Debt - Interest Rate Swap Contracts as Reflected on Balance Sheet (Details) - Designated as Hedging Instrument - Interest Rate Swaps - USD ($) $ in Thousands	Jun. 30, 2019	Sep. 30, 2018
Derivatives, Fair Value [Line Items]
Total derivatives	$ 775	$ 11,309
Current assets: Other Current Assets
Derivatives, Fair Value [Line Items]
Assets derivatives	821	3,867
Long-term assets: Other Assets
Derivatives, Fair Value [Line Items]
Assets derivatives	637	7,442
Current Liabilities: Other Current Liabilities
Derivatives, Fair Value [Line Items]
Liability derivatives	(222)	0
Long-Term Liabilities: Other Liabilities
Derivatives, Fair Value [Line Items]
Liability derivatives	$ (461)	$ 0

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