Supplemental Guarantor Information - Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2017	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2015
ASSETS
Cash and cash equivalents	$ 512.4	$ 1,303.2	$ 906.8	$ 1,383.8
Investments in subsidiaries	0.0	0.0
Property and equipment, net	282.8	195.4
Other assets	525.9	499.6
Intercompany receivables	0.0	0.0
Total assets	11,977.1	11,558.9
LIABILITIES & EQUITY
Accounts payable and other liabilities	1,613.9	1,494.6
Intercompany payables	0.0	0.0
Notes payable	2,926.5	3,271.3
Total liabilities	4,540.4	4,765.9
Stockholders’ equity	7,436.2	6,792.5
Noncontrolling interests	0.5	0.5
Total equity	7,436.7	6,793.0
Total liabilities and equity	11,977.1	11,558.9
Eliminations [Member]
ASSETS
Cash and cash equivalents	0.0	0.0	0.0	0.0
Investments in subsidiaries	(4,595.5)	(4,118.6)
Property and equipment, net	(5.2)	(5.2)
Other assets	0.0	0.0
Intercompany receivables	(1,422.0)	(1,604.5)
Total assets	(6,022.7)	(5,728.3)
LIABILITIES & EQUITY
Accounts payable and other liabilities	(1.8)	(1.8)
Intercompany payables	(1,422.0)	(1,604.5)
Notes payable	0.0	0.0
Total liabilities	(1,423.8)	(1,606.3)
Stockholders’ equity	(4,598.9)	(4,122.0)
Noncontrolling interests	0.0	0.0
Total equity	(4,598.9)	(4,122.0)
Total liabilities and equity	(6,022.7)	(5,728.3)
D.R. Horton, Inc. [Member]
ASSETS
Cash and cash equivalents	329.3	1,076.4	717.0	1,217.7
Investments in subsidiaries	4,595.5	4,118.6
Property and equipment, net	104.3	72.0
Other assets	204.9	168.7
Intercompany receivables	1,422.0	1,604.5
Total assets	10,393.5	10,029.0
LIABILITIES & EQUITY
Accounts payable and other liabilities	511.8	444.1
Intercompany payables	0.0	0.0
Notes payable	2,442.1	2,789.0
Total liabilities	2,953.9	3,233.1
Stockholders’ equity	7,439.6	6,795.9
Noncontrolling interests	0.0	0.0
Total equity	7,439.6	6,795.9
Total liabilities and equity	10,393.5	10,029.0
Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	89.8	154.0	99.1	94.6
Investments in subsidiaries	0.0	0.0
Property and equipment, net	58.4	49.9
Other assets	252.6	274.2
Intercompany receivables	0.0	0.0
Total assets	6,558.3	6,300.0
LIABILITIES & EQUITY
Accounts payable and other liabilities	967.7	933.1
Intercompany payables	1,139.2	1,417.1
Notes payable	11.0	9.3
Total liabilities	2,117.9	2,359.5
Stockholders’ equity	4,440.4	3,940.5
Noncontrolling interests	0.0	0.0
Total equity	4,440.4	3,940.5
Total liabilities and equity	6,558.3	6,300.0
Non-Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	93.3	72.8	$ 90.7	$ 71.5
Investments in subsidiaries	0.0	0.0
Property and equipment, net	125.3	78.7
Other assets	68.4	56.7
Intercompany receivables	0.0	0.0
Total assets	1,048.0	958.2
LIABILITIES & EQUITY
Accounts payable and other liabilities	136.2	119.2
Intercompany payables	282.8	187.4
Notes payable	473.4	473.0
Total liabilities	892.4	779.6
Stockholders’ equity	155.1	178.1
Noncontrolling interests	0.5	0.5
Total equity	155.6	178.6
Total liabilities and equity	1,048.0	958.2
Homebuilding [Member]
ASSETS
Cash and cash equivalents	460.8	1,271.8
Restricted cash	10.9	9.5
Inventories	9,554.0	8,340.9
Deferred income taxes	383.7	476.3
Property and equipment, net	179.6	139.5
Other assets	470.3	456.2
Goodwill	80.0	80.0
Total assets	11,139.3	10,774.2
LIABILITIES & EQUITY
Notes payable	2,453.1	2,798.3
Total liabilities	4,013.3	4,252.4
Homebuilding [Member] | Eliminations [Member]
ASSETS
Restricted cash	0.0	0.0
Inventories	0.0	0.0
Deferred income taxes	0.0	0.0
Goodwill	0.0	0.0
Homebuilding [Member] | D.R. Horton, Inc. [Member]
ASSETS
Restricted cash	8.5	7.4
Inventories	3,586.1	2,822.1
Deferred income taxes	142.9	159.3
Goodwill	0.0	0.0
Homebuilding [Member] | Guarantor Subsidiaries [Member]
ASSETS
Restricted cash	2.4	2.1
Inventories	5,837.2	5,425.7
Deferred income taxes	237.9	314.1
Goodwill	80.0	80.0
Homebuilding [Member] | Non-Guarantor Subsidiaries [Member]
ASSETS
Restricted cash	0.0	0.0
Inventories	130.7	93.1
Deferred income taxes	2.9	2.9
Goodwill	0.0	0.0
Financial Services and Other [Member]
ASSETS
Cash and cash equivalents	51.6	31.4
Property and equipment, net	103.2	55.9
Other assets	55.6	43.4
Mortgage loans held for sale	627.4	654.0
Total assets	837.8	784.7
LIABILITIES & EQUITY
Total liabilities	527.1	513.5
Financial Services and Other [Member] | Eliminations [Member]
ASSETS
Mortgage loans held for sale	0.0	0.0
Financial Services and Other [Member] | D.R. Horton, Inc. [Member]
ASSETS
Mortgage loans held for sale	0.0	0.0
Financial Services and Other [Member] | Guarantor Subsidiaries [Member]
ASSETS
Mortgage loans held for sale	0.0	0.0
Financial Services and Other [Member] | Non-Guarantor Subsidiaries [Member]
ASSETS
Mortgage loans held for sale	$ 627.4	$ 654.0