Supplemental Guarantor Information - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	$ (373.1)	$ (75.0)
INVESTING ACTIVITIES
Expenditures for property and equipment	(20.2)	(25.3)
Proceeds from sale of assets	10.4	24.8
Expenditures related to multi-family rental properties	(11.4)	(19.1)
Return of investment in unconsolidated entities	4.4	14.9
Net principal (increase) decrease of other mortgage loans and real estate owned	(0.6)	0.1
Intercompany advances	0.0	0.0
Payments related to business acquisitions, net of cash acquired	(293.0)	(156.4)
Net cash (used in) provided by investing activities	(310.4)	(161.0)
FINANCING ACTIVITIES
Proceeds from notes payable	578.3	1,113.9
Repayment of notes payable	(276.1)	(825.8)
Advances (payments) on mortgage repurchase facility, net	(163.8)	(32.6)
Intercompany advances	0.0	0.0
Proceeds from stock associated with certain employee benefit plans	8.6	14.6
Cash paid for shares withheld for taxes	(4.1)	(10.3)
Cash dividends paid	(56.0)	(47.0)
Repurchases of common stock	(140.6)	(25.4)
Distributions to noncontrolling interests, net	(0.5)	(1.7)
Net cash (used in) provided by financing activities	(54.2)	185.7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(737.7)	(50.3)
Cash, cash equivalents and restricted cash at beginning of period	1,506.0	1,024.3
Cash, cash equivalents and restricted cash at end of period	768.3	974.0
Eliminations [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(25.0)	(32.0)
INVESTING ACTIVITIES
Expenditures for property and equipment	0.0	0.0
Proceeds from sale of assets	0.0	0.0
Expenditures related to multi-family rental properties	0.0	0.0
Return of investment in unconsolidated entities	0.0	0.0
Net principal (increase) decrease of other mortgage loans and real estate owned	0.0	0.0
Intercompany advances	129.9	(2.7)
Payments related to business acquisitions, net of cash acquired	0.0	0.0
Net cash (used in) provided by investing activities	129.9	(2.7)
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	(129.9)	2.7
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	25.0	32.0
Repurchases of common stock	0.0	0.0
Distributions to noncontrolling interests, net	0.0	0.0
Net cash (used in) provided by financing activities	(104.9)	34.7
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	(137.6)	(3.0)
INVESTING ACTIVITIES
Expenditures for property and equipment	(10.2)	(15.1)
Proceeds from sale of assets	10.4	0.0
Expenditures related to multi-family rental properties	0.0	0.0
Return of investment in unconsolidated entities	0.0	0.0
Net principal (increase) decrease of other mortgage loans and real estate owned	0.0	0.0
Intercompany advances	(129.9)	2.7
Payments related to business acquisitions, net of cash acquired	(293.0)	(558.3)
Net cash (used in) provided by investing activities	(422.7)	(570.7)
FINANCING ACTIVITIES
Proceeds from notes payable	578.3	1,112.8
Repayment of notes payable	(275.0)	(815.2)
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	8.6	14.6
Cash paid for shares withheld for taxes	(4.1)	(10.3)
Cash dividends paid	(56.0)	(47.0)
Repurchases of common stock	(140.6)	(25.4)
Distributions to noncontrolling interests, net	0.0	0.0
Net cash (used in) provided by financing activities	111.2	229.5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(449.1)	(344.2)
Cash, cash equivalents and restricted cash at beginning of period	914.7	788.7
Cash, cash equivalents and restricted cash at end of period	465.6	444.5
Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(244.2)	(61.6)
INVESTING ACTIVITIES
Expenditures for property and equipment	(6.4)	(7.8)
Proceeds from sale of assets	0.0	0.0
Expenditures related to multi-family rental properties	0.0	0.0
Return of investment in unconsolidated entities	0.0	0.0
Net principal (increase) decrease of other mortgage loans and real estate owned	0.0	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	(6.4)	(7.8)
FINANCING ACTIVITIES
Proceeds from notes payable	0.0	0.0
Repayment of notes payable	(1.1)	(0.6)
Advances (payments) on mortgage repurchase facility, net	0.0	0.0
Intercompany advances	125.7	(4.5)
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
Net cash (used in) provided by financing activities	124.6	(5.1)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(126.0)	(74.5)
Cash, cash equivalents and restricted cash at beginning of period	160.7	156.0
Cash, cash equivalents and restricted cash at end of period	34.7	81.5
Non-Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	33.7	21.6
INVESTING ACTIVITIES
Expenditures for property and equipment	(3.6)	(2.4)
Proceeds from sale of assets	0.0	24.8
Expenditures related to multi-family rental properties	(11.4)	(19.1)
Return of investment in unconsolidated entities	4.4	14.9
Net principal (increase) decrease of other mortgage loans and real estate owned	(0.6)	0.1
Intercompany advances	0.0	0.0
Payments related to business acquisitions, net of cash acquired	0.0	401.9
Net cash (used in) provided by investing activities	(11.2)	420.2
FINANCING ACTIVITIES
Proceeds from notes payable	0.0	1.1
Repayment of notes payable	0.0	(10.0)
Advances (payments) on mortgage repurchase facility, net	(163.8)	(32.6)
Intercompany advances	4.2	1.8
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	(25.0)	(32.0)
Repurchases of common stock	0.0	0.0
Distributions to noncontrolling interests, net	(0.5)	(1.7)
Net cash (used in) provided by financing activities	(185.1)	(73.4)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(162.6)	368.4
Cash, cash equivalents and restricted cash at beginning of period	430.6	79.6
Cash, cash equivalents and restricted cash at end of period	$ 268.0	$ 448.0