Fair Value Measurements (Marketable Equity and Cash Equivalents (Classified as Available-for-sale) and Cost Method Investments) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 43,112	$ 70,305
Gross Unrealized Holding Gains	10,218	0
Gross Unrealized Holding Losses	0	(1,835)
Fair Value	53,330	68,470
Money market instruments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,318	34,317
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Fair Value	19,318	34,317
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,595	18,302
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Fair Value	15,595	18,302
Available-for-sale securities | SMIC
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,099	1,099
Gross Unrealized Holding Gains	694	0
Gross Unrealized Holding Losses	0	0
Fair Value	1,793	1,099
Available-for-sale securities | Nanya
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,100	16,587
Gross Unrealized Holding Gains	9,524	0
Gross Unrealized Holding Losses	0	(1,835)
Fair Value	16,624	14,752
Amounts included in cash and cash equivalents
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	31,772	47,177
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Fair Value	31,772	47,177
Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,340	23,128
Gross Unrealized Holding Gains	10,218	0
Gross Unrealized Holding Losses	0	(1,835)
Fair Value	$ 21,558	$ 21,293