Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Summary of Components of Net Periodic Benefit Cost and Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income [Line Items]
Net loss	$ 1,226	$ 1,502
Amortization of net loss	(620)	(458)
Settlement loss	(8,937)
Total recognized in other comprehensive income	606	1,044	1,001
Total recognized in net periodic benefit cost and other comprehensive income	(7,012)	1,750
Defined Benefit Plan
Summary of Components of Net Periodic Benefit Cost and Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income [Line Items]
Total recognized in other comprehensive income	$ (8,331)	$ 1,044