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, 2012		Sep. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	$ 68,470		$ 47,829
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	50,168		35,778
Money market instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	34,317		34,281
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	34,317	[1]	34,281	[1]
Available-for-sale securities | SMIC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	1,099		1,497
Available-for-sale securities | SMIC | 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	1,099	[2]	1,497	[2]
Available-for-sale securities | Nanya
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets measured at fair value	14,752
Available-for-sale securities | Nanya | 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	$ 14,752	[3]	$ 0	[3]

[1] Included in cash and cash equivalents

[2] Included in short-term investments

[3] Included in other assets