Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended					6 Months Ended
	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
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
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 attributable to D.R. Horton, Inc.	$ 351.0			$ 229.2		$ 540.3	$ 436.1
Basic net income per common share attributable to D.R. Horton, Inc. (in dollars per share)	$ 0.93			$ 0.61		$ 1.44	$ 1.17
Weighted average number of common shares	376.8			374.4		376.3	373.8
Diluted net income per common share attributable to D.R. Horton, Inc. (in dollars per share)	$ 0.91			$ 0.60		$ 1.41	$ 1.15
Adjusted weighted average number of common shares	383.9			378.9		383.8	378.1
Cash dividends declared per common share (in dollars per share)	$ 0.125	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.25	$ 0.20