Notes Payable - Homebuilding Textuals (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2024
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	$ 281.5		$ 281.5
Home Building Consolidated
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	2,305.0		2,305.0	$ 2,190.0
Line of Credit Facility, Current Borrowing Capacity Excluding Accordion Feature	2,230.0		2,230.0
Line of Credit Facility, Maximum Borrowing Capacity	$ 3,000.0		$ 3,000.0
Letters of credit, sublimit borrowing capacity, as a percentage	100.00%		100.00%
Borrowings outstanding on revolving credit facility	$ 0.0		$ 0.0		$ 0.0
Letters of Credit Outstanding, Amount	244.3		244.3
Line of Credit Facility, Remaining Borrowing Capacity	2,060.0		2,060.0
Authorized Repurchase Of Debt Securities	500.0		500.0
Debt Repurchase Authorization Remaining	$ 500.0		500.0
Home Building Consolidated | 2.5% Senior Notes due 2024 [Member]
Debt Instrument [Line Items]
Maturities of Senior Debt			$ 500.0
Debt Instrument, Interest Rate, Stated Percentage	2.50%		2.50%
Home Building Consolidated | 5.5% Senior Note due 2035
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.50%		5.50%
Debt Instrument, Issued, Principal		$ 700.0
Debt Instrument, Maturity Date		Oct. 15, 2035
Debt Instrument, Interest Rate, Effective Percentage	5.60%		5.60%
Home Building Consolidated | 4.85% Senior Notes due 2030
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.85%		4.85%
Debt Instrument, Issued, Principal	$ 500.0
Debt Instrument, Maturity Date	Oct. 15, 2030
Debt Instrument, Interest Rate, Effective Percentage	5.10%		5.10%
Home Building Consolidated | Credit Facility Maturing December 18, 2029
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 2,040.0		$ 2,040.0
Line of Credit Facility, Expiration Date			Dec. 18, 2029
Home Building Consolidated | Credit Facility Maturing October 28, 2027
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 265.0		$ 265.0
Line of Credit Facility, Expiration Date			Oct. 28, 2027