Supplemental Guarantor Information - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	$ (113.8)	$ (373.1)
INVESTING ACTIVITIES
Expenditures for property and equipment	(21.6)	(20.2)
Proceeds from sale of assets	62.8	10.4
Expenditures related to rental properties	(59.6)	(11.4)
Return of investment in unconsolidated entities	1.9	4.4
Net principal increase of other mortgage loans and real estate owned	(0.6)	(0.6)
Intercompany advances	0.0	0.0
Payments related to business acquisitions	0.7	293.0
Net cash (used in) provided by investing activities	(17.8)	(310.4)
FINANCING ACTIVITIES
Proceeds from notes payable	495.7	578.3
Repayment of notes payable	0.0	(276.1)
Advances (payments) on mortgage repurchase facility, net	(38.6)	(163.8)
Other Financing Activity - Intercompany Advances	0.0	0.0
Proceeds from stock associated with certain employee benefit plans	4.1	8.6
Cash paid for shares withheld for taxes	(17.3)	(4.1)
Cash dividends paid	(64.6)	(56.0)
Repurchases of common stock	(163.1)	(140.6)
Distributions to noncontrolling interests, net	(0.4)	(0.5)
Proceeds from (Payments for) Other Financing Activities	(2.3)	0.0
Net cash (used in) provided by financing activities	213.5	(54.2)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	81.9	(737.7)
Cash, cash equivalents and restricted cash at beginning of period	1,514.0	1,506.0
Cash, cash equivalents and restricted cash at end of period	1,595.9	768.3
Eliminations [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(55.8)	(25.0)
INVESTING ACTIVITIES
Expenditures for property and equipment	0.0	0.0
Proceeds from sale of assets	0.0	0.0
Expenditures related to rental properties	10.8	0.0
Return of investment in unconsolidated entities	0.0	0.0
Net principal increase of other mortgage loans and real estate owned	0.0	0.0
Intercompany advances	(20.7)	129.9
Payments related to business acquisitions	0.0	0.0
Net cash (used in) provided by investing activities	(9.9)	129.9
FINANCING ACTIVITIES
Proceeds from notes payable	0.0	0.0
Repayment of notes payable		0.0
Advances (payments) on mortgage repurchase facility, net	0.0	0.0
Other Financing Activity - Intercompany Advances	20.7	(129.9)
Proceeds from stock associated with certain employee benefit plans	0.0	0.0
Cash paid for shares withheld for taxes	0.0	0.0
Cash dividends paid	45.0	25.0
Repurchases of common stock	0.0	0.0
Distributions to noncontrolling interests, net	0.0	0.0
Proceeds from (Payments for) Other Financing Activities	0.0
Net cash (used in) provided by financing activities	65.7	(104.9)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	0.0	0.0
Cash, cash equivalents and restricted cash at beginning of period	0.0	0.0
Cash, cash equivalents and restricted cash at end of period	0.0	0.0
D.R. Horton, Inc. [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(67.2)	(137.6)
INVESTING ACTIVITIES
Expenditures for property and equipment	(8.6)	(10.2)
Proceeds from sale of assets	0.0	10.4
Expenditures related to rental properties	(7.3)	0.0
Return of investment in unconsolidated entities	0.0	0.0
Net principal increase of other mortgage loans and real estate owned	0.0	0.0
Intercompany advances	20.7	(129.9)
Payments related to business acquisitions	0.7	293.0
Net cash (used in) provided by investing activities	4.1	(422.7)
FINANCING ACTIVITIES
Proceeds from notes payable	495.7	578.3
Repayment of notes payable		(275.0)
Advances (payments) on mortgage repurchase facility, net	0.0	0.0
Other Financing Activity - Intercompany Advances	0.0	0.0
Proceeds from stock associated with certain employee benefit plans	4.1	8.6
Cash paid for shares withheld for taxes	(17.3)	(4.1)
Cash dividends paid	(64.6)	(56.0)
Repurchases of common stock	(163.1)	(140.6)
Distributions to noncontrolling interests, net	0.0	0.0
Proceeds from (Payments for) Other Financing Activities	(1.7)
Net cash (used in) provided by financing activities	253.1	111.2
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	190.0	(449.1)
Cash, cash equivalents and restricted cash at beginning of period	883.9	914.7
Cash, cash equivalents and restricted cash at end of period	1,073.9	465.6
Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(64.6)	(244.2)
INVESTING ACTIVITIES
Expenditures for property and equipment	(12.0)	(6.4)
Proceeds from sale of assets	0.0	0.0
Expenditures related to rental properties	(8.3)	0.0
Return of investment in unconsolidated entities	0.0	0.0
Net principal increase of other mortgage loans and real estate owned	0.0	0.0
Intercompany advances	0.0	0.0
Payments related to business acquisitions	0.0	0.0
Net cash (used in) provided by investing activities	(20.3)	(6.4)
FINANCING ACTIVITIES
Proceeds from notes payable	0.0	0.0
Repayment of notes payable		(1.1)
Advances (payments) on mortgage repurchase facility, net	0.0	0.0
Other Financing Activity - Intercompany Advances	(0.1)	125.7
Proceeds from stock associated with certain employee benefit plans	0.0	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	0.0
Proceeds from (Payments for) Other Financing Activities	0.0
Net cash (used in) provided by financing activities	(0.1)	124.6
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(85.0)	(126.0)
Cash, cash equivalents and restricted cash at beginning of period	117.1	160.7
Cash, cash equivalents and restricted cash at end of period	32.1	34.7
Non-Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	73.8	33.7
INVESTING ACTIVITIES
Expenditures for property and equipment	(1.0)	(3.6)
Proceeds from sale of assets	62.8	0.0
Expenditures related to rental properties	(54.8)	(11.4)
Return of investment in unconsolidated entities	1.9	4.4
Net principal increase of other mortgage loans and real estate owned	(0.6)	(0.6)
Intercompany advances	0.0	0.0
Payments related to business acquisitions	0.0	0.0
Net cash (used in) provided by investing activities	8.3	(11.2)
FINANCING ACTIVITIES
Proceeds from notes payable	0.0	0.0
Repayment of notes payable		0.0
Advances (payments) on mortgage repurchase facility, net	(38.6)	(163.8)
Other Financing Activity - Intercompany Advances	(20.6)	4.2
Proceeds from stock associated with certain employee benefit plans	0.0	0.0
Cash paid for shares withheld for taxes	0.0	0.0
Cash dividends paid	(45.0)	(25.0)
Repurchases of common stock	0.0	0.0
Distributions to noncontrolling interests, net	(0.4)	(0.5)
Proceeds from (Payments for) Other Financing Activities	(0.6)
Net cash (used in) provided by financing activities	(105.2)	(185.1)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(23.1)	(162.6)
Cash, cash equivalents and restricted cash at beginning of period	513.0	430.6
Cash, cash equivalents and restricted cash at end of period	$ 489.9	$ 268.0