Fair Value Measurements (Assets and Liabilities that are Measured at Fair Value on a Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	$ 53,330		$ 68,470
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	37,735		50,168
Money market instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	19,318		34,317
Money market instruments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	19,318	[1]	34,317	[1]
Available-for-sale securities | (SMIC) common stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	1,793		1,099
Available-for-sale securities | (SMIC) common stock | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	1,793	[2]	1,099	[2]
Available-for-sale securities | Nanya Technology Corporation (Nanya) common stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	16,624		14,752
Available-for-sale securities | Nanya Technology Corporation (Nanya) common stock | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	$ 16,624	[3]	$ 14,752	[3]

[1] Included in cash and cash equivalents

[2] Included in short-term investments

[3] Included in short-term investments at September 30, 2013 and in other assets at September 30, 2012