Supplementary Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of year	$ 3,730	$ 5,009	$ 2,846
Provision / (Reversal)	(720)	1,698	(194)
Write offs	(1,249)	(1,942)	(130)
Acquired through business acquisitions	0	0	1,397
Adjustment	(895)	(1,035)	1,090
Balance at end of year	$ 866	$ 3,730	$ 5,009