items]	'	'
Gross Amounts of Recognized Assets, subject to master netting or similar arrangements	64	61
Gross Amounts Offset in the Balance Sheet	-64	-33	[1]
Net Amounts of Assets Presented in the Balance Sheet	0	28	[2]
Offsetting Liabilities [Line Items]	'	'
Gross Amounts of Recognized Liabilities, Subject to Master Netting or Similar Arrangements	-15	-15	[3]
Gross Amounts Offset in the Balance Sheet	0	0	[1],[3]
Net Amounts of Liabilities Presented in the Balance Sheet	-15	-15	[2],[3]
Interest Rate Contract	'	'
Offsetting Liabilities [Line Items]	'	'
Gross Amounts of Recognized Liabilities, Subject to Master Netting or Similar Arrangements	-1,348	-1,199	[3]
Gross Amounts Offset in the Balance Sheet	0	0	[1],[3]
Net Amounts of Liabilities Presented in the Balance Sheet	-1,348	-1,199	[2],[3]
Commodity derivatives under FTP	'	'
Offsetting Assets [Line Items]	'	'
Gross Amounts of Recognized Assets, subject to master netting or similar arrangements	51	101
Gross Amounts Offset in the Balance Sheet	-51	-98	[1]
Net Amounts of Assets Presented in the Balance Sheet	0	3	[2]
Offsetting Liabilities [Line Items]	'	'
Gross Amounts of Recognized Liabilities, Subject to Master Netting or Similar Arrangements	-154	-267
Gross Amounts Offset in the Balance Sheet	120	198	[1]
Net Amounts of Liabilities Presented in the Balance Sheet	-34	-69	[2]
Total derivatives subject to master netting or similar arrangement [Member]	'	'
Offsetting Assets [Line Items]	'	'
Net Amounts of Assets Presented in the Balance Sheet	0	31	[2]
Offsetting Liabilities [Line Items]	'	'
Net Amounts of Liabilities Presented in the Balance Sheet	($1,397)	($1,283)	[2]
[1]	Amounts primarily include counterparty netting of derivative contracts, margin account deposits for futures commission merchants transactions, and cash collateral received or paid in accordance with the accounting guidance for derivatives and hedging transactions.
[2]	There are no derivative contracts subject to a master netting arrangement or similar agreement which are not offset in the balance sheets.
[3]	Letters of credit of approximately $1.0 billion and $800 million were posted as collateral at SeptemberB 30, 2014 and SeptemberB 30, 2013, respectively, to partially secure the liability positions of one of the currency swaps and one of the interest rate swaps in accordance with the collateral requirements for these derivatives.

Fair_Value_Measurements_Fair_V1

Fair Value Measurements Fair Value Measurements - Investments (Details) (USD $)	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Investment Gains (Losses)	'	'
Investment fund securities classified as trading and measured at fair value	$2,000,000,000	'
Period of time where the investor contributes capital to an investment in a private partnership - minimum	'3 years	'
Period of time where the investor contributes capital to an investment in a private partnership - maximum	'4 years	'
Minimum investment period	'10 years	'
NDT unfunded commitments related to private partnerships	113,000,000	'
Number of redemption or limited redemption options	0	'
Number of readily available quoted exchange prices for the investments	0	'
SERP	'	'
Investment Gains (Losses)	'	'
Unrealized gains (losses) on investments	1,000,000	2,000,000
LTDCP	'	'
Investment Gains (Losses)	'	'
Unrealized gains (losses) on investments	0	0
NDT	'	'
Investment Gains (Losses)	'	'
Unrealized gains (losses) on investments	35,000,000	48,000,000
ART	'	'
Investment Gains (Losses)	'	'
Unrealized gains (losses) on investments	15,000,000	33,000,000
Maximum	'	'
Investment Gains (Losses)	'	'
Equity investments not required to be measured at fair value	$1,000,000	'

Fair_Value_Measurements_Fair_V2

Fair Value Measurements Fair Value Measurements - Nonperformance Risk (Details) (USD $)	Sep. 30, 2014
In Millions, unless otherwise specified
Nonperformance Risk	'
Derivative credit valuation adjustment, assets	$1
Derivative credit valuation adjustment, liabilities	$1

Fair_Value_Measurements_Fair_V3

Fair Value Measurements Fair Value Measurements - Fair Value Measurements (Details) (USD $)	Sep. 30, 2014		Sep. 30, 2013
In Millions, unless otherwise specified
Investments	'		'
Equity securities	$162		$151
Debt securities	'		'
U.S. government corporations and agencies	85		105
Corporate debt securities	290		255
Residential mortgage-backed securities	14		25
Commercial mortgage-backed securities	7		7
Collateralized debt obligations	29		10
Private partnerships	214		159
Commingled funds	'		'
Equity security commingled funds	943	[1]	741	[1]
Debt security commingled funds	237	[1]	248	[1]
Total investments	1,981		1,701
Currency swaps	0		28
Commodity contract derivatives	1		3
Commodity derivatives under FTP	'		'
Swap contracts	0		3
Total commodity derivatives under FTP	0		3
Total	1,982		1,735
Liabilities [Abstract]	'		'
Currency swaps	15		15
Interest rate swaps	1,348		1,199
Commodity contract derivatives	97		144
Commodity derivatives under FTP	'		'
Swap contracts	34		69
Total commodity derivatives under FTP	34		69
Total	1,494		1,427
Fair Value, Inputs, Level 1	'		'
Investments	'		'
Equity securities	162		151
Debt securities	'		'
U.S. government corporations and agencies	46		38
Corporate debt securities	0		0
Residential mortgage-backed securities	0		0
Commercial mortgage-backed securities	0		0
Collateralized debt obligations	0		0
Private partnerships	0		0
Commingled funds	'		'
Equity security commingled funds	40	[1]	0	[1]
Debt security commingled funds	61	[1]	0	[1]
Total investments	309		189
Currency swaps	0		0
Commodity contract derivatives	0		0
Commodity derivatives under FTP	'		'
Swap contracts	0		0
Total commodity derivatives under FTP	0		0
Total	309		189
Liabilities [Abstract]	'		'
Currency swaps	0		0
Interest rate swaps	0		0
Commodity contract derivatives	0		0
Commodity derivatives under FTP	'		'
Swap contracts	0		0
Total commodity derivatives under FTP	0		0
Total	0		0
Fair Value, Inputs, Level 2	'		'
Investments	'		'
Equity securities	0		0
Debt securities	'		'
U.S. government corporations and agencies	39		67
Corporate debt securities	290		255
Residential mortgage-backed securities	14		25
Commercial mortgage-backed securities	7		7
Collateralized debt obligations	29		10
Private partnerships	0		0
Commingled funds	'		'
Equity security commingled funds	903	[1]	741	[1]
Debt security commingled funds	176	[1]	248	[1]
Total investments	1,458		1,353
Currency swaps	0	[2]	28	[2]
Commodity contract derivatives	0		0
Commodity derivatives under FTP	'		'
Swap contracts	0		3
Total commodity derivatives under FTP	0		3
Total	1,458		1,384
Liabilities [Abstract]	'		'
Currency swaps	15		15
Interest rate swaps	1,348		1,199
Commodity contract derivatives	0		1
Commodity derivatives under FTP	'		'
Swap contracts	34		69
Total commodity derivatives under FTP	34		69
Total	1,397		1,284
Fair Value, Inputs, Level 3	'		'
Investments	'		'
Equity securities	0		0
Debt securities	'		'
U.S. government corporations and agencies	0		0
Corporate debt securities	0		0
Residential mortgage-backed securities	0		0
Commercial mortgage-backed securities	0		0
Collateralized debt obligations	0		0
Private partnerships	214		159
Commingled funds	'		'
Equity security commingled funds	0	[1]	0	[1]
Debt security commingled funds	0	[1]	0	[1]
Total investments	214		159
Currency swaps	0		0
Commodity contract derivatives	1		3
Commodity derivatives under FTP	'		'
Swap contracts	0		0
Total commodity derivatives under FTP	0		0
Total	215		162
Liabilities [Abstract]	'		'
Currency swaps	0		0
Interest rate swaps	0		0
Commodity contract derivatives	97		143
Commodity derivatives under FTP	'		'
Swap contracts	0		0
Total commodity derivatives under FTP	0		0
Total	$97		$143
[1]	Commingled funds represent investment funds comprising multiple individual financial instruments and are classified in the table based on their existing investment portfolio as of the measurement date. Commingled funds primarily composed of one class of security are classified in that category.
[2]	Due to the right of setoff and method of settlement, TVA elects to record commodity derivatives under the FTP based on its net commodity position with the counterparty or FCM. Deposits are made to TVA's margin cash accounts held with each FCM to offset any net liability positions in full for derivatives that are transacted with FCMs. TVA records currency swaps net of cash collateral received from or paid to the counterparty. See Note 15 b Offsetting of Derivative Assets and Liabilities.

