Segment Information (Details) - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015
Homebuilding revenues:
Total revenues		$ 2,416.4	$ 2,302.6
Income Before Income Taxes
Income before income taxes	[1]	241.3	220.7
Homebuilding [Member]
Homebuilding revenues:
Homebuilding revenues		2,361.1	2,253.0
Inventory Impairments
Total inventory impairments		0.5	3.8
Income Before Income Taxes
Income before income taxes		229.0	206.1
Homebuilding Inventories
Total homebuilding inventories	[2]	8,088.2		$ 7,807.0
Financial Services [Member]
Homebuilding revenues:
Financial services revenues		55.3	49.6
Income Before Income Taxes
Income before income taxes		12.3	14.6
Operating Segments [Member] | Homebuilding [Member]
Homebuilding revenues:
Homebuilding revenues		2,361.1	2,253.0
Inventory Impairments
Total inventory impairments		0.5	3.8
Income Before Income Taxes
Income before income taxes	[1]	229.0	206.1
Operating Segments [Member] | Financial Services [Member]
Homebuilding revenues:
Financial services revenues		55.3	49.6
Income Before Income Taxes
Income before income taxes	[1]	12.3	14.6
Reportable Geographical Components [Member] | East [Member] | Homebuilding [Member]
Homebuilding revenues:
Homebuilding revenues		298.1	298.7
Inventory Impairments
Total inventory impairments		0.0	0.0
Income Before Income Taxes
Income before income taxes	[1]	27.7	26.3
Homebuilding Inventories
Total homebuilding inventories	[2]	812.1		817.3
Reportable Geographical Components [Member] | Midwest [Member] | Homebuilding [Member]
Homebuilding revenues:
Homebuilding revenues		123.3	130.0
Inventory Impairments
Total inventory impairments		0.0	0.0
Income Before Income Taxes
Income before income taxes	[1]	7.0	4.8
Homebuilding Inventories
Total homebuilding inventories	[2]	486.9		474.5
Reportable Geographical Components [Member] | Southeast [Member] | Homebuilding [Member]
Homebuilding revenues:
Homebuilding revenues		711.6	619.4
Inventory Impairments
Total inventory impairments		0.2	0.0
Income Before Income Taxes
Income before income taxes	[1]	76.9	58.0
Homebuilding Inventories
Total homebuilding inventories	[2]	1,931.5		1,876.7
Reportable Geographical Components [Member] | South Central [Member] | Homebuilding [Member]
Homebuilding revenues:
Homebuilding revenues		612.6	579.7
Inventory Impairments
Total inventory impairments		0.0	0.0
Income Before Income Taxes
Income before income taxes	[1]	64.7	61.2
Homebuilding Inventories
Total homebuilding inventories	[2]	1,999.6		1,909.0
Reportable Geographical Components [Member] | Southwest [Member] | Homebuilding [Member]
Homebuilding revenues:
Homebuilding revenues		73.9	75.4
Inventory Impairments
Total inventory impairments		0.0	0.0
Income Before Income Taxes
Income before income taxes	[1]	2.7	1.9
Homebuilding Inventories
Total homebuilding inventories	[2]	334.1		312.4
Reportable Geographical Components [Member] | West [Member] | Homebuilding [Member]
Homebuilding revenues:
Homebuilding revenues		541.6	549.8
Inventory Impairments
Total inventory impairments		0.3	3.8
Income Before Income Taxes
Income before income taxes	[1]	50.0	$ 53.9
Homebuilding Inventories
Total homebuilding inventories	[2]	2,261.0		2,165.3
Corporate and Unallocated [Member] | Homebuilding [Member]
Homebuilding Inventories
Total homebuilding inventories	[2],[3]	$ 263.0		$ 251.8

[1] Expenses maintained at the corporate level consist primarily of interest and property taxes, which are capitalized and amortized to cost of sales or expensed directly, and the expenses related to operating the Company’s corporate office. The amortization of capitalized interest and property taxes is allocated to each segment based on the segment’s cost of sales, while those expenses associated with the corporate office are allocated to each segment based on the segment’s inventory balances.

[2] Homebuilding inventories are the only assets included in the measure of homebuilding segment assets used by the Company’s chief operating decision makers.

[3] Corporate and unallocated consists primarily of capitalized interest and property taxes.