Supplemental Guarantor Information - Consolidating Balance Sheets (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
ASSETS
Cash and cash equivalents	$ 1,473.1	$ 1,007.8	$ 1,303.2	$ 1,383.8
Restricted cash	32.9	16.5
Investments in subsidiaries	0.0	0.0
Inventories	10,395.0	9,237.1
Investment in unconsolidated entities	11.0	0.0
Mortgage loans held for sale	796.4	587.3
Deferred income taxes, net	194.0	365.0
Property and equipment, net	401.1	325.0
Other assets	701.9	565.9
Goodwill	109.2	80.0
Intercompany receivables	0.0	0.0
Total assets	14,114.6	12,184.6
LIABILITIES & EQUITY
Accounts payable and other liabilities	1,752.2	1,565.4
Intercompany payables	0.0	0.0
Notes payable	3,203.5	2,871.6
Total liabilities	4,955.7	4,437.0
Total stockholders' equity	8,984.4	7,747.1
Noncontrolling interests	174.5	0.5
Total equity	9,158.9	7,747.6	6,793.0	5,895.4
Total liabilities and equity	14,114.6	12,184.6
Consolidation, Eliminations [Member]
ASSETS
Cash and cash equivalents	0.0	0.0	0.0	0.0
Restricted cash	0.0	0.0
Investments in subsidiaries	(6,344.9)	(4,812.6)
Inventories	(11.2)	0.0
Investment in unconsolidated entities	0.0
Mortgage loans held for sale	0.0	0.0
Deferred income taxes, net	2.5	0.0
Property and equipment, net	(6.9)	(5.8)
Other assets	(45.2)	0.0
Goodwill	0.0	0.0
Intercompany receivables	(273.5)	(1,047.7)
Total assets	(6,679.2)	(5,866.1)
LIABILITIES & EQUITY
Accounts payable and other liabilities	(49.1)	(2.0)
Intercompany payables	(273.5)	(1,047.7)
Notes payable	0.0	0.0
Total liabilities	(322.6)	(1,049.7)
Total stockholders' equity	(6,355.6)	(4,816.4)
Noncontrolling interests	(1.0)	0.0
Total equity	(6,356.6)	(4,816.4)
Total liabilities and equity	(6,679.2)	(5,866.1)
D.R Horton, Inc. [Member]
ASSETS
Cash and cash equivalents	908.1	780.9	1,076.4	1,217.7
Restricted cash	6.6	7.8
Investments in subsidiaries	6,344.9	4,812.6
Inventories	4,037.1	3,540.4
Investment in unconsolidated entities	0.0
Mortgage loans held for sale	0.0	0.0
Deferred income taxes, net	69.2	138.5
Property and equipment, net	111.2	104.8
Other assets	306.6	245.5
Goodwill	0.0	0.0
Intercompany receivables	246.2	1,047.7
Total assets	12,029.9	10,678.2
LIABILITIES & EQUITY
Accounts payable and other liabilities	590.8	483.9
Intercompany payables	0.0	0.0
Notes payable	2,443.9	2,443.4
Total liabilities	3,034.7	2,927.3
Total stockholders' equity	8,995.2	7,750.9
Noncontrolling interests	0.0	0.0
Total equity	8,995.2	7,750.9
Total liabilities and equity	12,029.9	10,678.2
Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	158.7	154.5	154.0	94.6
Restricted cash	2.0	1.5
Investments in subsidiaries	0.0	0.0
Inventories	5,824.1	5,579.9
Investment in unconsolidated entities	0.0
Mortgage loans held for sale	0.0	0.0
Deferred income taxes, net	105.0	223.6
Property and equipment, net	66.1	59.7
Other assets	361.3	259.7
Goodwill	80.0	80.0
Intercompany receivables	27.3	0.0
Total assets	6,624.5	6,358.9
LIABILITIES & EQUITY
Accounts payable and other liabilities	1,000.4	956.9
Intercompany payables	0.0	732.2
Notes payable	2.1	8.2
Total liabilities	1,002.5	1,697.3
Total stockholders' equity	5,622.0	4,661.6
Noncontrolling interests	0.0	0.0
Total equity	5,622.0	4,661.6
Total liabilities and equity	6,624.5	6,358.9
Non-Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	406.3	72.4	$ 72.8	$ 71.5
Restricted cash	24.3	7.2
Investments in subsidiaries	0.0	0.0
Inventories	545.0	116.8
Investment in unconsolidated entities	11.0
Mortgage loans held for sale	796.4	587.3
Deferred income taxes, net	17.3	2.9
Property and equipment, net	230.7	166.3
Other assets	79.2	60.7
Goodwill	29.2	0.0
Intercompany receivables	0.0	0.0
Total assets	2,139.4	1,013.6
LIABILITIES & EQUITY
Accounts payable and other liabilities	210.1	126.6
Intercompany payables	273.5	315.5
Notes payable	757.5	420.0
Total liabilities	1,241.1	862.1
Total stockholders' equity	722.8	151.0
Noncontrolling interests	175.5	0.5
Total equity	898.3	151.5
Total liabilities and equity	$ 2,139.4	$ 1,013.6