Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Movement in Valuation Allowances and Reserves
Balance at beginning of year	$ 3,946	$ 5,599	$ 6,992
Charged to costs and expenses	8,030	7,760	13,498
Other	(7,924)	(9,413)	(14,891)
Balance at end of year	$ 4,052	$ 3,946	$ 5,599