Valuation and Qualifying Accounts (Details) - Allowance For Doubtful Accounts Member - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period		$ 11,056	$ 12,934	$ 20,659
Charged to costs & expenses		12,269	10,414	15,923
Charged to other accounts		0	0	0
Valuation Allowances and Reserves, Deductions	[1]	12,460	12,292	23,648
Balance at end of period		$ 10,865	$ 11,056	$ 12,934

[1] Uncollectible accounts written off.