Retirement Benefit Plans - Asset Allocation of Defined Benefit Pension Plan Assets and Fair Values and Levels in Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 17,937	$ 23,211	$ 21,609
Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	16,108	21,103
Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,829	2,108	$ 2,098
Large value
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	393	514
Large value | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	393	514
Large value | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Large blend
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	7,637	10,227
Large blend | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	7,637	10,227
Large blend | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Large growth
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	302	519
Large growth | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	302	519
Large growth | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Mid blend
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	167	223
Mid blend | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	167	223
Mid blend | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Small blend
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	359	697
Small blend | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	359	697
Small blend | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Foreign large blend
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,276	1,807
Foreign large blend | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,276	1,807
Foreign large blend | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Diversified emerging markets
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	63	86
Diversified emerging markets | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	63	86
Diversified emerging markets | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Inflation protected bond
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	971	1,087
Inflation protected bond | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	971	1,087
Inflation protected bond | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Intermediate term bond
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	6,332	7,396
Intermediate term bond | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	4,503	5,288
Intermediate term bond | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,829	2,108
High inflation bond
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	78	189
High inflation bond | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	78	189
High inflation bond | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Emerging markets bonds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value		164
Emerging markets bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value		164
Emerging markets bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value		0
Short-term bonds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	359	302
Short-term bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	359	302
Short-term bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 0	$ 0