Notes Payable (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Mar. 31, 2023	Jun. 30, 2023	Sep. 30, 2022	Sep. 30, 2020	Sep. 30, 2019
Estimate of Fair Value Measurement [Member]
Debt Instrument [Line Items]
Notes payable, Fair value			$ 5,900.0	$ 5,700.0
Letters of Credit Outstanding, Amount			253.2
Notes payable			6,105.3	6,066.9
Fair Value, Inputs, Level 2 [Member]
Debt Instrument [Line Items]
Notes payable, Fair value			3,000.0	3,100.0
Fair Value, Inputs, Level 3 [Member]
Debt Instrument [Line Items]
Notes payable, Fair value			2,900.0	2,600.0
Intersegment Eliminations [Member]
Debt Instrument [Line Items]
Notes payable			0.0	0.0
Forestar Group [Member]
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense			5.3	6.5
Notes payable			707.2	706.0
Financial Services [Member]
Debt Instrument [Line Items]
Notes payable			1,685.6	1,618.3
Forestar Group [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity			410.0
Line of Credit Facility, Maximum Borrowing Capacity			$ 600.0
Letters of credit, sublimit borrowing capacity, as a percentage			50.00%
Revolving credit facility			$ 0.0	0.0
Letters of Credit Outstanding, Amount			29.8
Line of Credit Facility, Remaining Borrowing Capacity			380.2
Authorized Repurchase Of Debt Securities					$ 30.0
Debt Repurchase Authorization Remaining			30.0
Letter of Credit, Maximum Borrowing Capacity (in dollars)			100.0
Notes payable			707.2	706.0
Home Building Consolidated
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense			9.2	12.2
Line of Credit Facility, Current Borrowing Capacity			2,190.0
Line of Credit Facility, Maximum Borrowing Capacity			$ 3,000.0
Letters of credit, sublimit borrowing capacity, as a percentage			100.00%
Revolving credit facility			$ 0.0	0.0
Letters of Credit Outstanding, Amount			223.4
Line of Credit Facility, Remaining Borrowing Capacity			1,970.0
Authorized Repurchase Of Debt Securities						$ 500.0
Debt Repurchase Authorization Remaining			500.0
Notes payable			2,712.5	2,942.6
Rental
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity			1,025.0
Line of Credit Facility, Maximum Borrowing Capacity			$ 1,250.0
Letters of credit, sublimit borrowing capacity, as a percentage			50.00%
Revolving credit facility			$ 1,000.0	800.0
Line of Credit Facility, Remaining Borrowing Capacity			25.0
Letter of Credit, Maximum Borrowing Capacity (in dollars)			100.0
Notes payable			$ 1,000.0	800.0
Line of Credit Facility, Interest Rate at Period End			7.50%
Proceeds from Lines of Credit			$ 575.0
Repayments of Lines of Credit			$ 375.0
4.75% senior notes due 2023 [Member] | Home Building Consolidated
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			4.75%
Maturities of Senior Debt		$ 300.0
Notes payable			$ 0.0	299.9
5.75% senior notes due 2023 [Member] | Home Building Consolidated
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			5.75%
Notes payable			$ 400.0	399.6
5.75% senior notes due 2023 [Member] | Home Building Consolidated | Subsequent Event [Member]
Debt Instrument [Line Items]
Maturities of Senior Debt	$ 400.0
Debt Instrument, Redemption Price, Percentage	100.00%
SeniorNoteFortyTwo [Member] | Home Building Consolidated
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.50%
Notes payable			$ 498.8	498.2
SeniorNoteFortyFour | Home Building Consolidated
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.60%
Notes payable			$ 497.8	497.1
Senior Note Forty Six | Home Building Consolidated
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			1.30%
Notes payable			$ 596.3	595.5
Senior Note Forty Five | Home Building Consolidated
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			1.40%
Notes payable			$ 496.3	495.7
Senior Note Member Forty Six | Forestar Group [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.85%
Notes payable			$ 397.2	396.5
Senior Note Member Forty Three | Forestar Group [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			5.00%
Notes payable			$ 297.5	297.0
Secured Debt [Member] | Forestar Group [Member]
Debt Instrument [Line Items]
Notes payable			12.5	12.5
Secured Debt [Member] | Home Building Consolidated
Debt Instrument [Line Items]
Notes payable			223.3	156.6
Commitments to Extend Credit | Financial Services [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity			2,000.0
Line of Credit Facility, Maximum Borrowing Capacity			2,300.0
Deposit Liabilities, Collateral Issued, Financial Instruments			2,030.0
Participating Mortgage Loans, Mortgage Obligations, Amount			$ 1,990.0
Assets Sold under Agreements to Repurchase, Interest Rate			6.70%
Notes payable			$ 1,385.9	1,618.3
Warehouse Agreement Borrowings | Financial Services [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity			300.0
Deposit Liabilities, Collateral Issued, Financial Instruments			376.5
Participating Mortgage Loans, Mortgage Obligations, Amount			$ 360.0
Assets Sold under Agreements to Repurchase, Interest Rate			6.50%
Notes payable			$ 299.7	$ 0.0