Supplemental Guarantor Information - Statement of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	$ 306.5	$ (185.7)
INVESTING ACTIVITIES
Expenditures for property and equipment	(110.1)	(103.5)
Proceeds from sale of assets	261.1	0.0
Increase in restricted cash	(42.2)	(9.9)
Investment in unconsolidated entities	(0.1)	0.0
Return of investment in unconsolidated entities	15.5	0.0
Net principal (increase) decrease of other mortgage loans and real estate owned	(0.8)	5.3
Purchases of debt securities collateralized by residential real estate	0.0	(8.8)
Intercompany advances	0.0	0.0
Payments related to business acquisitions, net of cash acquired	(158.1)	(4.1)
Net cash (used in) provided by investing activities	(34.7)	(121.0)
FINANCING ACTIVITIES
Proceeds from notes payable	2,164.3	700.0
Repayment of notes payable	(2,179.5)	(1,051.4)
Advances (payments) on mortgage repurchase facility, net	106.3	0.4
Intercompany advances	0.0	0.0
Proceeds from stock associated with certain employee benefit plans	36.2	34.3
Excess income tax benefit from employee stock awards	0.0	10.5
Cash paid for shares withheld for taxes	(10.3)	(5.1)
Cash dividends paid	(141.3)	(112.2)
Repurchases of common stock	(74.9)	(60.6)
Distributions to noncontrolling interests, net	(2.2)	0.0
Net cash (used in) provided by financing activities	(101.4)	(484.1)
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	170.4	(790.8)
Cash and cash equivalents at beginning of period	1,007.8	1,303.2
Cash and cash equivalents at end of period	1,178.2	512.4
Eliminations [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(62.0)	(75.0)
INVESTING ACTIVITIES
Expenditures for property and equipment	5.0	0.0
Proceeds from sale of assets	0.0
Increase in restricted cash	0.0	0.0
Investment in unconsolidated entities	0.0
Return of investment in unconsolidated entities	0.0
Net principal (increase) decrease of other mortgage loans and real estate owned	0.0	0.0
Purchases of debt securities collateralized by residential real estate		0.0
Intercompany advances	(615.7)	(187.3)
Payments related to business acquisitions, net of cash acquired	0.0	0.0
Net cash (used in) provided by investing activities	(610.7)	(187.3)
FINANCING ACTIVITIES
Proceeds from notes payable	0.0	0.0
Repayment of notes payable	0.0	0.0
Advances (payments) on mortgage repurchase facility, net	0.0	0.0
Intercompany advances	615.7	187.3
Proceeds from stock associated with certain employee benefit plans	0.0	0.0
Excess income tax benefit from employee stock awards		0.0
Cash paid for shares withheld for taxes	0.0	0.0
Cash dividends paid	57.0	75.0
Repurchases of common stock	0.0	0.0
Distributions to noncontrolling interests, net	0.0
Net cash (used in) provided by financing activities	672.7	262.3
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	0.0	0.0
Cash and cash equivalents at beginning of period	0.0	0.0
Cash and cash equivalents at end of period	0.0	0.0
D.R. Horton, Inc. [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(17.9)	(392.7)
INVESTING ACTIVITIES
Expenditures for property and equipment	(29.1)	(44.6)
Proceeds from sale of assets	0.0
Increase in restricted cash	(0.2)	(1.1)
Investment in unconsolidated entities	0.0
Return of investment in unconsolidated entities	0.0
Net principal (increase) decrease of other mortgage loans and real estate owned	0.0	0.0
Purchases of debt securities collateralized by residential real estate		(8.8)
Intercompany advances	615.7	187.3
Payments related to business acquisitions, net of cash acquired	(560.0)	(4.1)
Net cash (used in) provided by investing activities	26.4	128.7
FINANCING ACTIVITIES
Proceeds from notes payable	2,162.2	700.0
Repayment of notes payable	(2,165.2)	(1,050.0)
Advances (payments) on mortgage repurchase facility, net	0.0	0.0
Intercompany advances	0.0	0.0
Proceeds from stock associated with certain employee benefit plans	36.2	34.3
Excess income tax benefit from employee stock awards		10.5
Cash paid for shares withheld for taxes	(10.3)	(5.1)
Cash dividends paid	(141.3)	(112.2)
Repurchases of common stock	(74.9)	(60.6)
Distributions to noncontrolling interests, net	0.0
Net cash (used in) provided by financing activities	(193.3)	(483.1)
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(184.8)	(747.1)
Cash and cash equivalents at beginning of period	780.9	1,076.4
Cash and cash equivalents at end of period	596.1	329.3
Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	640.4	239.1
INVESTING ACTIVITIES
Expenditures for property and equipment	(21.5)	(18.8)
Proceeds from sale of assets	0.0
Increase in restricted cash	(1.8)	(0.3)
Investment in unconsolidated entities	0.0
Return of investment in unconsolidated entities	0.0
Net principal (increase) decrease of other mortgage loans and real estate owned	0.0	0.0
Purchases of debt securities collateralized by residential real estate		0.0
Intercompany advances	0.0	0.0
Payments related to business acquisitions, net of cash acquired	0.0	0.0
Net cash (used in) provided by investing activities	(23.3)	(19.1)
FINANCING ACTIVITIES
Proceeds from notes payable	0.0	0.0
Repayment of notes payable	(3.7)	(1.4)
Advances (payments) on mortgage repurchase facility, net	0.0	0.0
Intercompany advances	(660.6)	(282.8)
Proceeds from stock associated with certain employee benefit plans	0.0	0.0
Excess income tax benefit from employee stock awards		0.0
Cash paid for shares withheld for taxes	0.0	0.0
Cash dividends paid	0.0	0.0
Repurchases of common stock	0.0	0.0
Distributions to noncontrolling interests, net	0.0
Net cash (used in) provided by financing activities	(664.3)	(284.2)
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(47.2)	(64.2)
Cash and cash equivalents at beginning of period	154.5	154.0
Cash and cash equivalents at end of period	107.3	89.8
Non-Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(254.0)	42.9
INVESTING ACTIVITIES
Expenditures for property and equipment	(64.5)	(40.1)
Proceeds from sale of assets	261.1
Increase in restricted cash	(40.2)	(8.5)
Investment in unconsolidated entities	(0.1)
Return of investment in unconsolidated entities	15.5
Net principal (increase) decrease of other mortgage loans and real estate owned	(0.8)	5.3
Purchases of debt securities collateralized by residential real estate		0.0
Intercompany advances	0.0	0.0
Payments related to business acquisitions, net of cash acquired	401.9	0.0
Net cash (used in) provided by investing activities	572.9	(43.3)
FINANCING ACTIVITIES
Proceeds from notes payable	2.1	0.0
Repayment of notes payable	(10.6)	0.0
Advances (payments) on mortgage repurchase facility, net	106.3	0.4
Intercompany advances	44.9	95.5
Proceeds from stock associated with certain employee benefit plans	0.0	0.0
Excess income tax benefit from employee stock awards		0.0
Cash paid for shares withheld for taxes	0.0	0.0
Cash dividends paid	(57.0)	(75.0)
Repurchases of common stock	0.0	0.0
Distributions to noncontrolling interests, net	(2.2)
Net cash (used in) provided by financing activities	83.5	20.9
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	402.4	20.5
Cash and cash equivalents at beginning of period	72.4	72.8
Cash and cash equivalents at end of period	$ 474.8	$ 93.3