Changes in Accumulated Other Comprehensive Income (Loss) by Component, Net of Income Tax (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Other Comprehensive Income (Loss) [Line Items]
Balance, September 30, 2012			$ (32,037)
Other comprehensive income (loss) before reclassifications			(204)
Amounts reclassified from accumulated other comprehensive income (loss)			1,362
Net current period other comprehensive income (loss)	494	566	1,158	807
Balance, March 31, 2013	(30,879)		(30,879)
Gains (Losses) on Defined Benefit Plan Items
Other Comprehensive Income (Loss) [Line Items]
Balance, September 30, 2012			(32,037)
Amounts reclassified from accumulated other comprehensive income (loss)			1,328
Net current period other comprehensive income (loss)			1,328
Balance, March 31, 2013	(30,709)		(30,709)
Gains (Losses) on Effective Cash Flow Hedge
Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications			(204)
Amounts reclassified from accumulated other comprehensive income (loss)			34
Net current period other comprehensive income (loss)			(170)
Balance, March 31, 2013	$ (170)		$ (170)