Gross Unrealized Losses and Fair Value of Investments (Detail) (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Investments, Unrealized Loss Position [Line Items]
Fair Value	$ 22,529
Unrealized Losses	(7)
Fair Value
Unrealized Losses
Fair Value	22,529
Unrealized Losses	(7)
Commercial Paper
Investments, Unrealized Loss Position [Line Items]
Fair Value	18,993
Unrealized Losses	(4)
Fair Value
Unrealized Losses
Fair Value	18,993
Unrealized Losses	(4)
U.S. government obligations
Investments, Unrealized Loss Position [Line Items]
Fair Value	2,008
Unrealized Losses	(1)
Fair Value
Unrealized Losses
Fair Value	2,008
Unrealized Losses	(1)
Non U.S. corporate debt
Investments, Unrealized Loss Position [Line Items]
Fair Value	1,528	2,255
Unrealized Losses	(2)	(3)
Fair Value
Unrealized Losses
Fair Value	1,528	2,255
Unrealized Losses	$ (2)	$ (3)

Investments, Unrealized Loss Position [Line Items]

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This item represents the excess of amortized cost basis over fair value of securities that have been in a loss position for twelve months or longer for those securities which are categorized neither as held-to-maturity nor trading securities.

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This item represents the excess of amortized cost basis over fair value of securities in a loss position and which are categorized neither as held-to-maturity nor trading securities.

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