Fair Value of Financial Instruments - Location and Fair Value Amounts of Financial Instruments (Details) - Designated as hedging instrument - Interest rate swap - Cash flow hedging - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Other current assets
Derivative [Line Items]
Derivative liability, fair value, gross liability	$ 300	$ 0
Other assets
Derivative [Line Items]
Derivative liability, fair value, gross liability	400	0
Accrued expenses and other current liabilities
Derivative [Line Items]
Derivative liability, fair value, gross liability	0	2,462
Other liabilities
Derivative [Line Items]
Derivative liability, fair value, gross liability	$ 0	$ 903