Allowance for Doubtful Accounts (Details) - Allowance for Doubtful Accounts - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Change in the allowance for doubtful accounts
Balance at beginning of period	$ 1,162	$ 1,752	$ 2,556
Bad debt expense	1,939	2,282	1,175
Uncollected accounts written off, net of recoveries	(1,694)	(2,872)	(1,979)
Balance at end of period	$ 1,407	$ 1,162	$ 1,752