Financial Assets Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Sep. 30, 2012
Assets:
Total	$ 19,177		$ 28,069
Cash equivalents
Assets:
Cash equivalents	13,681	[1]	644	[1]
U.S. corporate debt
Assets:
Marketable securities available-for-sale			2,008	[2]
U.S. government obligations
Assets:
Marketable securities available-for-sale			20,000	[2]
Marketable securities
Assets:
Marketable securities available-for-sale	5,496	[3]	5,417	[3]
Active Markets for Identical Instruments (Level 1)
Assets:
Total	19,177		6,061
Active Markets for Identical Instruments (Level 1) | Cash equivalents
Assets:
Cash equivalents	13,681	[1]	644	[1]
Active Markets for Identical Instruments (Level 1) | Marketable securities
Assets:
Marketable securities available-for-sale	5,496	[3]	5,417	[3]
Significant Other Observable Inputs (Level 2)
Assets:
Total			22,008
Significant Other Observable Inputs (Level 2) | U.S. corporate debt
Assets:
Marketable securities available-for-sale			2,008	[2]
Significant Other Observable Inputs (Level 2) | U.S. government obligations
Assets:
Marketable securities available-for-sale			$ 20,000	[2]

[1] Included in cash and cash equivalents on our balance sheet at December 31, 2012 and September 30, 2012. Not included in this table are cash deposits of $77.2 million and $71.0 million at December 31, 2012 and September 30, 2012, respectively.

[2] Included in current marketable securities on our balance sheet at September 30, 2012.

[3] 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 December 31, 2012 and September 30, 2012.