Contingencies - Warranty (Details)	3 Months Ended		6 Months Ended		12 Months Ended		21 Months Ended
	Mar. 31, 2016 USD ($) home	Mar. 31, 2015 USD ($)	Mar. 31, 2016 USD ($) home	Mar. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($) Community	Mar. 31, 2016 USD ($) home
Loss Contingencies [Line Items]
Standard product warranty length, minimum			1 year
Standard product warranty length, maximum			2 years
Limited product warranty length			5 years
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 28,913,000	$ 27,227,000	$ 27,681,000	$ 16,084,000	$ 16,084,000
Accruals for warranties issued	3,086,000	1,630,000	5,701,000	3,155,000
Changes in liability related to warranties existing in prior periods	20,053,000	6,524,000	30,653,000	20,754,000
Payments made	(11,149,000)	(6,587,000)	(23,132,000)	(11,199,000)
Balance at end of period	40,903,000	28,794,000	40,903,000	28,794,000	27,681,000	$ 16,084,000	$ 40,903,000
Insurance Recoveries	19,800,000		36,200,000	5,700,000			55,100,000
InsuranceReceivableNet	27,800,000		27,800,000				27,800,000
Excess Insurance Recovery			3,600,000
Specific Warranty Issue
Movement in Standard Product Warranty Accrual [Roll Forward]
Product warranty expense							61,000,000
Specific Warranty Issue | FLORIDA
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period			14,500,000
Balance at end of period	26,300,000		26,300,000		14,500,000		26,300,000
Product warranty expense	$ 19,600,000	$ 4,300,000	$ 28,600,000	$ 17,900,000	$ 26,300,000	4,300,000	$ 59,200,000
Homes likely to require more than minor repairs | home	680		680				680
Movement on Number of Homes Likely to be Repaired | home	148
Homes Have Been Repaired | home	279		279				279
Product warranty accrual, payments	$ 8,000,000		$ 16,800,000
Estimated Remaining Warranty Costs	7,000,000		7,000,000				$ 7,000,000
Specific Warranty Issue | NEW JERSEY
Movement in Standard Product Warranty Accrual [Roll Forward]
Product warranty expense	$ 300,000		$ 1,200,000			$ 600,000	$ 1,800,000
Number of Communities With Water Intrusion Issues			2			1