Supplemental Guarantor Information - Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Consolidating Statement of Operations
Revenues	$ 3,794.7	$ 3,251.3	$ 7,127.6	$ 6,155.5
Cost of sales	2,961.6	2,549.9	5,541.8	4,817.8
Selling, general and administrative expense	400.9	355.2	785.1	681.0
Equity in earnings of unconsolidated entities	(0.4)	0.0	(2.7)	0.0
Gain on sale of assets	(1.1)	0.0	(14.5)	0.0
Other (income) expense	(11.1)	(7.7)	(18.2)	(15.4)
Income before income taxes	444.8	353.9	836.1	672.1
Income tax expense	94.0	124.7	296.4	236.0
Equity in net income of subsidiaries, net of tax	0.0	0.0	0.0	0.0
Net income	350.8	229.2	539.7	436.1
Net loss attributable to noncontrolling interests	(0.2)	0.0	(0.6)	0.0
Net Income (Loss) Attributable to Parent	351.0	229.2	540.3	436.1
Eliminations [Member]
Consolidating Statement of Operations
Revenues	(13.5)	0.0	(13.5)	0.0
Cost of sales	(10.9)	0.0	(10.9)	0.0
Selling, general and administrative expense	0.0	0.0	0.0	0.0
Equity in earnings of unconsolidated entities	0.0		0.0
Gain on sale of assets	0.0		0.0
Other (income) expense	0.0	0.0	0.0	0.0
Income before income taxes	(2.6)	0.0	(2.6)	0.0
Income tax expense	0.0	0.0	0.0	0.0
Equity in net income of subsidiaries, net of tax	(267.5)	(181.0)	(410.8)	(346.8)
Net income	(270.1)	(181.0)	(413.4)	(346.8)
Net loss attributable to noncontrolling interests	0.0		0.0
Net Income (Loss) Attributable to Parent	(270.1)		(413.4)
D.R. Horton, Inc. [Member]
Consolidating Statement of Operations
Revenues	1,288.0	1,094.4	2,451.9	2,012.5
Cost of sales	1,026.2	877.9	1,941.6	1,613.3
Selling, general and administrative expense	156.9	143.3	309.1	267.2
Equity in earnings of unconsolidated entities	0.0		0.0
Gain on sale of assets	0.0		0.0
Other (income) expense	(1.7)	(1.1)	(2.1)	(5.2)
Income before income taxes	106.6	74.3	203.3	137.2
Income tax expense	20.7	26.1	71.8	47.9
Equity in net income of subsidiaries, net of tax	267.5	181.0	410.8	346.8
Net income	353.4	229.2	542.3	436.1
Net loss attributable to noncontrolling interests	0.0		0.0
Net Income (Loss) Attributable to Parent	353.4		542.3
D.R. Horton, Inc. [Member] | Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Prior Period Reclassification Adjustment		98.6		188.1
Guarantor Subsidiaries [Member]
Consolidating Statement of Operations
Revenues	2,402.7	2,044.6	4,455.1	3,940.7
Cost of sales	1,926.9	1,647.3	3,567.0	3,172.0
Selling, general and administrative expense	164.8	149.5	316.4	292.9
Equity in earnings of unconsolidated entities	0.0		0.0
Gain on sale of assets	0.0		0.0
Other (income) expense	(0.7)	(0.9)	(0.7)	(0.9)
Income before income taxes	311.7	248.7	572.4	476.7
Income tax expense	67.4	87.1	205.3	166.4
Equity in net income of subsidiaries, net of tax	0.0	0.0	0.0	0.0
Net income	244.3	161.6	367.1	310.3
Net loss attributable to noncontrolling interests	0.0		0.0
Net Income (Loss) Attributable to Parent	244.3		367.1
Non-Guarantor Subsidiaries [Member]
Consolidating Statement of Operations
Revenues	117.5	112.3	234.1	202.3
Cost of sales	19.4	24.7	44.1	32.5
Selling, general and administrative expense	79.2	62.4	159.6	120.9
Equity in earnings of unconsolidated entities	(0.4)		(2.7)
Gain on sale of assets	(1.1)		(14.5)
Other (income) expense	(8.7)	(5.7)	(15.4)	(9.3)
Income before income taxes	29.1	30.9	63.0	58.2
Income tax expense	5.9	11.5	19.3	21.7
Equity in net income of subsidiaries, net of tax	0.0	0.0	0.0	0.0
Net income	23.2	$ 19.4	43.7	$ 36.5
Net loss attributable to noncontrolling interests	(0.2)		(0.6)
Net Income (Loss) Attributable to Parent	$ 23.4		$ 44.3