Employee Benefit Plans - Schedule of Changes in Components of Unrecognized Benefit Plan Costs (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Pension Plans [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net actuarial loss	$ 14,443	$ 9,179
Prior service costs
Net actuarial loss from previous years	(2,549)	(1,752)
Prior service costs	(63)	(61)
Income tax benefits related to above items	(4,732)
Changes in unrecognized benefit plan costs	7,099	7,366
Supplemental Employee Retirement Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net actuarial loss	2,867	106
Prior service costs
Prior service costs	(420)	(420)
Income tax benefits related to above items	(979)	(29)
Changes in unrecognized benefit plan costs	$ 1,468	$ (343)