| Line Item | Jun 30, 2026 | Mar 31, 2026 | Dec 31, 2025 | Sep 30, 2025 | Jun 30, 2025 | Mar 31, 2025 | Dec 31, 2024 | Sep 30, 2024 | Jun 30, 2024 | Mar 31, 2024 | Dec 31, 2023 | Sep 30, 2023 | Jun 30, 2023 | Mar 31, 2023 | Dec 31, 2022 | Sep 30, 2022 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Operating revenue | ||||||||||||||||
| Total operating revenue | ||||||||||||||||
| YoY growth | +2.8% | +2.3% | +2.9% | +6.7% | ||||||||||||
| Operating expenses | ||||||||||||||||
| Total operating expenses | ||||||||||||||||
| % of revenue | 81.3% | 83.5% | 83.4% | 80.4% | ||||||||||||
| Operating income | ||||||||||||||||
| % of revenue | 18.7% | 16.5% | 16.6% | 19.6% | ||||||||||||
| Investment income | ||||||||||||||||
| Net investment income | ||||||||||||||||
| Net realized and unrealized investment gains (losses) | ||||||||||||||||
| Net impairment losses recognized in earnings | ||||||||||||||||
| Total investment income | ||||||||||||||||
| Other income | ||||||||||||||||
| Income before income taxes | ||||||||||||||||
| Income tax expense | ||||||||||||||||
| Net income | ||||||||||||||||
| % of revenue | 16.5% | 14.9% | 6.7% | 17.1% | ||||||||||||
| Common stock - basic (in dollars per share) | — | — | — | — | ||||||||||||
| Common stock - diluted (in dollars per share) | — | — | — | — |