Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Mar. 31, 2013		Mar. 31, 2012		Sep. 30, 2012
Homebuilding revenues:
Consolidated revenues	$ 1,431.6		$ 961.2		$ 2,706.5		$ 1,867.8
Income (Loss) before Income Taxes
Income (loss) before income taxes	142.1	[1]	42.3	[1]	250.0	[1]	71.5	[1]
Homebuilding inventories
Total homebuilding inventory	5,324.1				5,324.1				4,165.2
Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	1,390.4		935.6		2,623.5		1,821.2
Income (Loss) before Income Taxes
Income (loss) before income taxes	127.4	[1]	34.6	[1]	217.6	[1]	59.7	[1]
Homebuilding inventories
Total homebuilding inventory	5,324.1	[2]			5,324.1	[2]			4,165.2	[2]
Financial Services [Member]
Homebuilding revenues:
Financial services revenues	41.2		25.6		83.0		46.6
Income (Loss) before Income Taxes
Income (loss) before income taxes	14.7	[1]	7.7	[1]	32.4	[1]	11.8	[1]
East [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	153.8		133.6		291.1		252.4
Income (Loss) before Income Taxes
Income (loss) before income taxes	8.5	[1]	3.6	[1]	15.5	[1]	6.2	[1]
Homebuilding inventories
Total homebuilding inventory	691.3	[2]			691.3	[2]			572.7	[2]
Midwest [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	92.8		71.7		182.2		129.4
Income (Loss) before Income Taxes
Income (loss) before income taxes	9.9	[1]	(1.0)	[1]	7.9	[1]	(8.1)	[1]
Homebuilding inventories
Total homebuilding inventory	376.1	[2]			376.1	[2]			318.1	[2]
Southeast [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	333.2		213.2		624.7		410.0
Income (Loss) before Income Taxes
Income (loss) before income taxes	28.3	[1]	8.7	[1]	47.7	[1]	15.5	[1]
Homebuilding inventories
Total homebuilding inventory	1,258.4	[2]			1,258.4	[2]			905.0	[2]
South Central [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	364.0		259.8		674.6		526.5
Income (Loss) before Income Taxes
Income (loss) before income taxes	32.4	[1]	13.0	[1]	57.6	[1]	28.4	[1]
Homebuilding inventories
Total homebuilding inventory	1,268.4	[2]			1,268.4	[2]			935.2	[2]
Southwest [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	79.0		55.6		154.9		109.6
Income (Loss) before Income Taxes
Income (loss) before income taxes	7.1	[1]	2.6	[1]	16.9	[1]	4.7	[1]
Homebuilding inventories
Total homebuilding inventory	234.6	[2]			234.6	[2]			188.6	[2]
West [Member] | Homebuilding [Member]
Homebuilding revenues:
Total homebuilding revenues	367.6		201.7		696.0		393.3
Income (Loss) before Income Taxes
Income (loss) before income taxes	41.2	[1]	7.7	[1]	72.0	[1]	13.0	[1]
Homebuilding inventories
Total homebuilding inventory	1,375.1	[2]			1,375.1	[2]			1,151.3	[2]
Corporate and Unallocated [Member] | Homebuilding [Member]
Homebuilding inventories
Total homebuilding inventory	$ 120.2	[2],[3]			$ 120.2	[2],[3]			$ 94.3	[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 revenue, while interest expense and 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 segment assets used by the Company’s chief operating decision maker.

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