Fair_Value_Measurements_Fair_V4

Fair Value Measurements Fair Value Measurements - Fair Value Measurements Using Significant Unobservable Inputs (Details) (USD $)	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]	'	'
Commodity contract derivatives	$1,000,000	$3,000,000
Commodity contract derivatives	97,000,000	144,000,000
Liabilities	'	'
Number of contracts	2	1
Fair Value Measurements	'	'
Amount of gain (loss) recognized in income	57,000,000	'
Private Partnerships	'	'
Fair Value Measurements	'	'
Balances at beginning of period	159,000,000	53,000,000
Purchases	39,000,000	101,000,000
Issuances	0	0
Sales	-9,000,000	-4,000,000
Settlements	0	0
Net unrealized gains (losses) deferred as regulatory assets and liabilities	25,000,000	9,000,000
Balances at end of period	214,000,000	159,000,000
Commodity Contract Derivatives	'	'
Fair Value Measurements	'	'
Balances at beginning of period	-140,000,000	-267,000,000
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	33,000,000	0
Net unrealized gains (losses) deferred as regulatory assets and liabilities	11,000,000	127,000,000
Balances at end of period	-96,000,000	-140,000,000
Minimum	'	'
Assets	'	'
Fair value inputs, counterparty credit risk	2.00%	'
Fair value measurements tons per year	1,000,000,000	900,000,000
Price per ton	11.24	10.25
Liabilities	'	'
Fair value measurements tons per year	1,000,000,000	900,000,000
Price per ton	11.24	10.25
Maximum	'	'
Assets	'	'
Fair value inputs, counterparty credit risk	5.00%	21.00%
Fair value measurements tons per year	1,100,000,000	1,000,000,000
Price per ton	67.07	85.25
Liabilities	'	'
Fair value measurements tons per year	1,100,000,000	1,000,000,000
Price per ton	67.07	85.25
Fair Value, Inputs, Level 3	'	'
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]	'	'
Commodity contract derivatives	1,000,000	3,000,000
Commodity contract derivatives	$97,000,000	$143,000,000

Fair_Value_Measurements_Fair_V5

Fair Value Measurements Fair Value Measurements - Estimated Values of Financial Instruments Not Recorded at Fair Value (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013	Aug. 09, 2013
In Millions, unless otherwise specified
Estimated Values of Financial Intruments Not Recorded at Fair Value	'	'	'
EnergyRight receivables (including current portion)	$166	$150	'
Loans and other long-term receivables, net (including current portion)	81	67	'
EnergyRight purchase obligation (including current portion)	215	222	'
Unfunded Loan Commitments	18	13	'
Membership interests of VIE subject to mandatory redemption (including current portion)	50	50	40
Long-term outstanding power bonds (including current maturities), net	26,889	24,603	'
Long-term debt of variable interest entities (including current maturities)	1,425	1,386	'
Portion at Other than Fair Value Measurement [Member]	'	'	'
Estimated Values of Financial Intruments Not Recorded at Fair Value	'	'	'
EnergyRight receivables (including current portion)	156	150	'
Loans and other long-term receivables, net (including current portion)	92	73	'
EnergyRight purchase obligation (including current portion)	190	186	'
Unfunded Loan Commitments	0	0	'
Membership interests of VIE subject to mandatory redemption (including current portion)	39	40	'
Long-term outstanding power bonds (including current maturities), net	22,980	22,347	'
Long-term debt of variable interest entities (including current maturities)	$1,300	$1,300	'

Proprietary_Capital_Proprietar1

Proprietary Capital Proprietary Capital (Details) (USD $)	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Appropriation Investment	'	'	'	'	'	'	'	'	'	'	'
Amount of appropriation investment that must be repaid	$1,000,000,000	'	'	'	'	'	'	'	$1,000,000,000	'	'
Remaining appropriation investment	258,000,000	'	'	'	'	'	'	'	258,000,000	'	'
Balance at beginning of year	'	'	'	5,647,000,000	'	'	'	5,326,000,000	5,647,000,000	5,326,000,000	5,229,000,000
Net income (loss)	322,000,000	-81,000,000	295,000,000	-67,000,000	474,000,000	-12,000,000	54,000,000	-245,000,000	469,000,000	271,000,000	60,000,000
Return of power program appropriation investment	'	'	'	'	'	'	'	'	10,000,000	20,000,000	20,000,000
Return on power program appropriation investment	'	'	'	'	'	'	'	'	4,000,000	7,000,000	7,000,000
Balance at end of year	6,104,000,000	'	'	'	5,647,000,000	'	'	'	6,104,000,000	5,647,000,000	5,326,000,000
Net proprietary capital at September 30	6,104,000,000	'	'	'	5,647,000,000	'	'	'	6,104,000,000	5,647,000,000	'
Computed average interest rate payable	1.97%	'	'	'	2.10%	'	'	'	1.97%	2.10%	2.33%
Nonpower Programs Appropriation Investment	'	'	'	'	'	'	'	'	'	'	'
Appropriation Investment	'	'	'	'	'	'	'	'	'	'	'
Balance at beginning of year	'	'	'	4,351,000,000	'	'	'	4,351,000,000	4,351,000,000	4,351,000,000	'
Return of power program appropriation investment	'	'	'	'	'	'	'	'	0	0	'
Balance at end of year	4,351,000,000	'	'	'	4,351,000,000	'	'	'	4,351,000,000	4,351,000,000	'
Power Program Appropriation Investment	'	'	'	'	'	'	'	'	'	'	'
Appropriation Investment	'	'	'	'	'	'	'	'	'	'	'
Balance at beginning of year	'	'	'	268,000,000	'	'	'	288,000,000	268,000,000	288,000,000	308,000,000
Net income (loss)	'	'	'	'	'	'	'	'	0	0	0
Return of power program appropriation investment	'	'	'	'	'	'	'	'	10,000,000	20,000,000	20,000,000
Return on power program appropriation investment	'	'	'	'	'	'	'	'	0	0	0
Balance at end of year	258,000,000	'	'	'	268,000,000	'	'	'	258,000,000	268,000,000	288,000,000
Power Program Retained Earnings	'	'	'	'	'	'	'	'	'	'	'
Appropriation Investment	'	'	'	'	'	'	'	'	'	'	'
Balance at beginning of year	'	'	'	4,767,000,000	'	'	'	4,492,000,000	4,767,000,000	4,492,000,000	4,429,000,000
Net income (loss)	'	'	'	'	'	'	'	'	477,000,000	282,000,000	70,000,000
Return of power program appropriation investment	'	'	'	'	'	'	'	'	0	0	0
Return on power program appropriation investment	'	'	'	'	'	'	'	'	4,000,000	7,000,000	7,000,000
Balance at end of year	5,240,000,000	'	'	'	4,767,000,000	'	'	'	5,240,000,000	4,767,000,000	4,492,000,000
Net proprietary capital at September 30	5,498,000,000	'	'	'	5,035,000,000	'	'	'	5,498,000,000	5,035,000,000	'
Nonpower Programs Retained Earnings	'	'	'	'	'	'	'	'	'	'	'
Appropriation Investment	'	'	'	'	'	'	'	'	'	'	'
Balance at beginning of year	'	'	'	-3,742,000,000	'	'	'	-3,731,000,000	-3,742,000,000	-3,731,000,000	'
Net income (loss)	'	'	'	'	'	'	'	'	-8,000,000	-11,000,000	'
Return on power program appropriation investment	'	'	'	'	'	'	'	'	0	0	'
Balance at end of year	-3,750,000,000	'	'	'	-3,742,000,000	'	'	'	-3,750,000,000	-3,742,000,000	'
Net proprietary capital at September 30	601,000,000	'	'	'	609,000,000	'	'	'	601,000,000	609,000,000	'
Power Program Appropriation Investment	'	'	'	'	'	'	'	'	'	'	'
Appropriation Investment	'	'	'	'	'	'	'	'	'	'	'
Return of power program appropriation investment	'	'	'	'	'	'	'	'	$10,000,000	$20,000,000	'

