Accumulated Other Comprehensive Loss - Summary of Amounts Reclassified (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive loss	$ 76	$ 329
Net actuarial loss for pension benefit plans	888
Tax expense
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net loss (included within other income, net)	101	343	$ 1,303
Tax expense	(25)	(14)	(497)
Amounts reclassified from accumulated other comprehensive loss	$ 76	$ 329	$ 806