Supplemental Guarantor Information - Consolidating Statements of Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Condensed Financial Statements, Captions [Line Items]
Revenues	$ 4,505.2	$ 4,435.3	$ 3,794.7	$ 3,332.7	$ 4,159.1	$ 3,776.4	$ 3,251.3	$ 2,904.2	$ 16,068.0	$ 14,091.0	$ 12,157.4
Unaudited Supplemental Consolidating Statement of Operations
Cost of sales									12,398.1	11,042.8	9,502.6
Selling, general and administrative expense									1,676.8	1,471.6	1,320.3
Goodwill impairment									0.0	0.0	7.2
Equity in earnings of unconsolidated entities									(2.8)	0.0	0.0
Gain on sale of assets									(18.8)	0.0	(4.5)
Other (income) expense									(45.3)	(25.5)	(21.7)
Income before income taxes	607.7	616.2	444.8	391.2	485.5	444.5	353.9	318.1	2,060.0	1,602.1	1,353.5
Income tax expense (benefit)	138.8	162.5	94.0	202.4	172.3	155.5	124.7	111.2	597.7	563.7	467.2
Equity in net income of subsidiaries, net of tax									0.0	0.0	0.0
Net income	468.9	453.7	350.8	188.8					1,462.3	1,038.4	886.3
Net income attributable to noncontrolling interests	2.8	(0.1)	(0.2)	(0.5)					2.0	0.0	0.0
Net income attributable to D.R. Horton, Inc.	$ 466.1	$ 453.8	$ 351.0	$ 189.3	$ 313.2	$ 289.0	$ 229.2	$ 206.9	1,460.3	1,038.4	886.3
D.R Horton, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Revenues									5,835.0	4,773.6	3,947.5
Unaudited Supplemental Consolidating Statement of Operations
Cost of sales									4,612.5	3,827.6	3,163.6
Selling, general and administrative expense									665.6	584.3	503.8
Goodwill impairment											0.0
Equity in earnings of unconsolidated entities									0.0
Gain on sale of assets									(2.4)		(4.5)
Other (income) expense									(6.0)	(8.3)	(3.1)
Income before income taxes									565.3	370.0	287.7
Income tax expense (benefit)									167.9	129.4	98.6
Equity in net income of subsidiaries, net of tax									1,069.7	798.2	700.6
Net income									1,467.1	1,038.8	889.7
Net income attributable to noncontrolling interests									0.0
Net income attributable to D.R. Horton, Inc.									1,467.1
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Revenues									9,795.7	8,939.5	7,930.3
Unaudited Supplemental Consolidating Statement of Operations
Cost of sales									7,752.5	7,199.6	6,357.5
Selling, general and administrative expense									676.1	631.0	592.7
Goodwill impairment											7.2
Equity in earnings of unconsolidated entities									0.0
Gain on sale of assets									0.0		0.0
Other (income) expense									(0.2)	(1.4)	(3.9)
Income before income taxes									1,367.3	1,110.3	976.8
Income tax expense (benefit)									406.1	388.6	334.9
Equity in net income of subsidiaries, net of tax									0.0	0.0	0.0
Net income									961.2	721.7	641.9
Net income attributable to noncontrolling interests									0.0
Net income attributable to D.R. Horton, Inc.									961.2
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Revenues									488.0	387.0	295.6
Unaudited Supplemental Consolidating Statement of Operations
Cost of sales									74.9	24.1	(7.7)
Selling, general and administrative expense									335.1	256.3	223.8
Goodwill impairment											0.0
Equity in earnings of unconsolidated entities									(5.3)
Gain on sale of assets									(16.4)		0.0
Other (income) expense									(39.1)	(15.8)	(14.7)
Income before income taxes									138.8	122.4	94.2
Income tax expense (benefit)									27.1	45.9	35.5
Equity in net income of subsidiaries, net of tax									0.0	0.0	0.0
Net income									111.7	76.5	58.7
Net income attributable to noncontrolling interests									3.1
Net income attributable to D.R. Horton, Inc.									108.6
Consolidation, Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Revenues									(50.7)	(9.1)	(16.0)
Unaudited Supplemental Consolidating Statement of Operations
Cost of sales									(41.8)	(8.5)	(10.8)
Selling, general and administrative expense									0.0	0.0	0.0
Goodwill impairment											0.0
Equity in earnings of unconsolidated entities									2.5
Gain on sale of assets									0.0		0.0
Other (income) expense									0.0	0.0	0.0
Income before income taxes									(11.4)	(0.6)	(5.2)
Income tax expense (benefit)									(3.4)	(0.2)	(1.8)
Equity in net income of subsidiaries, net of tax									(1,069.7)	(798.2)	(700.6)
Net income									(1,077.7)	(798.6)	(704.0)
Net income attributable to noncontrolling interests									(1.1)
Net income attributable to D.R. Horton, Inc.									$ (1,076.6)
Consolidation, Eliminations [Member] | D.R Horton, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Prior Period Reclassification Adjustment										$ 434.5	$ 370.4