Contingencies - Litigation and Other Matters (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Sep. 30, 2015
DPA And HUD
Loss Contingencies [Line Items]
Company's liability under Deferred Prosecution Agreement (percent)	4.00%
Maximum liability under the DPA and other settlement agreements	$ 48.0
Portion of liability under DPA that has been paid as of balance sheet date	28.1
bzh_DeferredProsecutionAgreementAccrual	8.6
Loss Contingency Accrual, Provision	1.2
Legal Reserve
Loss Contingencies [Line Items]
Accrued amounts for litigation and other contingent liabilities	13.6	$ 12.6
Performance Bonds
Loss Contingencies [Line Items]
Letters of credit secured using cash collateral	43.2
Pledged Assets Separately Reported, Securities Pledged for Other Debt Obligations, at Fair Value	$ 188.6