Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Mar. 31, 2015		Mar. 31, 2014		Sep. 30, 2014
Homebuilding revenues:
Consolidated revenues	$ 2,398.0		$ 1,735.0		$ 4,700.7		$ 3,405.6
Income (Loss) before Income Taxes
Income (loss) before income taxes	230.1	[1]	201.9	[1]	450.8	[1]	391.6	[1]
Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	2,338.5		1,696.6		4,591.5		3,332.3
Asset Impairment Charges [Abstract]
Inventory Write-down	8.1		2.3		12.0		2.3
Income (Loss) before Income Taxes
Income (loss) before income taxes	208.6	[1]	191.7	[1]	414.7	[1]	373.6	[1]
Homebuilding inventories
Total homebuilding inventory	8,136.9	[2]			8,136.9	[2]			7,700.5	[2]
Financial Services [Member]
Homebuilding revenues:
Financial Services Revenue	59.5		38.4		109.2		73.3
Income (Loss) before Income Taxes
Income (loss) before income taxes	21.5	[1]	10.2	[1]	36.1	[1]	18.0	[1]
East [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	280.7		203.2		579.5		393.3
Asset Impairment Charges [Abstract]
Inventory Write-down	0		0		0		0
Income (Loss) before Income Taxes
Income (loss) before income taxes	13.0	[1]	14.2	[1]	39.4	[1]	25.7	[1]
Homebuilding inventories
Total homebuilding inventory	888.5	[2]			888.5	[2]			842.7	[2]
Midwest [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	145.0		99.9		274.9		205.7
Asset Impairment Charges [Abstract]
Inventory Write-down	0		0		0		0
Income (Loss) before Income Taxes
Income (loss) before income taxes	10.2	[1]	9.1	[1]	15.0	[1]	19.1	[1]
Homebuilding inventories
Total homebuilding inventory	507.0	[2]			507.0	[2]			477.6	[2]
Southeast [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	646.1		471.3		1,265.5		918.7
Asset Impairment Charges [Abstract]
Inventory Write-down	7.3		2.1		7.3		2.1
Income (Loss) before Income Taxes
Income (loss) before income taxes	58.7	[1]	52.2	[1]	116.7	[1]	103.7	[1]
Homebuilding inventories
Total homebuilding inventory	2,030.4	[2]			2,030.4	[2]			1,943.0	[2]
South Central [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	628.2		430.4		1,207.9		851.5
Asset Impairment Charges [Abstract]
Inventory Write-down	0.7		0		0.7		0
Income (Loss) before Income Taxes
Income (loss) before income taxes	65.1	[1]	46.6	[1]	126.2	[1]	89.0	[1]
Homebuilding inventories
Total homebuilding inventory	1,927.7	[2]			1,927.7	[2]			1,742.5	[2]
Southwest [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	70.9		63.1		146.3		133.8
Asset Impairment Charges [Abstract]
Inventory Write-down	0		0		0		0
Income (Loss) before Income Taxes
Income (loss) before income taxes	1.2	[1]	5.5	[1]	3.1	[1]	11.5	[1]
Homebuilding inventories
Total homebuilding inventory	290.6	[2]			290.6	[2]			292.9	[2]
West [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	567.6		428.7		1,117.4		829.3
Asset Impairment Charges [Abstract]
Inventory Write-down	0.1		0.2		4.0		0.2
Income (Loss) before Income Taxes
Income (loss) before income taxes	60.4	[1]	64.1	[1]	114.3	[1]	124.6	[1]
Homebuilding inventories
Total homebuilding inventory	2,240.0	[2]			2,240.0	[2]			2,169.4	[2]
Corporate and Unallocated [Member] | Homebuilding [Member]
Homebuilding inventories
Total homebuilding inventory	$ 252.7	[2],[3]			$ 252.7	[2],[3]			$ 232.4	[2],[3]

[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.