Contingencies - Narrative (Details) $ in Thousands	12 Months Ended			27 Months Ended
	Sep. 30, 2016 USD ($) home Community	Sep. 30, 2015 USD ($) Community	Sep. 30, 2014 USD ($) Community	Sep. 30, 2016 USD ($) home	Sep. 30, 2013 USD ($)
Loss Contingencies [Line Items]
Limited product warranty length	10 years
Accrued warranty expenses	$ 39,131	$ 27,681	$ 16,084	$ 39,131	$ 11,663
Insurance recoveries	59,300	18,900		78,200
Insurance receivables	30,700			$ 30,700
Excess insurance recovery	$ 3,600
Company's liability under deferred prosecution agreement, percentage of company's adjusted EBITDA	4.00%			4.00%
Accrued amounts for litigation and other contingent liabilities	$ 10,200	12,600		$ 10,200
DPA Liability
Loss Contingencies [Line Items]
Estimate of possible loss	48,000			48,000
Damages paid	28,100
Accrued amounts for litigation and other contingent liabilities	6,900			6,900
Expense related to DPA and HUD agreements	$ 4,900	5,300	$ 5,400
Florida
Loss Contingencies [Line Items]
Accrued warranty expenses		$ 14,500
Specific Warranty Issue
Loss Contingencies [Line Items]
Product warranty expense				80,400
Specific Warranty Issue | New Jersey
Loss Contingencies [Line Items]
Number of communities with water intrusion issues | Community	2	1	1
Product warranty expense	$ 1,200		$ 600	1,800
Specific Warranty Issue | Florida
Loss Contingencies [Line Items]
Product warranty expense	48,000	$ 26,300		78,600
Product warranty expense, net of insurance receivable		13,600	$ 4,300
Accrued warranty expenses	$ 22,600			$ 22,600
Numer of homes likely to require more than minor repairs | home	690			690
Change on number of homes likely to be repaired | home	158
Number of homes that have been repaired | home	437			437
Accrued product warranty, decrease for payments	$ 39,900
Estimated remaining warranty costs	4,700			$ 4,700
Insurance recoveries offset warranty expense		$ 12,700
Performance Bonds
Loss Contingencies [Line Items]
Letters of credit secured using cash collateral	50,300			50,300
Cash collateral in restricted accounts securing letters of credit	$ 207,600			$ 207,600
Minimum
Loss Contingencies [Line Items]
Standard product warranty period	1 year
Maximum
Loss Contingencies [Line Items]
Standard product warranty period	2 years
Settled Litigation | Insurance Settlement
Loss Contingencies [Line Items]
Insurance recoveries	$ 15,500