Commitments and Contingencies - Legal Claims and Insurance (Details) - Homebuilding [Member] - USD ($) $ in Millions	6 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Rollforward of reserves for legal claims
Reserves for legal claims, beginning of period	$ 423.5	$ 451.0
Increase in reserves	56.2	0.5
Payments	(38.2)	(25.3)
Reserves for legal claims, end of period	$ 441.5	$ 426.2

Amount of loss contingency liability.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

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Amount of increase (decrease) in loss contingency liability.

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Amount of cash outflow reducing loss contingency liability.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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