Income Taxes - Deferred Tax Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Deferred tax assets:
Warranty and other reserves	$ 11,587	$ 11,559
Incentive compensation	18,993	17,368
Property, equipment and other assets	2,750	2,455
Federal and state tax carryforwards	357,146	383,508
Inventory adjustments	95,237	114,416
Uncertain tax positions	1,911	14,415
Other	3,923	3,052
Total deferred tax assets	491,547	546,773
Deferred tax liabilities:
Deferred revenues	(43,496)	(54,257)
Total deferred tax liabilities	(43,496)	(54,257)
Net deferred tax assets before valuation allowance	448,051	492,516
Valuation allowance	(445,228)	(487,263)
Net deferred tax assets	$ 2,823	$ 5,253