Per Share Data (Calculation of Basic and Diluted EPS) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended										12 Months Ended
	Sep. 30, 2012		Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011		Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Numerator for basic and diluted net income (loss) per share:
Net income (loss)	$ (13,246)	[1]	$ 3,137	$ 3,601	$ 3,790	$ 34,874	[2]	$ 8,090	$ 5,781	$ 7,212	$ (2,718)	$ 55,957	$ 42,196
Denominator for basic net income (loss) per share:
Weighted average common shares outstanding (in shares)											27,120	26,568	25,603
Dilutive stock options and awards (in shares)											0	1,740	1,438
Denominator for diluted net income (loss) per share (in shares)											27,120	28,308	27,041
Basic net income (loss) per share (in dollars per share)	$ (0.48)		$ 0.11	$ 0.13	$ 0.14	$ 1.31		$ 0.30	$ 0.22	$ 0.27	$ (0.10)	$ 2.11	$ 1.65
Diluted net income (loss) per share (in dollars per share)	$ (0.48)		$ 0.11	$ 0.12	$ 0.13	$ 1.23		$ 0.28	$ 0.20	$ 0.26	$ (0.10)	$ 1.98	$ 1.56

[1] In the September 2012 quarter, the Company recorded a charge of approximately $14.3 million for the impairment of certain tangible and intangible assets related to the acquisition of Si En and a charge of approximately $2.3 million to write-down its investment in SMIC due to the decline in fair market value being considered other than temporary.

[2] In the September 2011 quarter, the Company recorded an income tax benefit of approximately $28.1 million from the release of the valuation allowance for certain deferred tax assets.