Impact of New Accounting Standards and Interpretations	12 Months Ended
Sep. 30, 2015
Accounting Changes and Error Corrections [Abstract]
Impact of New Accounting Standards and Interpretations	Impact of New Accounting Standards and Interpretations The following accounting standard became effective for TVA on October 1, 2014. Liabilities. In February 2013, the Financial Accounting Standards Board ("FASB") issued guidance on liabilities, 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 became effective for TVA on October 1, 2014, and is applied on a retrospective basis for all comparative periods presented. Adoption of this guidance did not have a material impact on TVA’s financial condition, results of operations, or cash flows. The following accounting standard was adopted by TVA as of September 30, 2015. Fair Value Measurements. In May 2015, the FASB issued guidance that removes the requirement to categorize within the fair value hierarchy all investments for which fair value is measured using the net asset value per share practical expedient. Investments measured at net asset value per share using the practical expedient will be presented as a reconciling item between the fair value hierarchy disclosure and the investment line item on the statement of financial position. This guidance also removes the requirement to make certain disclosures for all investments that are eligible to be measured at fair value using the net asset value per share practical expedient. Rather, those disclosures are limited to investments for which the entity has elected to measure the fair value using the practical expedient. The guidance is effective for fiscal years beginning after December 15, 2015, and for interim periods within those years, and early adoption is permitted. The guidance is required to be applied retrospectively to all prior periods presented. TVA has early adopted this guidance as of September 30, 2015. Adoption of this guidance 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, 2015, were not effective and had not been adopted by TVA. Revenue Recognition. In May 2014, the 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. In August 2015, the FASB issued a one-year deferral of the effective date. The standard becomes effective for TVA on October 1, 2018, and allows for either a full retrospective or a modified retrospective application. Early adoption of the standard is permitted for TVA on October 1, 2017. 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. Consolidation. In February 2015, the FASB issued guidance that amends the consolidation analysis for VIEs as well as voting interest entities. The standard reduces the number of consolidation models through the elimination of the indefinite deferral for certain entities that was previously allowed and places more emphasis on risk of loss when determining a controlling financial interest. The standard becomes effective for TVA on October 1, 2016, and allows for either a full retrospective or a modified retrospective application. 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. Debt Issuance Costs. In April 2015, the FASB issued guidance that changes the presentation of debt issuance costs in financial statements. This standard requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct reduction of that debt liability, consistent with debt discounts. The guidance does not change the recognition and measurement of debt issuance costs. The standard becomes effective for TVA on October 1, 2016, and early adoption is permitted. The guidance is required to be applied retrospectively to all prior periods presented. TVA has early adopted this guidance as of October 1, 2015. If the guidance had been adopted by TVA as of September 30, 2015, TVA would have reclassified $80 million of debt issuance costs from Other long-term assets as a reduction to Long-term power bonds, net and Long-term debt, net of variable interest entities. Inventory Valuation. In July 2015, the FASB issued guidance that changes the model used for the subsequent measurement of inventory from the previous lower of cost or market model, to the lower of cost or net realizable value. The guidance applies only to inventory valued using methods other than last-in, first out (“LIFO”) or the retail inventory method (for example, first-in, first-out (“FIFO”) or average cost). This amendment is intended to simplify the subsequent measurement of inventory. The standard becomes effective for TVA on October 1, 2017, including interim periods within that fiscal year, and is required to be applied prospectively. Early adoption is permitted. TVA is currently evaluating the potential impact of these changes on its consolidated financial statements.

Impact of New Accounting Standards and Interpretations

The following accounting standard became effective for TVA on October 1, 2014.

Liabilities. In February 2013, the Financial Accounting Standards Board ("FASB") issued guidance on liabilities, 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 became effective for TVA on October 1, 2014, and is applied on a retrospective basis for all comparative periods presented. Adoption of this guidance did not have a material impact on TVA’s financial condition, results of operations, or cash flows.

The following accounting standard was adopted by TVA as of September 30, 2015.

Fair Value Measurements. In May 2015, the FASB issued guidance that removes the requirement to categorize within the fair value hierarchy all investments for which fair value is measured using the net asset value per share practical expedient. Investments measured at net asset value per share using the practical expedient will be presented as a reconciling item between the fair value hierarchy disclosure and the investment line item on the statement of financial position. This guidance also removes the requirement to make certain disclosures for all investments that are eligible to be measured at fair value using the net asset value per share practical expedient. Rather, those disclosures are limited to investments for which the entity has elected to measure the fair value using the practical expedient. The guidance is effective for fiscal years beginning after December 15, 2015, and for interim periods within those years, and early adoption is permitted. The guidance is required to be applied retrospectively to all prior periods presented. TVA has early adopted this guidance as of September 30, 2015. Adoption of this guidance 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, 2015, were not effective and had not been adopted by TVA.

Revenue Recognition. In May 2014, the 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. In August 2015, the FASB issued a one-year deferral of the effective date. The standard becomes effective for TVA on October 1, 2018, and allows for either a full retrospective or a modified retrospective application. Early adoption of the standard is permitted for TVA on October 1, 2017. 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.

Consolidation. In February 2015, the FASB issued guidance that amends the consolidation analysis for VIEs as well as voting interest entities. The standard reduces the number of consolidation models through the elimination of the indefinite deferral for certain entities that was previously allowed and places more emphasis on risk of loss when determining a controlling financial interest. The standard becomes effective for TVA on October 1, 2016, and allows for either a full retrospective or a modified retrospective application. 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.

Debt Issuance Costs. In April 2015, the FASB issued guidance that changes the presentation of debt issuance costs in financial statements. This standard requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct reduction of that debt liability, consistent with debt discounts. The guidance does not change the recognition and measurement of debt issuance costs. The standard becomes effective for TVA on October 1, 2016, and early adoption is permitted. The guidance is required to be applied retrospectively to all prior periods presented. TVA has early adopted this guidance as of October 1, 2015. If the guidance had been adopted by TVA as of September 30, 2015, TVA would have reclassified $80 million of debt issuance costs from Other long-term assets as a reduction to Long-term power bonds, net and Long-term debt, net of variable interest entities.

Inventory Valuation. In July 2015, the FASB issued guidance that changes the model used for the subsequent measurement of inventory from the previous lower of cost or market model, to the lower of cost or net realizable value. The guidance applies only to inventory valued using methods other than last-in, first out (“LIFO”) or the retail inventory method (for example, first-in, first-out (“FIFO”) or average cost). This amendment is intended to simplify the subsequent measurement of inventory. The standard becomes effective for TVA on October 1, 2017, including interim periods within that fiscal year, and is required to be applied prospectively. Early adoption is permitted. TVA is currently evaluating the potential impact of these changes on its consolidated financial statements.