Supplemental Guarantor Information - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	$ (33.3)	$ (1.5)
INVESTING ACTIVITIES
Purchases of property and equipment	(22.2)	(20.1)
Decrease (increase) in restricted cash	(6.0)	0.0
Net principal decrease (increase) of other mortgage loans and real estate owned	1.0	(2.1)
Intercompany advances	0.0	0.0
Payments related to acquisition of a business	(4.1)	0.0
Net cash provided by (used in) investing activities	(31.3)	(22.2)
FINANCING ACTIVITIES
Repayment of notes payable	(54.3)	(81.0)
Intercompany advances	0.0	0.0
Proceeds from stock associated with certain employee benefit plans	2.8	17.0
Excess income tax benefit from employee stock awards	0.5	2.2
Cash dividends paid	(37.3)	(29.6)
Net cash (used in) provided by financing activities	(88.3)	(91.4)
DECREASE IN CASH AND CASH EQUIVALENTS	(152.9)	(115.1)
Cash and cash equivalents at beginning of period	1,303.2	1,383.8
Cash and cash equivalents at end of period	1,150.3	1,268.7
Eliminations [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	(50.0)	(40.0)
INVESTING ACTIVITIES
Purchases of property and equipment	0.0	0.0
Decrease (increase) in restricted cash	0.0	0.0
Net principal decrease (increase) of other mortgage loans and real estate owned	0.0	0.0
Intercompany advances	(91.1)	66.4
Payments related to acquisition of a business	0.0
Net cash provided by (used in) investing activities	(91.1)	66.4
FINANCING ACTIVITIES
Repayment of notes payable	0.0	0.0
Intercompany advances	91.1	(66.4)
Proceeds from stock associated with certain employee benefit plans	0.0	0.0
Excess income tax benefit from employee stock awards	0.0	0.0
Cash dividends paid	50.0	40.0
Net cash (used in) provided by financing activities	141.1	(26.4)
DECREASE 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	(107.1)	35.7
INVESTING ACTIVITIES
Purchases of property and equipment	(10.5)	(10.6)
Decrease (increase) in restricted cash	0.4	0.1
Net principal decrease (increase) of other mortgage loans and real estate owned	0.0	0.0
Intercompany advances	91.1	(66.4)
Payments related to acquisition of a business	(4.1)
Net cash provided by (used in) investing activities	76.9	(76.9)
FINANCING ACTIVITIES
Repayment of notes payable	0.0	0.0
Intercompany advances	0.0	0.0
Proceeds from stock associated with certain employee benefit plans	2.8	17.0
Excess income tax benefit from employee stock awards	0.5	2.2
Cash dividends paid	(37.3)	(29.6)
Net cash (used in) provided by financing activities	(34.0)	(10.4)
DECREASE IN CASH AND CASH EQUIVALENTS	(64.2)	(51.6)
Cash and cash equivalents at beginning of period	1,076.4	1,217.7
Cash and cash equivalents at end of period	1,012.2	1,166.1
Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	40.5	(111.3)
INVESTING ACTIVITIES
Purchases of property and equipment	(5.4)	(4.7)
Decrease (increase) in restricted cash	0.3	(0.1)
Net principal decrease (increase) 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	0.0
Net cash provided by (used in) investing activities	(5.1)	(4.8)
FINANCING ACTIVITIES
Repayment of notes payable	(0.3)	(0.2)
Intercompany advances	(127.9)	55.9
Proceeds from stock associated with certain employee benefit plans	0.0	0.0
Excess income tax benefit from employee stock awards	0.0	0.0
Cash dividends paid	0.0	0.0
Net cash (used in) provided by financing activities	(128.2)	55.7
DECREASE IN CASH AND CASH EQUIVALENTS	(92.8)	(60.4)
Cash and cash equivalents at beginning of period	154.0	94.6
Cash and cash equivalents at end of period	61.2	34.2
Non-Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES
Net cash (used in) provided by operating activities	83.3	114.1
INVESTING ACTIVITIES
Purchases of property and equipment	(6.3)	(4.8)
Decrease (increase) in restricted cash	(6.7)	0.0
Net principal decrease (increase) of other mortgage loans and real estate owned	1.0	(2.1)
Intercompany advances	0.0	0.0
Payments related to acquisition of a business	0.0
Net cash provided by (used in) investing activities	(12.0)	(6.9)
FINANCING ACTIVITIES
Repayment of notes payable	(54.0)	(80.8)
Intercompany advances	36.8	10.5
Proceeds from stock associated with certain employee benefit plans	0.0	0.0
Excess income tax benefit from employee stock awards	0.0	0.0
Cash dividends paid	(50.0)	(40.0)
Net cash (used in) provided by financing activities	(67.2)	(110.3)
DECREASE IN CASH AND CASH EQUIVALENTS	4.1	(3.1)
Cash and cash equivalents at beginning of period	72.8	71.5
Cash and cash equivalents at end of period	$ 76.9	$ 68.4