Real Estate - Text (Detail) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2026 |
Mar. 31, 2025 |
Sep. 30, 2025 |
|
| Real Estate Properties [Line Items] | |||||
| Real estate | $ 2,709.7 | $ 2,709.7 | $ 2,645.1 | ||
| Payments to Acquire Residential Real Estate | 156.2 | ||||
| Payments to Develop Real Estate Assets | 537.8 | ||||
| Asset, Impairment Loss | 0.0 | $ 0.0 | |||
| Loss on Contract Termination | 6.3 | $ 0.9 | 7.1 | $ 2.0 | |
| Developed and under development projects | |||||
| Real Estate Properties [Line Items] | |||||
| Real estate | 2,552.7 | 2,552.7 | 2,465.1 | ||
| Land held for future development | |||||
| Real Estate Properties [Line Items] | |||||
| Real estate | $ 157.0 | $ 157.0 | $ 180.0 | ||
| D.R. Horton, Inc. [Member] | Minimum | |||||
| Real Estate Properties [Line Items] | |||||
| Related Party Transaction, Rate | 12.00% | ||||
| D.R. Horton, Inc. [Member] | Maximum | |||||
| Real Estate Properties [Line Items] | |||||
| Related Party Transaction, Rate | 16.00% | ||||