Interest Rate Swap Agreement Amount of Gain (Loss) and Reclassification (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
Interest Rate Swaps [Line Items]
Interest Expense	$ 554		$ 2,591	$ 1,836		$ 5,230
Gains (Losses) on Effective Cash Flow Hedge
Interest Rate Swaps [Line Items]
Net current period other comprehensive income (loss)	(340)			(340)
Interest Rate Swap | Gains (Losses) on Effective Cash Flow Hedge | Reclassification out of Accumulated Other Comprehensive Income
Interest Rate Swaps [Line Items]
Interest Expense	$ 56	[1]		$ 56	[1]

[1] amounts in parenthesis represent a decrease to income