Magellan Acquisition - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Mar. 24, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017
Acquisition Date [Line Items]
Proceeds from term loan				$ 59,860
Cash consideration paid		$ 2,110
Goodwill		54,637	$ 54,926	$ 61,982
Goodwill impairment charge			6,628
Magellan [Member]
Acquisition Date [Line Items]
Total consideration paid	$ 67,874
Goodwill	40,591				$ 33,963
Goodwill impairment charge			$ 6,628
Magellan [Member] | Five - Year Term Loan [Member]
Acquisition Date [Line Items]
Proceeds from term loan	$ 60,000
Cash consideration paid		$ 2,100