Accumulated Other Comprehensive (Loss) Income - Summary of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 274,834	$ 274,728	$ 274,560	$ 269,324	$ 273,679	$ 273,713	$ 274,560	$ 273,713
Total other comprehensive (loss) income	(2,275)	(149)	(105)	(235)	271	187	(2,529)	223
Ending Balance	276,392	274,834	274,728	271,297	269,324	273,679	276,392	271,297
Net Unrealized Gain (Loss) on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(202)		137	413		428	137	428
Other comprehensive income (loss) before reclassifications	(2,933)			(565)			(3,363)	(584)
Amounts reclassified from accumulated other comprehensive income				(52)				(52)
Less tax effect	615			129			706	133
Total other comprehensive (loss) income	(2,318)			(488)			(2,657)	(503)
Ending Balance	(2,520)	(202)		(75)	413		(2,520)	(75)
Unrealized Losses on Retirement Plans [Member] | Pension Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(2,996)		(3,055)	(6,153)		(6,605)	(3,055)	(6,605)
Amounts reclassified from accumulated other comprehensive income	38			305			113	877
Less tax effect	(8)			(64)			(24)	(184)
Total other comprehensive (loss) income	30			241			89	693
Ending Balance	(2,966)	(2,996)		(5,912)	(6,153)		(2,966)	(5,912)
Unrealized Losses on Retirement Plans [Member] | SERP Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(155)		(181)	(205)		(226)	(181)	(226)
Amounts reclassified from accumulated other comprehensive income	17			14			49	42
Less tax effect	(4)			(2)			(10)	(9)
Total other comprehensive (loss) income	13			12			39	33
Ending Balance	(142)	(155)		(193)	(205)		(142)	(193)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(3,353)	(3,204)	(3,099)	(5,945)	(6,216)	(6,403)	(3,099)	(6,403)
Other comprehensive income (loss) before reclassifications	(2,933)			(565)			(3,363)	(584)
Amounts reclassified from accumulated other comprehensive income	55			267			162	867
Less tax effect	603			63			672	(60)
Total other comprehensive (loss) income	(2,275)	(149)	(105)	(235)	271	187	(2,529)	223
Ending Balance	$ (5,628)	$ (3,353)	$ (3,204)	$ (6,180)	$ (5,945)	$ (6,216)	$ (5,628)	$ (6,180)