Proprietary_Capital_Proprietar2

Proprietary Capital Proprietary Capital - Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss)	'	'	'
Net effect on earnings	$0	$0	$0
Net unrealized gain (loss) on future cash flow hedges	4	78	99
Reclassification to earnings from cash flow hedges	2	1	35
Reclassification to earnings from cash flow hedges in the next twelve months	$37	'	'

Other_Income_Expense_Net_Other1

Other Income (Expense), Net Other Income (Expense), Net (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Other Income (Expense), Net	'	'	'
Interest income	$23	$23	$21
External services	19	18	7
Gains (losses) on investments	6	4	5
Miscellaneous	1	-1	0
Total other income (expense), net	$49	$44	$33

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information Supplemental Cash Flow Information (Details) (USD $)	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Supplemental Cash Flow Information	'	'	'
Interest paid	$1,300,000,000	$1,300,000,000	$1,400,000,000
Interest capitalized	175,000,000	168,000,000	171,000,000
Bellefonte amounts included in Construction expenditures	'	162,000,000	212,000,000
Financing non-cash activity for capital leases	70,000,000	20,000,000	6,000,000
Accounts payable and accrued liabilities	'	'	'
Supplemental Cash Flow Information	'	'	'
Construction in progress and Nuclear fuel expenditures	$391,000,000	$270,000,000	$204,000,000

Benefit_Plans_Components_of_Be

Benefit Plans Components of Benefit Plans (Details) (USD $)

12 Months Ended

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Dec. 31, 2011

Dec. 31, 2010

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Dec. 31, 2014

Number_of_defined_benefit_plan_structures

Number_of_defined_benefit_plan_investment_funds

Original benefit structure

Cash Balance Benefit Structure

Defined Contribution Only

Maximum

Maximum

Maximum

Scenario, Forecast [Member]

Years

Original benefit structure

Cash Balance Benefit Structure

Defined Contribution Only

plans

Defined Benefit Plan Disclosure

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of defined benefit plans

1

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of defined contribution plans

1

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of unfunded post-retirement health care plans

2

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of benefit plan structures

2

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of consecutive highest base pay years

3

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of straight-time earnings for cash balance benefit credit

6.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage added to consumer price index for interest credit of cash balance benefit

3.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Minimum interest credit percentage for cash balance benefit

6.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum interest credit percentage for cash balance benefit

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Rate of cash balance benefit credit for calendar year

'

6.00%

'

'

'

'

'

'

'

'

'

'

'

6.00%

Number of defined benefit plan investment funds

'

2

'

'

'

'

'

'

'

'

'

'

'

'

Fixed and variable fund annual maximum contribution

$10,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Fixed fund balance interest credits after January 1, 2010

6.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Fixed fund balance credit percentage subtracted from the actuarial rate of return after January 1, 2010

0.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

Fixed fund interest credit rate

6.00%

'

6.00%

'

'

'

'

'

'

'

'

'

'

'

Fixed fund interest credit amount

33,000,000

'

36,000,000

'

'

'

'

'

'

'

'

'

'

'

Defined contribution plan employer matching contribution rate

'

'

'

'

'

'

'

0.25

0.75

0.75

'

'

'

'

Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay

'

'

'

'

'

'

'

'

'

'

1.50%

4.50%

4.50%

'

Defined Contribution Plan, Automatic Employer Contribution

'

'

'

'

'

'

'

'

'

4.50%

'

'

'

'

Defined contribution plan contribution amount

$35,000,000

'

$34,000,000

'

$34,000,000

'

'

'

'

'

'

'

'

'

Market-related value phase-in period number of years

3

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of years during which cost of living adjustment changed

'

'

'

'

'

'

'4 years

'

'

'

'

'

'

'

Cost of Living Adjustment Cap

'

2.30%

'

0.00%

'

1.15%

0.00%

'

'

'

'

'

'

1.53%

Cost of living adjustment cap for calendar year 2014 and forward

'

'

'

'

'

'

'

'

'

'

'

'

'

5.00%

Retirement age of eligibility for cost of living adjustment after January 1, 2010

'

'

'

'

'

'

60

'

'

'

'

'

'

'

Benefit_Plans_Obligations_and_

Benefit Plans Obligations and Funded Status (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2012
Pension Benefits	'		'		'
Change in benefit obligation	'		'		'
Benefit obligation	$12,265		$11,471		$11,995
Service cost	130		154		139
Interest cost	558		468		490
Plan participants' contributions	28		29		'
Amendments	2		4		'
Actuarial loss (gain)	-722		549		'
Net transfers from variable fund/401(k) plan	13		4		'
Expenses paid	-6		-6		'
Benefits paid	-653		-628		'
Change in plan assets	'		'		'
Fair value of net plan assets	7,507		7,221		7,029
Actual return on plan assets	648		787		'
Employer contributions	256	[1]	6	[1]	'
Defined Benefit Plan, Funded Status of Plan [Abstract]	'		'		'
Funded status	-4,758		-4,250		'
Discount rate	4.45%		5.00%		4.00%
Amount of defined benefit plan actuarial gain (loss) from discount rate change	-729		1,400		'
Amount of defined benefit plan actuarial gain (loss) from reduction in workforce	-36		'		'
Impact of previously excluded retiree benefits	'		-705		'
Amount of defined benefit plan actuarial gain (loss) from retirement rate assumption change	88		'		'
Other Post-retirement Benefits	'		'		'
Change in benefit obligation	'		'		'
Benefit obligation	652		656		811
Service cost	18		24		19
Interest cost	32		31		35
Collections	93	[2]	79	[2]	'
Amendments	0		0		'
Actuarial loss (gain)	21		163		'
Net transfers from variable fund/401(k) plan	0		0		'
Expenses paid	0		0		'
Benefits paid	-126		-126		'
Change in plan assets	'		'		'
Fair value of net plan assets	0		0		0
Actual return on plan assets	0		0		'
Employer contributions	33	[1]	47	[1]	'
Defined Benefit Plan, Funded Status of Plan [Abstract]	'		'		'
Funded status	-652		-656		'
Discount rate	4.50%		5.05%		4.00%
Amount of defined benefit plan actuarial gain (loss) from discount rate change	-43		93		'
Amount of defined benefit plan actuarial gain (loss) from reduction in workforce	-17		'		'
Amount of defined benefit plan actuarial gain (loss) from excise tax change	'		-33		'
Amount of defined benefit plan actuarial gain (loss) from plan demographic experience changes	64		43		'
Amount of defined benefit plan actuarial gain (loss) from retirement rate assumption change	$16		'		'
[1]	Other Post-Retirement Benefits Employer contributions are reduced by federal reinsurance payments and provider discounts and rebates.
[2]	Collections include retiree contributions as well as federal reinsurance payments and provider discounts and rebates.

