Selected Quarterly Financial Information (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended									12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2011	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Operating Income (Loss) [Abstract]
Revenue	$ 43,738	$ 44,582	$ 42,247	$ 44,211	$ 43,091	$ 33,473	$ 42,277	$ 49,306		$ 174,778	$ 168,147	$ 163,781
Cost of revenue	37,458	35,189	35,381	34,076	37,718	29,429	34,444	38,358		142,104	139,949	145,955
Gross profit	6,280	9,393	6,866	10,135	5,373	4,044	7,833	10,948		32,674	28,198	17,826
Operating expense (income):
Selling, general, and administrative	10,059	7,843	6,911	7,972	6,705	7,039	6,771	6,904		32,785	27,419	34,861
Research and development	4,809	4,681	5,204	4,403	5,796	4,674	4,112	5,390		19,097	19,972	22,338
Flood-related insurance proceeds					0	0	(14,808)	(4,192)		0	(19,000)	(9,000)
Gain on sale of assets	(100)	0	0	0	0	0	(413)	0		(100)	(413)	(2,742)
Total operating expense	14,768	12,524	12,115	12,375	12,501	11,713	(4,338)	8,102		51,782	27,978	53,451
Operating (loss) income	(8,488)	(3,131)	(5,249)	(2,240)	(7,128)	(7,669)	12,171	2,846		(19,108)	220	(35,625)
Other income (expense):
Interest expense, net	(145)	(134)	(117)	(126)	(191)	(185)	(186)	(238)		(522)	(800)	(677)
Foreign exchange gain	(5)	5	(90)	100	95	181	(21)	101		10	356	45
Gain on sale of investment	0	0	17	290	4,800	0	0	0		307	0	0
Change in fair value of financial instruments	(5)	110	7	(78)	172	373	(267)	237		34	515	(69)
Other income	51	0	0	0	0	17	0	0		51	17	0
Total other (expense) income	(104)	(19)	(183)	186	4,876	386	(474)	100		(120)	4,888	(1,902)
(Loss) income before income taxes	(8,592)	(3,150)	(5,432)	(2,054)	(2,252)	(7,283)	11,697	2,946		(19,228)	5,108	(37,527)
Income tax benefit (expense)	24,080	0	0	0	0	0	0	(120)	(1,600)	24,080	(120)	(1,644)
Net income (loss)	$ 15,488	$ (3,150)	$ (5,432)	$ (2,054)	$ (2,252)	$ (7,283)	$ 11,697	$ 2,826		$ 4,852	$ 4,988	$ (39,171)
Earnings Per Share, Basic and Diluted [Abstract]
Net income (loss) per basic share	$ 0.50	$ (0.10)	$ (0.18)	$ (0.07)	$ (0.08)	$ (0.27)	$ 0.44	$ 0.11		$ 0.16	$ 0.19	$ (1.66)
Net income (loss) per diluted share	$ 0.50	$ (0.10)	$ (0.18)	$ (0.07)	$ (0.08)	$ (0.27)	$ 0.44	$ 0.11		$ 0.16	$ 0.19	$ (1.66)
Weighted-average number of basic shares outstanding	30,752	30,656	30,392	29,938	27,158	26,609	26,310	25,977		30,453	26,531	23,559
Weighted-average number of diluted shares outstanding	30,992	30,656	30,392	29,938	27,158	26,609	26,642	26,236		30,777	26,812	23,559