Net Periodic Benefit Cost for Period Reconciliation of Changes in Plan Assets Projected Benefit Obligations and Amounts Recognized in Other Comprehensive Income and Accumulated Other Comprehensive Income (Detail) - Frozen Defined Benefit Pension Plans - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Pension Plan Assets, Beginning Balance	$ 63,788	$ 65,379	$ 60,028
Net Periodic Pension Cost in Income Statement, Interest cost	2,622	2,762	2,761
Net Periodic Pension Cost in Income Statement, Actual return on plan assets	(8,595)	(679)	(7,614)
Net Periodic Pension Cost in Income Statement, Investment and other expenses	(362)	(577)	(262)
Net Periodic Pension Cost in Income Statement, Difference between actual and expected return on plan assets	5,579	(2,259)	4,472
Net Periodic Pension Cost in Income Statement, Anticipated expenses	319	327	300
Net Periodic Pension Cost in Income Statement, Amortization of unrecognized net actuarial loss	2,591	2,226	2,113
Net Periodic Pension Cost in Income Statement, Annual cost/change	2,154	1,800	1,770
Cash, Employer contributions/ Annual cost/change	(17)	(1,743)	(2,014)
Fair Value of Pension Plan Assets, Actual return on plan assets	8,595	679	7,614
Fair Value of Pension Plan Assets, Employer contributions	17	1,743	2,014
Fair Value of Pension Plan Assets, Benefit payments	(4,124)	(4,013)	(4,277)
Fair Value of Pension Plan Assets, Annual cost/change	4,488	(1,591)	5,351
Fair Value of Pension Plan Assets, Ending Balance	68,276	63,788	65,379
Projected Benefit Obligation, Beginning balance	(67,121)	(70,482)	(64,305)
Projected Benefit Obligation, Interest cost	(2,622)	(2,762)	(2,761)
Projected Benefit Obligation, Benefit payments	4,124	4,013	4,277
Projected Benefit Obligation, Investment and other expenses	362	577	262
Projected Benefit Obligation , Anticipated expenses	(319)	(327)	(300)
Projected Benefit Obligation, Actuarial gain (loss)	(5,103)	1,860	(7,655)
Projected Benefit Obligation , Annual cost/change	(3,558)	3,361	(6,177)
Projected Benefit Obligation, Ending balance	(70,679)	(67,121)	(70,482)
Funded status at the end of the year	(2,403)	(3,333)	(5,103)
Other Comprehensive (Income) / Loss, Difference between actual and expected return on plan assets	(5,579)	2,259	(4,472)
Other Comprehensive (Income) / Loss, Actuarial gain (loss)	5,103	(1,860)	7,655
Other Comprehensive (Income) / Loss, Amortization of unrecognized net actuarial loss	(2,591)	(2,226)	(2,113)
Other Comprehensive (Income) / Loss, Annual cost/change	(3,067)	(1,827)	1,070
Gross Pension Related Accumulated Other Comprehensive Income, Beginning Balance	24,771	26,598	25,528
Other Comprehensive (Income) / Loss, Annual cost/change	(3,067)	(1,827)	1,070
Gross Pension Related Accumulated Other Comprehensive Income, Ending Balance	$ 21,704	$ 24,771	$ 26,598