| Comprehensive Income (Loss) Note [Text Block] |
| 11. | Other Comprehensive Income (Loss) |
A summary of other comprehensive income and loss is provided below:
| | | | | | | Tax | | | | |
| | | Before-Tax | | | (Expense) | | | Net-of-Tax | |
| | | Amount | | | or Benefit | | | Amount | |
| Three Months Ended June 30, 2026 | | | | | | | | | | | | |
| Interest rate swaps: | | | | | | | | | | | | |
| Unrealized gains | | $ | 506,950 | | | $ | (130,489 | ) | | $ | 376,461 | |
| Transfer of realized gains to interest expense | | | (231,048 | ) | | | 59,473 | | | | (171,575 | ) |
| Net interest rate swaps | | | 275,902 | | | | (71,016 | ) | | | 204,886 | |
| Defined benefit plans: | | | | | | | | | | | | |
| Amortization of net actuarial gains | | | (7,829 | ) | | | 2,015 | | | | (5,814 | ) |
| Other comprehensive income | | $ | 268,073 | | | $ | (69,001 | ) | | $ | 199,072 | |
| Three Months Ended June 30, 2025 | | | | | | | | | | | | |
| Interest rate swaps: | | | | | | | | | | | | |
| Unrealized losses | | $ | (20,816 | ) | | $ | 5,358 | | | $ | (15,458 | ) |
| Transfer of realized gains to interest expense | | | (323,513 | ) | | | 83,273 | | | | (240,240 | ) |
| Net interest rate swaps | | | (344,329 | ) | | | 88,631 | | | | (255,698 | ) |
| Defined benefit plans: | | | | | | | | | | | | |
| Amortization of net actuarial gains | | | (10,379 | ) | | | 2,671 | | | | (7,708 | ) |
| Other comprehensive loss | | $ | (354,708 | ) | | $ | 91,302 | | | $ | (263,406 | ) |
| | | | | | | Tax | | | | | |
| | | Before-Tax | | | (Expense) | | | Net-of-Tax | |
| | | Amount | | | or Benefit | | | Amount | |
| Nine Months Ended June 30, 2026 | | | | | | | | | | | | |
| Interest rate swaps: | | | | | | | | | | | | |
| Unrealized gains | | $ | 1,132,692 | | | $ | (291,556 | ) | | $ | 841,136 | |
| Transfer of realized gains to interest expense | | | (829,579 | ) | | | 213,535 | | | | (616,044 | ) |
| Net interest rate swaps | | | 303,113 | | | | (78,021 | ) | | | 225,092 | |
| Defined benefit plans: | | | | | | | | | | | | |
| Amortization of net actuarial gains | | | (23,487 | ) | | | 6,045 | | | | (17,442 | ) |
| Other comprehensive income | | $ | 279,626 | | | $ | (71,976 | ) | | $ | 207,650 | |
| Nine Months Ended June 30, 2025 | | | | | | | | | | | | |
| Interest rate swaps: | | | | | | | | | | | | |
| Unrealized gains | | $ | 507,492 | | | $ | (130,628 | ) | | $ | 376,864 | |
| Transfer of realized gains to interest expense | | | (1,034,976 | ) | | | 266,403 | | | | (768,573 | ) |
| Net interest rate swaps | | | (527,484 | ) | | | 135,775 | | | | (391,709 | ) |
| Defined benefit plans: | | | | | | | | | | | | |
| Amortization of net actuarial gains | | | (31,134 | ) | | | 8,013 | | | | (23,121 | ) |
| Other comprehensive loss | | $ | (558,618 | ) | | $ | 143,788 | | | $ | (414,830 | ) |
The amortization of actuarial gains and losses, reflected in the preceding table, relate to the unregulated operations of the Company. Actuarial gains and losses attributable to the regulated operations are included as a regulatory asset. See Note 13 for a schedule of regulatory assets. The amortization of actual gains and losses is recognized as a component of net periodic pension and postretirement benefit costs under other income, net in the condensed consolidated statements of income.
Reconciliation of Accumulated Other Comprehensive Income
| | | | | | | | | | | Accumulated | |
| | | | | | | | | | | Other | |
| | | Interest Rate | | | Defined Benefit | | | Comprehensive | |
| | | Swaps | | | Plans | | | Income | |
| Balance at September 30, 2025 | | $ | 664,568 | | | $ | (402,836 | ) | | $ | 261,732 | |
| Other comprehensive income (loss) | | | 225,092 | | | | (17,442 | ) | | | 207,650 | |
| Balance at June 30, 2026 | | $ | 889,660 | | | $ | (420,278 | ) | | $ | 469,382 | |
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