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Summary of Significant Accounting Policies Summary of Significant Accounting Policies - General (Details) People in Millions, $ in Millions | 12 Months Ended |
--- | --- | ---
Sep. 30, 2019 USD ($) People | Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) | Sep. 30, 2014 USD ($)
Population of Service Area |  |  |  |
Cash | $ 299 | $ 299 |  |
Total possible amount of BLEU payments | 166 |  |  |
Loans and other long-term receivables, net (including current portion) | $ 120 | 123 |  |
Population of TVA's service area (number of people) | People | 10 |  |  |
Allowance for uncollectible accounts - loans |  | 1 |  |
Revenue Capitalized During Pre-Commercial Operations | $ 0 | 11 | $ (22) |
Fuel Cost Capitalized During Pre-Commercial Operations |  | 19 |  |
Recorded cost for emission allowances granted by the Environmental Protection Agency | 0 |  |  |
Payments attributable to blended low-enriched uranium fuel currently in use | 165 |  |  |
BLEU fuel obligation | 1 |  |  |
Reimbursements from DOE | 23 |  |  |
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents | 322 | 322 |  |
Accounts receivable from DOE | 6 |  |  |
Appropriation-investment power program | 258 | 258 |  | $ 1,000
Total |  |  |  |
Population of Service Area |  |  |  |
Discounts reducing electricity sales | $ 4 | 46 |  |
MLGW |  |  |  |
Population of Service Area |  |  |  |
Deferred revenue, revenue recognized |  | $ 100 |  |

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