Benefit_Plans_Amounts_Recogniz

Benefit Plans Amounts Recognized on TVA's Consolidated Balance Sheets (Details) (USD $)	Sep. 30, 2014		Sep. 30, 2013
In Millions, unless otherwise specified
Defined Benefit Plan Disclosure	'		'
Regulatory assets	$8,994		$9,131
Accounts payable and accrued liabilities	-2,029		-1,627
Post-retirement and post-employment benefit obligations	-5,839		-5,348
Pension Benefits	'		'
Defined Benefit Plan Disclosure	'		'
Regulatory assets	4,157		3,910
Accounts payable and accrued liabilities	-5		-5
Post-retirement and post-employment benefit obligations	-4,753	[1]	-4,245	[1]
Other Post-retirement Benefits	'		'
Defined Benefit Plan Disclosure	'		'
Regulatory assets	140		166
Accounts payable and accrued liabilities	-38		-39
Post-retirement and post-employment benefit obligations	-614	[1]	-617	[1]
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent [Member]	'		'
Defined Benefit Plan Disclosure	'		'
Postemployment benefits liability, noncurrent	$472		$486
[1]	Table above excludes $472 million and $486 million of post-employment benefit costs that are recorded in Post-retirement and post-employment benefit obligations on the Consolidated Balance Sheets at SeptemberB 30, 2014 and 2013, respectively.

Benefit_Plans_Postretirement_B

Benefit Plans Postretirement Benefit Costs Deferred as Regulatory Assets (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Defined Benefit Plan Disclosure	'	'
Regulatory assets	$8,994	$9,131
Pension Benefits	'	'
Defined Benefit Plan Disclosure	'	'
Unrecognized prior service cost (credit)	-180	-203
Unrecognized net loss	4,337	4,113
Regulatory assets	4,157	3,910
Other Post-retirement Benefits	'	'
Defined Benefit Plan Disclosure	'	'
Unrecognized prior service cost (credit)	-39	-45
Unrecognized net loss	179	211
Regulatory assets	$140	$166

Benefit_Plans_Projected_Benefi

Benefit Plans Projected Benefit Obligations and Accumulated Benefit Obligations in Exess of Plan Assets (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Defined Benefit Plan Disclosure	'	'
Projected benefit obligation	$12,265	$11,471
Accumulated benefit obligation	12,039	11,216
Fair value of net plan assets	$7,507	$7,221

Benefit_Plans_Components_of_Ne

Benefit Plans Components of Net Periodic Benefit Cost (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Pension Benefits	'	'	'
Defined Benefit Plan Disclosure	'	'	'
Service cost	$130	$154	$139
Interest cost	558	468	490
Expected return on plan assets	-435	-428	-437
Amortization of prior service credit	-21	-22	-23
Recognized net actuarial loss	285	377	361
Total net periodic benefit cost	517	549	530
Other Post-retirement Benefits	'	'	'
Defined Benefit Plan Disclosure	'	'	'
Service cost	18	24	19
Interest cost	32	31	35
Expected return on plan assets	0	0	0
Amortization of prior service credit	-6	-6	-6
Recognized net actuarial loss	11	25	29
Total net periodic benefit cost	$55	$74	$77

Benefit_Plans_Expected_Amortiz

Benefit Plans Expected Amortization of Regulatory Assets in Next Fiscal Year (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Defined Benefit Plan Disclosure	'
Prior service cost (credit)	($27)
Net actuarial loss	285
Pension Benefits	'
Defined Benefit Plan Disclosure	'
Prior service cost (credit)	-21
Net actuarial loss	277
Other Post-retirement Benefits	'
Defined Benefit Plan Disclosure	'
Prior service cost (credit)	-6
Net actuarial loss	$8

Benefit_Plans_Actuarial_Assump

Benefit Plans Actuarial Assumptions (Details)

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2010

Sep. 30, 2009

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2011

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2015

Sep. 30, 2020

Pension Benefits

Pension Benefits

Pension Benefits

Other Post-retirement Benefits

Other Post-retirement Benefits

Other Post-retirement Benefits

Other Post-retirement Benefits

Minimum

Maximum

Scenario, Forecast [Member]

Scenario, Forecast [Member]

Defined Benefit Plan Disclosure

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Discount rate

'

'

'

'

'

4.45%

5.00%

4.00%

4.50%

5.05%

4.00%

'

'

'

'

'

Rate of compensation increase

5.70%

5.72%

'

'

'

5.70%

5.72%

'

'

'

'

'

3.50%

13.00%

'

'

Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year

'

'

'

'

'

'

'

'

7.50%

8.00%

8.50%

8.00%

'

'

'

'

Defined Benefit Plan, Ultimate Health Care Cost Trend Rate

'

'

'

'

'

'

'

'

5.00%

5.00%

5.00%

'

'

'

'

'

Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate

'

'

'

'

'

'

'

'

'2019

'2019

'

'

'

'

'

'

Discount rate

'

'

'

'

'

5.00%

4.00%

'

5.05%

4.00%

'

'

'

'

'

'

Expected return on plan assets

7.25%

7.25%

7.25%

'

'

7.25%

7.25%

'

'

'

'

'

'

'

7.00%

'

Period during which actual company compensation experience study performed

'5 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Rate of compensation increase

5.72%

4.44%

4.43%

'

'

5.72%

4.44%

'

'

'

'

'

'

'

'

'

Minimum percentage increase in twelve-month average CPI-U necessary to receive COLA

1.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of years during which cost of living adjustment changed

'

'

'

'4 years

'

'

'

'

'

'

'

'

'

'

'

'

Retirement age of eligibility for cost of living adjustment after January 1, 2010

'

'

'

60

'

'

'

'

'

'

'

'

'

'

'

'

Retirement age of eligibility for cost of living adjustment before January 1, 2010

'

'

'

55

'

'

'

'

'

'

'

'

'

'

'

'

Cost of living adjustment assumption

2.00%

1.60%

'

'

2.50%

'

'

'

'

'

'

'

1.00%

5.00%

'

2.50%

Rate of inflation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2.00%

'

Benefit_Plans_Sensitivity_to_C

Benefit Plans Sensitivity to Certain Changes in Pension Assumptions (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Discount rate	'
Defined Benefit Plan Disclosure	'
Change in Assumption	-0.25%
Impact on Pension Cost	$18
Impact on Projected Benefit Obligation	369
Rate of return on plan assets	'
Defined Benefit Plan Disclosure	'
Change in Assumption	-0.25%
Impact on Pension Cost	$15

