Supplemental Guarantor Information - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	$ (75.0)	$ (28.2)
INVESTING ACTIVITIES
Expenditures for property and equipment	(44.4)	(22.2)
Proceeds from sale of rental properties	24.8	0.0
Decrease (increase) in restricted cash	(37.2)	(6.0)
Investment in unconsolidated entities	(0.1)	0.0
Return of investment in unconsolidated entities	15.0	0.0
Net principal decrease of other mortgage loans and real estate owned	0.1	1.0
Intercompany advances	0.0	0.0
Payments related to acquisition of a business, net of cash acquired	(156.4)	(4.1)
Net cash (used in) provided by investing activities	(198.2)	(31.3)
FINANCING ACTIVITIES
Proceeds from notes payable	1,113.9	0.0
Repayment of notes payable	(825.8)	(0.3)
Advances (payments) on mortgage repurchase facility, net	(32.6)	(54.0)
Intercompany advances	0.0	0.0
Proceeds from stock associated with certain employee benefit plans	14.6	2.8
Excess income tax benefit from employee stock awards	0.0	0.5
Cash paid for shares withheld for taxes	(10.3)	(5.1)
Cash dividends paid	(47.0)	(37.3)
Repurchases of common stock	(25.4)	0.0
Distributions to noncontrolling interests, net	(1.7)	0.0
Net cash (used in) provided by financing activities	185.7	(93.4)
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(87.5)	(152.9)
Cash and cash equivalents at beginning of period	1,007.8	1,303.2
Cash and cash equivalents at end of period	920.3	1,150.3
Eliminations [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(32.0)	(50.0)
INVESTING ACTIVITIES
Expenditures for property and equipment	0.0	0.0
Proceeds from sale of rental properties	0.0
Decrease (increase) in restricted cash	0.0	0.0
Investment in unconsolidated entities	0.0
Return of investment in unconsolidated entities	0.0
Net principal decrease of other mortgage loans and real estate owned	0.0	0.0
Intercompany advances	(2.7)	(91.1)
Payments related to acquisition of a business, net of cash acquired	0.0	0.0
Net cash (used in) provided by investing activities	(2.7)	(91.1)
FINANCING ACTIVITIES
Proceeds from notes payable	0.0
Repayment of notes payable	0.0	0.0
Advances (payments) on mortgage repurchase facility, net	0.0	0.0
Intercompany advances	2.7	91.1
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	32.0	50.0
Repurchases of common stock	0.0
Distributions to noncontrolling interests, net	0.0
Net cash (used in) provided by financing activities	34.7	141.1
(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	(3.0)	(102.0)
INVESTING ACTIVITIES
Expenditures for property and equipment	(15.1)	(10.5)
Proceeds from sale of rental properties	0.0
Decrease (increase) in restricted cash	1.6	0.4
Investment in unconsolidated entities	0.0
Return of investment in unconsolidated entities	0.0
Net principal decrease of other mortgage loans and real estate owned	0.0	0.0
Intercompany advances	2.7	91.1
Payments related to acquisition of a business, net of cash acquired	(558.3)	(4.1)
Net cash (used in) provided by investing activities	(569.1)	76.9
FINANCING ACTIVITIES
Proceeds from notes payable	1,112.8
Repayment of notes payable	(815.2)	0.0
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	14.6	2.8
Excess income tax benefit from employee stock awards		0.5
Cash paid for shares withheld for taxes	(10.3)	(5.1)
Cash dividends paid	(47.0)	(37.3)
Repurchases of common stock	(25.4)
Distributions to noncontrolling interests, net	0.0
Net cash (used in) provided by financing activities	229.5	(39.1)
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(342.6)	(64.2)
Cash and cash equivalents at beginning of period	780.9	1,076.4
Cash and cash equivalents at end of period	438.3	1,012.2
Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(61.6)	40.5
INVESTING ACTIVITIES
Expenditures for property and equipment	(7.8)	(5.4)
Proceeds from sale of rental properties	0.0
Decrease (increase) in restricted cash	(0.6)	0.3
Investment in unconsolidated entities	0.0
Return of investment in unconsolidated entities	0.0
Net principal decrease of other mortgage loans and real estate owned	0.0	0.0
Intercompany advances	0.0	0.0
Payments related to acquisition of a business, net of cash acquired	0.0	0.0
Net cash (used in) provided by investing activities	(8.4)	(5.1)
FINANCING ACTIVITIES
Proceeds from notes payable	0.0
Repayment of notes payable	(0.6)	(0.3)
Advances (payments) on mortgage repurchase facility, net	0.0	0.0
Intercompany advances	(4.5)	(127.9)
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
Distributions to noncontrolling interests, net	0.0
Net cash (used in) provided by financing activities	(5.1)	(128.2)
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(75.1)	(92.8)
Cash and cash equivalents at beginning of period	154.5	154.0
Cash and cash equivalents at end of period	79.4	61.2
Non-Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	21.6	83.3
INVESTING ACTIVITIES
Expenditures for property and equipment	(21.5)	(6.3)
Proceeds from sale of rental properties	24.8
Decrease (increase) in restricted cash	(38.2)	(6.7)
Investment in unconsolidated entities	(0.1)
Return of investment in unconsolidated entities	15.0
Net principal decrease of other mortgage loans and real estate owned	0.1	1.0
Intercompany advances	0.0	0.0
Payments related to acquisition of a business, net of cash acquired	401.9	0.0
Net cash (used in) provided by investing activities	382.0	(12.0)
FINANCING ACTIVITIES
Proceeds from notes payable	1.1
Repayment of notes payable	(10.0)	0.0
Advances (payments) on mortgage repurchase facility, net	(32.6)	(54.0)
Intercompany advances	1.8	36.8
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	(32.0)	(50.0)
Repurchases of common stock	0.0
Distributions to noncontrolling interests, net	(1.7)
Net cash (used in) provided by financing activities	(73.4)	(67.2)
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	330.2	4.1
Cash and cash equivalents at beginning of period	72.4	72.8
Cash and cash equivalents at end of period	$ 402.6	$ 76.9