Contingencies - Litigation and Other Matters (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2016	Mar. 31, 2016	Sep. 30, 2015
DPA And HUD
Loss Contingencies [Line Items]
Company's liability under Deferred Prosecution Agreement (percent)	4.00%	4.00%
Maximum liability under the DPA and other settlement agreements	$ 48.0	$ 48.0
Portion of liability under DPA that has been paid as of balance sheet date		28.1
bzh_DeferredProsecutionAgreementAccrual	4.3	4.3
Loss Contingency Accrual, Provision	1.1	2.3
Legal Reserve
Loss Contingencies [Line Items]
Accrued amounts for litigation and other contingent liabilities	9.0	9.0	$ 12.6
Performance Bonds
Loss Contingencies [Line Items]
Letters of credit secured using cash collateral	43.2	43.2
Pledged Assets Separately Reported, Securities Pledged for Other Debt Obligations, at Fair Value	$ 213.7	$ 213.7

DPAandHUDAccrual

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- Definition

Company's Liability Under Deferred Prosecution Agreement, Percentage of Company's Adjusted EBITDA

+ References

No definition available.

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Amount of loss contingency liability.

+ References

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Amount charged against operating income increasing loss contingency liability, after adjustments to reduce previously estimated charges.

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- Definition

Amount of damages paid to the plaintiff in the legal matter.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

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The fair value, as of the date of each statement of financial position presented, of securities that are restricted as collateral for the payment of other debt obligations, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

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