Accumulated Other Comprehensive Income (Loss) - Summary of Activity in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 201,822	$ 191,397
Ending Balance	207,619	194,153
Defined Benefit Pension Plan [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(1,907)	(3,432)
Other comprehensive income (loss) before reclassifications	763
Amounts reclassified from accumulated other comprehensive income (loss)	110
Total other comprehensive income (loss)	873
Ending Balance	(1,034)	(3,432)
Unrealized Gains (Losses) on Securities Available for Sale [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	1,962	3,167
Other comprehensive income (loss) before reclassifications	(843)	(178)
Total other comprehensive income (loss)	(843)	(178)
Ending Balance	1,119	2,989
Derivatives [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	627	(3,791)
Other comprehensive income (loss) before reclassifications	1,690	410
Amounts reclassified from accumulated other comprehensive income (loss)	187	527
Total other comprehensive income (loss)	1,877	937
Ending Balance	2,504	(2,854)
Accumulated Other Comprehensive Income/(Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	682	(4,056)
Other comprehensive income (loss) before reclassifications	1,610	232
Amounts reclassified from accumulated other comprehensive income (loss)	297	527
Total other comprehensive income (loss)	1,907	759
Ending Balance	$ 2,589	$ (3,297)