Fair Value Measurements (Narrative) (Details) (USD $) Share data in Millions, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Write down of investment		$ 2,300,000
Purchases of available-for-sale securities	27,109,000		0	27,109,000	0
Foreign
Segment Reporting Information [Line Items]
Cash, cash equivalents and short term investments	39,300,000	39,300,000	71,200,000	39,300,000
China
Segment Reporting Information [Line Items]
Cash, cash equivalents and short term investments			4,700,000
Nanya
Segment Reporting Information [Line Items]
Available-for-sale Securities, Equity Securities Shares Sold During Period			143.5
Proceeds from Sale of Available-for-sale Securities, Equity			21,200,000
Available-for-sale Securities, Gross Realized Gains			$ 12,000,000