Components of Net Deferred Income Tax Asset (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Deferred income tax assets:
Allowance for doubtful accounts	$ 784	$ 766	$ 702
Inventories	11,265	5,110	4,316
Net operating loss carry-forwards, tax credits and deferrals	16,293	6,823	2,270
Stock-based compensation	2,147	1,905	1,690
Accrued product warranty	176	134	809
Accrued compensated absences	419	467	520
Property and equipment	430		101
Insurance and other reserves	134	170	105
Deferred Tax Assets, Gross, Total	31,648	15,375	10,513
Deferred income tax liabilities:
Allowance for doubtful accounts	(9)		31
Property, plant and equipment and other	(3,158)	(7,481)	(6,034)
Subtotal deferred income tax assets	28,481	7,894	4,510
Valuation allowance	(28,259)	(7,715)	0
Net deferred income tax assets	222	179	4,510
U. S.
Deferred income tax assets:
Allowance for doubtful accounts	777	715	681
Inventories	11,215	5,089	4,350
Net operating loss carry-forwards, tax credits and deferrals	11,803	3,000
Stock-based compensation	2,147	1,905	1,690
Accrued product warranty	174	130	803
Accrued compensated absences	419	467	520
Property and equipment			101
Insurance and other reserves	127	170	62
Deferred Tax Assets, Gross, Total	26,662	11,476	8,207
Deferred income tax liabilities:
Allowance for doubtful accounts			31
Property, plant and equipment and other	(3,087)	(7,470)	(5,264)
Subtotal deferred income tax assets	23,575	4,006	2,974
Valuation allowance	(23,575)	(4,006)	0
Net deferred income tax assets			2,974
Non U. S.
Deferred income tax assets:
Allowance for doubtful accounts	7	51	21
Inventories	50	21	(34)
Net operating loss carry-forwards, tax credits and deferrals	4,490	3,823	2,270
Accrued product warranty	2	4	6
Property and equipment	430
Insurance and other reserves	7		43
Deferred Tax Assets, Gross, Total	4,986	3,899	2,306
Deferred income tax liabilities:
Allowance for doubtful accounts	(9)
Property, plant and equipment and other	(71)	(11)	(770)
Subtotal deferred income tax assets	4,906	3,888	1,536
Valuation allowance	(4,684)	(3,709)	0
Net deferred income tax assets	$ 222	$ 179	$ 1,536