Benefit_Plans_Sensitivity_to_C1

Benefit Plans Sensitivity to Changes in Assumed Health Care Cost Trend Rates (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Defined Benefit Plan Disclosure	'
Effect of one percentage point increase on total service and interest cost components	$7
Effect of one percentage point decrease on total service and interest cost components	-7
Effect of one percentage point increase on end-of-year accumulated postretirement benefit obligation	89
Effect of one percentage point decrease on end-of-year accumulated postretirement benefit obligation	($93)

Benefit_Plans_Asset_Holdings_D

Benefit Plans Asset Holdings (Details)	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Equity securities	'	'
Defined Benefit Plan Disclosure	'	'
New Policy Target Allocation	47.00%	'
Target Allocation	32.00%	'
Plan Asset Allocations	43.00%	48.00%
Private equity funds	'	'
Defined Benefit Plan Disclosure	'	'
Target Allocation	10.00%	'
Plan Asset Allocations	5.00%	6.00%
Low volatility global public equity [Member]	'	'
Defined Benefit Plan Disclosure	'	'
Target Allocation	5.00%	'
Plan Asset Allocations	1.00%	0.00%
Cash and cash equivalents	'	'
Defined Benefit Plan Disclosure	'	'
Target Allocation	2.00%	'
Plan Asset Allocations	2.00%	2.00%
Core fixed income	'	'
Defined Benefit Plan Disclosure	'	'
Target Allocation	5.00%	'
Plan Asset Allocations	5.00%	5.00%
Long-term core fixed income	'	'
Defined Benefit Plan Disclosure	'	'
Target Allocation	5.00%	'
Plan Asset Allocations	5.00%	4.00%
Investment grade credit	'	'
Defined Benefit Plan Disclosure	'	'
Target Allocation	6.00%	'
Plan Asset Allocations	6.00%	6.00%
Foreign Corporate Debt Securities [Member]	'	'
Defined Benefit Plan Disclosure	'	'
Target Allocation	5.00%	'
Plan Asset Allocations	5.00%	0.00%
High yield fixed income	'	'
Defined Benefit Plan Disclosure	'	'
Target Allocation	5.00%	'
Plan Asset Allocations	6.00%	10.00%
Global TIPS	'	'
Defined Benefit Plan Disclosure	'	'
Target Allocation	5.00%	'
Plan Asset Allocations	5.00%	7.00%
Private real assets	'	'
Defined Benefit Plan Disclosure	'	'
New Policy Target Allocation	10.00%	'
Target Allocation	10.00%	'
Plan Asset Allocations	7.00%	7.00%
Commodities	'	'
Defined Benefit Plan Disclosure	'	'
Target Allocation	5.00%	'
Plan Asset Allocations	4.00%	0.00%
MLPs	'	'
Defined Benefit Plan Disclosure	'	'
Target Allocation	5.00%	'
Plan Asset Allocations	6.00%	5.00%
Fixed income	'	'
Defined Benefit Plan Disclosure	'	'
New Policy Target Allocation	28.00%	'
Public real assets	'	'
Defined Benefit Plan Disclosure	'	'
New Policy Target Allocation	15.00%	'

Benefit_Plans_Fair_Value_Measu

Benefit Plans Fair Value Measurements (Details) (USD $)

12 Months Ended

12 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2014

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Preferred securities [Member]

Preferred securities [Member]

Preferred securities [Member]

Preferred securities [Member]

Preferred securities [Member]

Preferred securities [Member]

Preferred securities [Member]

Preferred securities [Member]

Corporate debt securities

Corporate debt securities

Corporate debt securities

Corporate debt securities

Corporate debt securities

Corporate debt securities

Corporate debt securities

Corporate debt securities

Residential mortgage-backed securities

Residential mortgage-backed securities

Residential mortgage-backed securities

Residential mortgage-backed securities

Residential mortgage-backed securities

Residential mortgage-backed securities

Residential mortgage-backed securities

Residential mortgage-backed securities

Debt securities issued by U.S. Treasury and other U.S. government agencies

Debt securities issued by U.S. Treasury and other U.S. government agencies

Debt securities issued by U.S. Treasury and other U.S. government agencies

Debt securities issued by U.S. Treasury and other U.S. government agencies

Debt securities issued by U.S. Treasury and other U.S. government agencies

Debt securities issued by U.S. Treasury and other U.S. government agencies

Debt securities issued by U.S. Treasury and other U.S. government agencies

Debt securities issued by U.S. Treasury and other U.S. government agencies

Debt securities issued by foreign governments

Debt securities issued by foreign governments

Debt securities issued by foreign governments

Debt securities issued by foreign governments

Debt securities issued by foreign governments

Debt securities issued by foreign governments

Debt securities issued by foreign governments

Debt securities issued by foreign governments

Asset-backed securities

Asset-backed securities

Asset-backed securities

Asset-backed securities

Asset-backed securities

Asset-backed securities

Asset-backed securities

Asset-backed securities

Debt securities issued by state/local governments

Debt securities issued by state/local governments

Debt securities issued by state/local governments

Debt securities issued by state/local governments

Debt securities issued by state/local governments

Debt securities issued by state/local governments

Debt securities issued by state/local governments

Debt securities issued by state/local governments

Commercial mortgage-backed securities

Commercial mortgage-backed securities

Commercial mortgage-backed securities

Commercial mortgage-backed securities

Commercial mortgage-backed securities

Commercial mortgage-backed securities

Commercial mortgage-backed securities

Commercial mortgage-backed securities

Equity security commingled funds

Equity security commingled funds

Equity security commingled funds

Equity security commingled funds

Equity security commingled funds

Equity security commingled funds

Equity security commingled funds

Equity security commingled funds

Debt security commingled funds

Debt security commingled funds

Debt security commingled funds

Debt security commingled funds

Debt security commingled funds

Debt security commingled funds

Debt security commingled funds

Debt security commingled funds

Commodity commingled funds

Commodity commingled funds

Commodity commingled funds

Commodity commingled funds

Blended security commingled funds

Blended security commingled funds

Blended security commingled funds

Blended security commingled funds

Blended security commingled funds

Blended security commingled funds

Blended security commingled funds

Blended security commingled funds

Institutional mutual funds

Institutional mutual funds

Institutional mutual funds

Institutional mutual funds

Institutional mutual funds

Institutional mutual funds

Institutional mutual funds

Institutional mutual funds

Cash and cash equivalents

Cash and cash equivalents

Cash and cash equivalents

Cash and cash equivalents

Cash and cash equivalents

Cash and cash equivalents

Cash and cash equivalents

Cash and cash equivalents

Certificates of deposit

Certificates of deposit

Certificates of deposit

Certificates of deposit

Private equity funds

Private equity funds

Private equity funds

Private equity funds

Private equity funds

Private equity funds

Private equity funds

Private equity funds

Private real estate funds

Private real estate funds

Private real estate funds

Private real estate funds

Private real estate funds

Private real estate funds

Private real estate funds

Private real estate funds

Treasury bills, U.S. Government notes and securities held as futures and other derivative collateral

Treasury bills, U.S. Government notes and securities held as futures and other derivative collateral

Treasury bills, U.S. Government notes and securities held as futures and other derivative collateral

Treasury bills, U.S. Government notes and securities held as futures and other derivative collateral

Treasury bills, U.S. Government notes and securities held as futures and other derivative collateral

Treasury bills, U.S. Government notes and securities held as futures and other derivative collateral

