v3.26.1
Real Estate - Text (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Sep. 30, 2025
Real Estate Properties [Line Items]          
Real estate $ 2,711.5   $ 2,711.5   $ 2,645.1
Payments to Acquire Residential Real Estate     214.8    
Payments to Develop Real Estate Assets     791.2    
Asset, Impairment Loss     0.0 $ 0.0  
Loss on Contract Termination 0.8 $ 1.9 8.0 $ 3.9  
Developed and under development projects          
Real Estate Properties [Line Items]          
Real estate 2,557.5   2,557.5   2,465.1
Land held for future development          
Real Estate Properties [Line Items]          
Real estate $ 154.0   $ 154.0   $ 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%