Note 7 - Income Taxes (Details Textual) - State and Local Jurisdiction [Member] - USD ($) $ in Millions |
3 Months Ended | ||
|---|---|---|---|
Jun. 30, 2024 |
Sep. 30, 2023 |
Jun. 30, 2023 |
|
| Iowa, Kansas, and Arkansas Department of Revenue [Member] | |||
| Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability | $ (41) | ||
| Arkansas Department of Revenue [Member] | |||
| Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability | $ (8) | ||
| Nebraska Department of Revenue [Member] | |||
| Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability | $ (73) | ||