Cash and Equivalents - Components of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Sep. 30, 2016	Jun. 30, 2016	Oct. 01, 2015
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 55,253	$ 47,226	$ 45,803	$ 49,973
Overnight Repurchase Agreements [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	6,369	9,988
Institutional Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	20,059	10,020
Cash [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	28,825	27,218
Cash and Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	1,000	1,000
Cash and Equivalents [Member] | Other Restricted Cash [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 1,000	$ 1,000