Financial Assets Measured at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $) In Thousands	Sep. 30, 2011		Sep. 30, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	$ 177,500		$ 155,527
Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	71,674		86,912
Active Markets for Identical Instruments (Level 1) | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	67,504	[1]	82,545	[1]
Active Markets for Identical Instruments (Level 1) | Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	4,170	[2]	4,367	[2]
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	105,826		68,615
Significant Other Observable Inputs (Level 2) | U.S. corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	1,529	[3]	2,981	[3]
Significant Other Observable Inputs (Level 2) | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	13,993	[3]
Significant Other Observable Inputs (Level 2) | U.S. government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	44,092	[3]	39,452	[3]
Significant Other Observable Inputs (Level 2) | U.S. municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	46,212	[3]	8,915	[3]
Significant Other Observable Inputs (Level 2) | Non U.S. corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale			17,267	[3]
Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	67,504	[1]	82,545	[1]
U.S. corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	1,529	[3]	2,981	[3]
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	13,993	[3]
U.S. government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	44,092	[3]	39,452	[3]
U.S. municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	46,212	[3]	8,915	[3]
Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	4,170	[2]	4,367	[2]
Non U.S. corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale			$ 17,267	[3]

[1] Included in cash and cash equivalents on our balance sheet at September 30, 2011 and September 30, 2010. Not included in this table are cash deposits of $68.2 million and $63.7 million at September 30, 2011 and September 30, 2010, respectively.

[2] Represents securities held under a supplemental retirement and savings plan for certain officers and senior management employees, which are distributed upon termination or retirement of the employees. Included in long-term marketable securities on our balance sheet at September 30, 2011 and 2010.

[3] Included in current marketable securities on our balance sheet at September 30, 2011 and 2010.