Net Periodic Pension Cost (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
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 830	$ 720	$ 1,660	$ 1,440
Interest Cost	984	962	1,967	1,925
Expected Return on Plan Assets	(1,100)	(770)	(2,200)	(1,540)
Recognized Actuarial Losses	892	598	1,785	1,195
Amortization of Prior Service Costs	15	17	31	35
Net Periodic Pension Cost	1,621	1,527	3,243	3,055
Supplemental Executive Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	204	110	408	220
Interest Cost	105	92	211	185
Recognized Actuarial Losses	94		188
Amortization of Prior Service Costs	105	105	210	210
Net Periodic Pension Cost	$ 508	$ 307	$ 1,017	$ 615