Retirement Benefit Plans - Fair Values of Defined Benefit Plan Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Amounts recognized in the consolidated balance sheets are:
Asset Amount	$ 21,344	$ 20,896	$ 22,110
Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	19,159	18,851
Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	2,185	2,045	$ 2,102
Large value
Amounts recognized in the consolidated balance sheets are:
Asset Amount	492	487
Large value | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Large value | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	492	487
Large value | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Large blend
Amounts recognized in the consolidated balance sheets are:
Asset Amount	9,593	9,268
Large blend | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Large blend | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	9,593	9,268
Large blend | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Large growth
Amounts recognized in the consolidated balance sheets are:
Asset Amount	503	515
Large growth | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Large growth | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	503	515
Large growth | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Mid blend
Amounts recognized in the consolidated balance sheets are:
Asset Amount	57	109
Mid blend | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Mid blend | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	57	109
Mid blend | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Small blend
Amounts recognized in the consolidated balance sheets are:
Asset Amount	56	102
Small blend | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Small blend | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	56	102
Small blend | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Foreign large blend
Amounts recognized in the consolidated balance sheets are:
Asset Amount	1,565	1,559
Foreign large blend | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Foreign large blend | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	1,565	1,559
Foreign large blend | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Diversified emerging markets
Amounts recognized in the consolidated balance sheets are:
Asset Amount	18	35
Diversified emerging markets | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Diversified emerging markets | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	18	35
Diversified emerging markets | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Inflation protected bond
Amounts recognized in the consolidated balance sheets are:
Asset Amount	537	489
Inflation protected bond | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Inflation protected bond | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	537	489
Inflation protected bond | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Intermediate term bond
Amounts recognized in the consolidated balance sheets are:
Asset Amount	7,747	7,538
Intermediate term bond | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Intermediate term bond | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	5,562	5,493
Intermediate term bond | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	2,185	2,045
High inflation bond
Amounts recognized in the consolidated balance sheets are:
Asset Amount	360	340
High inflation bond | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
High inflation bond | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	360	340
High inflation bond | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Emerging markets bonds
Amounts recognized in the consolidated balance sheets are:
Asset Amount	66	56
Emerging markets bonds | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Emerging markets bonds | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	66	56
Emerging markets bonds | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Short-term bonds
Amounts recognized in the consolidated balance sheets are:
Asset Amount	350	398
Short-term bonds | Level 1
Amounts recognized in the consolidated balance sheets are:
Asset Amount	0	0
Short-term bonds | Level 2
Amounts recognized in the consolidated balance sheets are:
Asset Amount	350	398
Short-term bonds | Level 3
Amounts recognized in the consolidated balance sheets are:
Asset Amount	$ 0	$ 0