Treasury bills, U.S. Government notes and securities held as futures and other derivative collateral

Treasury bills, U.S. Government notes and securities held as futures and other derivative collateral

Securities lending commingled funds

Securities lending commingled funds

Securities lending commingled funds

Securities lending commingled funds

Securities lending commingled funds

Securities lending commingled funds

Securities lending commingled funds

Securities lending commingled funds

Purchased options

Purchased options

Purchased options

Purchased options

Purchased options

Purchased options

Purchased options

Foreign currency forward

Foreign currency forward

Foreign currency forward

Foreign currency forward

Foreign currency forward

Foreign currency forward

Foreign currency forward

Foreign currency forward

Futures

Futures

Futures

Futures

Written option obligations

Written option obligations

Written option obligations

Written option obligations

Written option obligations

Written option obligations

Written option obligations

Written option obligations

Credit default swaps

Credit default swaps

Credit default swaps

Credit default swaps

Minimum

Maximum

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Number_of_extensions

Years

Years

Number_of_extensions

Defined Benefit Plan Disclosure

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair value of gross plan assets

$7,600

[1],[2]

$7,363

$1,804

$1,855

$5,148

$4,852

$648

$656

$633

$1,669

$1,689

$1,668

$1,686

$0

$0

$1

$3

$37

$22

$5

$17

$32

$0

$0

$5

$1,326

$1,352

$0

$0

$1,304

$1,334

$22

$18

$204

$355

$0

$0

$201

$352

$3

$3

$93

$113

$93

$113

$0

$0

$0

$0

$225

$31

$0

$0

$218

$30

$7

$1

$176

$120

$0

$0

$147

$110

$29

$10

$30

$36

$0

$0

$29

$36

$1

$0

$23

$21

$0

$0

$20

$18

$3

$3

$1,106

$1,182

$0

$0

$1,106

$1,182

$0

$0

$661

$786

$0

$0

$661

$786

$0

$0

$332

$0

$332

$0

$228

$263

$0

$0

$228

$263

$0

$0

$28

$26

$28

$26

$0

$0

$0

$0

$464

$395

$0

$1

$464

$394

$0

$0

$19

$0

$19

$0

$481

$528

$0

$0

$0

$0

$481

$528

$435

$382

$0

$0

$334

$297

$101

$85

$35

$39

$10

$8

$25

$31

$0

$0

$2

$3

$0

$0

$2

$3

$0

$0

$18

$6

$0

$0

$18

$6

$0

$8

$6

$0

$0

$8

$6

$0

$0

'

'

'

'

'

$4

'

$4

'

$0

'

$0

$4

$0

$4

'

'

'

Derivative liabilities

26

[1],[3]

8

11

0

15

8

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

8

6

0

0

8

6

0

0

11

11

0

0

7

1

0

0

7

1

0

0

1

0

1

0

'

'

Net payables

65

131

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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Payables for collateral on loaned securities

$2

$3

'

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Number of years partnerships in private equity generally continue

'

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10

12

Number of one year extensions for partnerships in private equity

'

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3

4

Voting percentage required to desolve partnership in private equity

80.00%

'

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'

[1]

Excludes approximately $65 million in net payables associated with security purchases and sales and various other payables.

[2]

Excludes a $3 million payable for collateral on loaned securities in connection with TVARSbs participation in securities lending programs.

[3]

Excludes a $2 million payable for collateral on loaned securities in connection with TVARSbs participation in securities lending programs.

Benefit_Plans_Fair_Value_Measu1

Benefit Plans Fair Value Measurements Using Significant Unobservable Inputs (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2012
Defined Benefit Plan Disclosure	'		'	'
Fair value of gross plan assets	$7,600	[1],[2]	$7,363	'
Fair Value, Inputs, Level 3	'		'	'
Defined Benefit Plan Disclosure	'		'	'
Fair value of gross plan assets	648		656	633
Net realized/unrealized gains and losses	50		45	'
Purchases, sales, issuances, and settlements	-53		-21	'
Transfers in and/or out of Level 3	($5)		($1)	'
[1]	Excludes approximately $65 million in net payables associated with security purchases and sales and various other payables.
[2]	Excludes a $3 million payable for collateral on loaned securities in connection with TVARSbs participation in securities lending programs.

Benefit_Plans_Estimated_Future

Benefit Plans Estimated Future Benefit Payments (Details) (USD $)	Sep. 30, 2014
In Millions, unless otherwise specified
Pension Benefits	'
Defined Benefit Plan Disclosure	'
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	$712
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	715
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	720
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	724
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	731
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	3,759
Other Post-retirement Benefits	'
Defined Benefit Plan Disclosure	'
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	39
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	40
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	41
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	41
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	41
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	$186

Benefit_Plans_Contributions_De

Benefit Plans Contributions (Details) (USD $)

12 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2011

Sep. 30, 2009

Sep. 30, 2014

Sep. 30, 2015

Sep. 30, 2015

Sep. 30, 2015

Sep. 30, 2015

Supplemental Employee Retirement Plans, Defined Benefit

Other Post-retirement Benefits

Other Post-retirement Benefits

Pension Benefits

Pension Benefits

Other Pension Plans, Defined Benefit

Other Pension Plans, Defined Benefit

Other Pension Plans, Defined Benefit

Minimum

Scenario, Forecast [Member]

Scenario, Forecast [Member]

Scenario, Forecast [Member]

Scenario, Forecast [Member]

Other Pension Plans, Defined Benefit

Supplemental Employee Retirement Plans, Defined Benefit

Other Pension Plans, Defined Benefit

Minimum

Other Pension Plans, Defined Benefit

Defined Benefit Plan Disclosure

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Employer contributions

'

$6

$33

[1]

$47

[1]

$256

[1]

$6

[1]

$250

$270

$1,000

$198

'

$5

$275

$215

Other postretirement benefit contributions

$47

'

'

'

'

'

'

'

'

'

$39

'

'

'

[1]

Other Post-Retirement Benefits Employer contributions are reduced by federal reinsurance payments and provider discounts and rebates.

Benefit_Plans_Other_Postemploy

Benefit Plans Other Postemployment Benefits (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Other Post-Employment Benefits	'	'	'
Discount rate	2.52%	2.64%	1.65%
Period expense	$34	($8)	$52
Postemployment benefits liability	520	535	597
Amount of Postemployment benefit actuarial gain (loss) from discount rate change	'	45	'
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent [Member]	'	'	'
Other Post-Employment Benefits	'	'	'
Postemployment benefits liability, noncurrent	472	486	'
Accounts payable and accrued liabilities	'	'	'
Other Post-Employment Benefits	'	'	'
Postemployment benefits liability, current	$48	$49	'

