Business Segment Information - Restructuring liabilitiy and employee separation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Restructuring liability
Balance as of the beginning of the period	$ 649	$ 1,893
Accrued costs	2,468	1,852	$ 6,272
Cash payments	(2,142)	(3,096)
Balance as of the end of the period	$ 975	$ 649	$ 1,893