Retirement Benefit Plans - Changes in the Fair Value of Level 3 Defined Benefit Plan Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Changes in the fair value of the Company's Level 3 investments
Plan assets at beginning of year	$ 20,896	$ 22,110
Actual return on plan assets	2,061	117
Plan assets at end of year	21,344	20,896
Level 3
Changes in the fair value of the Company's Level 3 investments
Plan assets at beginning of year	2,045	2,102
Actual return on plan assets	126	76
Purchases and sales of plan assets, net	14	(133)
Plan assets at end of year	$ 2,185	$ 2,045