Commitments_and_Contingencies_1

Commitments and Contingencies Commitments and Contingencies - Table (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013
Obligations	'		'
Time period shown for contractual commitments	'5 years		'
2015	$1,064		'
2016	65		'
2017	1,590		'
2018	1,718		'
2019	1,070		'
Thereafter	18,829		'
Total	24,336		'
Total	18		13
2015	100		'
2016	100		'
2017	100		'
2018	100		'
2019	10		'
Thereafter	0		'
Total	410		'
Foreign currency exchange loss	44		43
Net discount on sale of Bonds	89		'
Debt	'		'
Obligations	'		'
2015	1,628		'
2016	32		'
2017	1,555		'
2018	1,682		'
2019	1,032		'
Thereafter	17,692		'
Total	23,621	[1]	'
Debt of VIEs	'		'
Obligations	'		'
2015	32		'
2016	33		'
2017	35		'
2018	36		'
2019	38		'
Thereafter	1,137		'
Total	1,311		'
Financial Instruments Subject to Mandatory Redemption, Financial Instrument [Domain]	'		'
Obligations	'		'
2015	2		'
2016	2		'
2017	2		'
2018	2		'
2019	2		'
Thereafter	29		'
Total	39		'
Lease Obligations - Capital	'		'
Obligations	'		'
2015	13		'
2016	13		'
2017	13		'
2018	13		'
2019	12		'
Thereafter	167		'
Total	231		'
Lease Obligations - Non-Cancelable Operating	'		'
Obligations	'		'
2015	38		'
2016	36		'
2017	34		'
2018	27		'
2019	25		'
Thereafter	63		'
Total	223		'
Purchase Obligations - Power	'		'
Obligations	'		'
2015	220		'
2016	222		'
2017	232		'
2018	235		'
2019	239		'
Thereafter	3,364		'
Total	4,512		'
Purchase Obligations - Fuel	'		'
Obligations	'		'
2015	1,335		'
2016	862		'
2017	477		'
2018	552		'
2019	492		'
Thereafter	1,579		'
Total	5,297		'
Purchase Obligations - Other	'		'
Obligations	'		'
2015	304		'
2016	215		'
2017	202		'
2018	199		'
2019	192		'
Thereafter	1,640		'
Total	2,752		'
Unfunded Loan Commitment [Member]	'		'
Obligations	'		'
2015	13		'
Total	13		'
Payments on Other Financings	'		'
Obligations	'		'
2015	104		'
2016	104		'
2017	104		'
2018	104		'
2019	96		'
Thereafter	305		'
Total	817		'
Total	'		'
Obligations	'		'
2015	3,689		'
2016	1,519		'
2017	2,654		'
2018	2,850		'
2019	2,128		'
Thereafter	25,976		'
Total	$38,816		'
[1]	Does not include noncash items of foreign currency exchange loss of $44 million and net discount on sale of Bonds of $89 million.

Commitments_and_Contingencies_2

Commitments and Contingencies Commitments and Contingencies - Energy Prepayment Obligations (Details) (USD $)	Sep. 30, 2014
In Millions, unless otherwise specified
Obligations	'
2015	$100
2016	100
2017	100
2018	100
2019	10
Thereafter	0
Total	$410

Commitments_and_Contingencies_3

Commitments and Contingencies Commitments and Contingencies - Debt (Details) (USD $)	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Aug. 09, 2013
	variable_interest_entities
Debt Instrument	'	'	'
Remaining terms of the agreements, high end of range	'18 years	'	'
Outstanding discount notes	$596,000,000	'	'
Outstanding long-term debt including current maturities)	23,000,000,000	'	'
Long-term and short-term debt combined	23,600,000,000	'	'
Number of VIEs	3	'	'
Outstanding long-term debt (including current maturities) of VIEs	1,300,000,000	'	'
Membership interests of VIE subject to mandatory redemption	$50,000,000	$50,000,000	$40,000,000

Commitments_and_Contingencies_4

Commitments and Contingencies Commitments and Contingencies - Leases (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Leases	'	'	'
Lease terms low end of range	'1	'	'
Lease terms high end of range	'80	'	'
Cost of financing	$124	'	'
Rental expense for operating leases	$75	$71	$67

Commitments_and_Contingencies_5

Commitments and Contingencies Commitments and Contingencies - Purchase Obligations (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Aug. 09, 2013
	Facilities
	Hours
	Megawatts
Obligations	'	'	'	'
Membership interests of VIE subject to mandatory redemption	$50	$50	'	$40
Megawatts provided under power purchase obligations	1,621	'	'	'
Remaining terms of the agreements, high end of range	'18 years	'	'	'
Power purchased under agreement	293	322	447	'
Number of U.S. Army Corps of Engineers hydroelectric facilities contracted with to obtain power	8	'	'	'
Agreement termination notice period	'3 years	'	'	'
Minimum required hours of power	1,500	'	'	'
Megawatt allocation	405	'	'	'
Maximum term length for the purchase and transportation of coal	'6 years	'	'	'
Maximum term for purchase of enriched uranium and fabrication of nuclear fuel assemblies	'16 years	'	'	'
Purchase Agreements Required by Federal Law	'	'	'	'
Obligations	'	'	'	'
Megawatts provided under power purchase obligations	890	'	'	'
Number of suppliers	6	'	'	'
Purchase Obligations - Coal	'	'	'	'
Obligations	'	'	'	'
Long-term purchase commitment	1,600	'	'	'
Purchase Obligations - Nuclear Fuel	'	'	'	'
Obligations	'	'	'	'
Long-term purchase commitment	3,700	'	'	'
Purchase Obligations - Other	'	'	'	'
Obligations	'	'	'	'
Long-term purchase commitment	$2,752	'	'	'

Commitments_and_Contingencies_6

Commitments and Contingencies Commitments and Contingencies - Contingencies (Details) (USD $)	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
	reactors
	Procedures
	Insurance_layers
	Units
	Sites
Contingencies	'	'	'
Nuclear liability insurance	$375,000,000	'	'
Assessment from licensees for each licensed reactor	127,000,000	'	'
Number of licensed reactors in US	104	'	'
Nuclear accident assessment limitation per year per unit	19,000,000	'	'
Number of licensed nuclear units	6	'	'
Maximum assessment per nuclear incident	764,000,000	'	'
Maximum payment required per accident in any one year	114,000,000	'	'
Total amount of protection available	13,000,000,000	'	'
Surcharge for legal expenses	5.00%	'	'
The U.S. Congress is required to take action if these layes are exhausted	2	'	'
Amount of property, decommissioning, and decontamination insurance carried	5,100,000,000	'	'
Amount of insurance available for loss at any one site	2,100,000,000	'	'
Number of sites	1	'	'
Maximum amount of retrospective premiums	120,000,000	'	'
Maximum idemnity if a covered accident tasks or keeps a nuclear unit offline	490,000,000	'	'
Maximum amount of retrospective premiums	35,000,000	'	'
Number of procedures for determining estimates for the costs of nuclear decommissioning	2	'	'
Amount spent to reduce emissions since 1970	5,900,000,000	'	'
Amount spent to reduce emissions	378,000,000	197,000,000	55,000,000
Possible additional future costs for compliance with Clean Air Act requirements	900,000,000	'	'
Amount of settlement for potential liability related to soil cleanup	300,000	'	'
Amount of settlement for potential liability related to EPA study of site	8,000	'	'
Remaining natural resource damages are less than	1,000,000	'	'
Estimated liability for cleanup and similar environmental work on a non-discounted basis	15,000,000	15,000,000	'
Expected increase (decrease) in operation and maintenance expense	-500,000,000	'	'
Restructuring and Related Cost, Number of Positions Eliminated	2,000	'	'
Severance cost liability	45,000,000	0	'
Nuclear	'	'	'
Contingencies	'	'	'
Future estimated decommissioning cost	2,100,000,000	'	'
Non-nuclear	'	'	'
Contingencies	'	'	'
Future estimated decommissioning cost	$1,100,000,000	'	'

Commitments_and_Contingencies_7

Commitments and Contingencies Commitments and Contingencies - Legal Proceedings (Details) (USD $)

