Fair Value Measurements (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Segment Reporting Information [Line Items]
Proceeds from sale of Ralink			$ 0	$ 2,768,000	$ 3,216,000
Pretax gain on sale of Ralink					2,800,000
Write down of investment		2,300,000
Purchases of available-for-sale securities	27,109,000		27,109,000	0	0
Foreign Institutions
Segment Reporting Information [Line Items]
Cash, cash equivalents and short term investments	39,300,000	39,300,000	39,300,000	41,600,000
China
Segment Reporting Information [Line Items]
Cash, cash equivalents and short term investments	$ 3,400,000	$ 3,400,000	$ 3,400,000