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

3 Months Ended

1 Months Ended

Dec. 31, 2010

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Apr. 30, 2011

Jun. 30, 2011

Sep. 30, 2014

Jun. 30, 2014

Jun. 30, 2010

Sep. 30, 2010

Mar. 31, 2010

Dec. 31, 2010

Jun. 30, 2012

Jul. 31, 2013

31-May-13

Aug. 31, 2011

Jun. 30, 2008

Sep. 30, 2012

Nov. 30, 2009

Dec. 31, 2011

Aug. 31, 2011

Sep. 30, 2014

Sep. 30, 2014

General

Environmental Agreements

Environmental Agreements

Kingston Ash Spill

Kingston Ash Spill

Kingston Ash Spill

Case Involving Tennessee Valley Authority Retirement System

Case Involving Tennessee Valley Authority Retirement System

Case Involving Tennessee Valley Authority Retirement System

Case Involving the NRC Waste Confidence Decision on Spent Nuclear Fuel Storage

Administrative Proceedings Regarding Sequoyah U1 and U2 [Member]

Administrative Proceedings Regarding Sequoyah U1 and U2 [Member]

Administrative Proceedings Regarding Bellefonte Units 3 and 4

Administrative Proceedings Regarding Bellefonte Units 3 and 4

Administrative Proceedings Regarding Bellefonte Units 3 and 4

Administrative Proceedings Regarding Watts Bar Nuclear Plant Unit 2

Petitions Resulting from Japanese Nuclear Events

Petitions Resulting from Japanese Nuclear Events

Other long-term liabilities

Accounts payable and accrued liabilities

Groups

Units

Legal_actions

Legal_actions

People

Legal_actions

Legal_actions

People

Legal_actions

Legal_actions

General

General

Agreements

Megawatts

Legal_actions

Legal Proceedings

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Accrual for Environmental Loss Contingencies, Gross

'

$15,000,000

$15,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Legal loss contingency accrual

'

'

'

172,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

108,000,000

64,000,000

Estimated range of losses low end of range

'

'

'

172,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Estimated range of losses high end of range

'

'

'

173,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of similar environmental agreements entered into

'

'

'

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of environmental agreements entered into with the EPA

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of environmental agreements entered into with Alabama, Kentucky, North Carolina, and Tennessee

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of environmental agreements entered into with environmental advocacy groups

'

'

'

'

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of units to be idled

'

'

'

'

'

18

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Megawatts option 1

'

'

'

'

'

2,200

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Megawatts option 2

'

'

'

'

'

3,500

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amount to be invested in certain environmental projects

'

'

'

'

'

290,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amount to be provided to fund environmental projects

'

'

'

'

'

60,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amount to pay civil penalties

'

'

'

'

'

10,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of lawsuits filed

'

'

'

'

'

'

78

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of lawsuits dismissed

'

'

'

'

'

'

'

15

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency, Claims Dismissed, Number

'

'

'

'

'

'

63

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of active lawsuits

'

'

'

'

'

'

9

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Payments for Legal Settlements

'

'

'

'

'

'

28,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Civil penalty order issued June 1, 2010

'

'

'

'

'

'

'

'

12,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amount of civil penalty order satisfied

'

'

'

'

'

'

10,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit against civil penalty order

'

'

'

'

'

'

2,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Down payment on natural resource damages

'

'

'

'

'

'

$750,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of participants that filed suit

'

'

'

'

'

'

'

'

'

'

8

'

'

'

'

'

'

'

'

'

'

'

'

Number of TVARS Board members

'

'

'

'

'

'

'

'

'

'

6

'

'

'

'

'

'

'

'

'

'

'

'

Number of Board Members Appointed

'

'

'

'

'

'

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

Number of defendants that filed a motion to dismiss

'

'

'

'

'

'

'

'

'

'

5

'

'

'

'

'

'

'

'

'

'

'

'

Retirement age of eligibility for cost of living adjustment before January 1, 2010

55

'

'

'

'

'

'

'

'

'

'

55

'

'

'

'

'

'

'

'

'

'

'

Retirement age of eligibility for cost of living adjustment after January 1, 2010

60

'

'

'

'

'

'

'

'

'

'

60

'

'

'

'

'

'

'

'

'

'

'

Number of days to file an ammended complaint

'

'

'

'

'

'

'

'

'

'14 days

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of years that spent fuel can be stored after a plant's license is terminated

'

'

'

'

'

'

'

'

'

'

'

'

'60 years

'

'

'

'

'

'

'

'

'

'

Number of contentions submitted by BREDL BEST and MATRR

'

'

'

'

'

'

'

'

'

'

'

'

'

'

8

'

'

'

'

'

'

'

'

Opposed contentions

'

'

'

'

'

'

'

'

'

'

'

'

'

'

8

'

'

'

'

'

'

'

'

Number of petitioners with standing

'

'

'

'

'

'

'

'

'

'

'

'

'

1

'

'

'

'

'

'

'

'

'

Number of petitioners

'

'

'

'

'

'

'

'

'

'

'

'

'

3

'

'

'

'

'

'

'

'

'

Number of contentions dismissed

'

'

'

'

'

'

'

'

'

'

'

'

'

7

'

'

'

'

1

'

'

'

'

Number of contentions left

'

'

'

'

'

'

'

'

'

'

'

'

'

1

'

'

2

'

'

'

'

'

'

Number of admitted contentions submitted by BREDL and SACE

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4

'

'

'

'

'

'

Number of contentions submitted by BREDL and SACE

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

20

'

'

'

'

'

'

Number of contentions no longer admitted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2

'

'

'

'

'

'

Number of BREDL contentions

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1

'

'

'

'

'

Number of contentions admitted for hearing

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2

'

'

'

'

Number of SACE contentions

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1

'

'

7

'

'

'

'

Number of other petitioners

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4

'

'

'

'

Number of contentions remaining

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1

'

'

'

'

Number of units at John Sevier Fossil

'

4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Units Affected by Paradise Case

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of requests accepted by the NRC

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5

'

'

'

Number of separate petitions filed by the Natural Resources Defense Council

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

12

'

'

Number of individual defendants

'

'

'

'

'

'

'

'

'

'

6

'

'

'

'

'

'

'

'

'

'

'

'

Remaining defendant

'

'

'

'

'

'

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

Related_Parties_Related_Partie1

Related Parties Related Parties (Details) (USD $)	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Related Parties	'	'	'
Amount of appropriations currently received	$0	'	'
Amount of appropriation investment that must be repaid	1,000,000,000	'	'
Current borrowing capacity	150,000,000	'	'
Sales of electricity	128,000,000	120,000,000	117,000,000
Other income	137,000,000	102,000,000	164,000,000
Operating and maintenance	286,000,000	314,000,000	375,000,000
Cash and cash equivalents	35,000,000	38,000,000	32,000,000
Accounts receivable, net	85,000,000	58,000,000	49,000,000
Accounts payable and accrued liabilities	146,000,000	133,000,000	204,000,000
Long-term power bonds, net	3,000,000	0	0
Return on power program appropriation investment	4,000,000	7,000,000	7,000,000
Return of power program appropriation investment	$10,000,000	$20,000,000	$20,000,000

Unaudited_Quarterly_Financial_2

Unaudited Quarterly Financial Information Unaudited Quarterly Financial Information (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Quarterly Financial Information Disclosure [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Operating revenues	$3,166	$2,651	$2,938	$2,382	$3,034	$2,602	$2,741	$2,579	$11,137	$10,956	$11,220
Operating expenses	2,569	2,453	2,362	2,164	2,276	2,324	2,380	2,523	9,548	9,503	9,920
Operating income	597	198	576	218	758	278	361	56	1,589	1,453	1,300
Net income (loss)	$322	($81)	$295	($67)	$474	($12)	$54	($245)	$469	$271	$60