Marketable Securities - Company's Marketable Securities Measured at Fair Value (Detail) - USD ($)	Jun. 30, 2017	Sep. 30, 2016
Investment Holdings [Line Items]
Total	$ 87,132,000	$ 85,938,000
Equities [Member]
Investment Holdings [Line Items]
Total	11,037,000	2,408,000
Mutual Funds [Member]
Investment Holdings [Line Items]
Total	6,013,000	5,212,000
Exchange Traded Funds [Member]
Investment Holdings [Line Items]
Total	1,440,000	510,000
Government Securities [Member]
Investment Holdings [Line Items]
Total	66,090,000	69,583,000
Cash and Money Funds [Member]
Investment Holdings [Line Items]
Total	2,552,000	8,225,000
Level 1 [Member]
Investment Holdings [Line Items]
Total	87,132,000	85,938,000
Level 1 [Member] | Equities [Member]
Investment Holdings [Line Items]
Total	11,037,000	2,408,000
Level 1 [Member] | Mutual Funds [Member]
Investment Holdings [Line Items]
Total	6,013,000	5,212,000
Level 1 [Member] | Exchange Traded Funds [Member]
Investment Holdings [Line Items]
Total	1,440,000	510,000
Level 1 [Member] | Government Securities [Member]
Investment Holdings [Line Items]
Total	66,090,000	69,583,000
Level 1 [Member] | Cash and Money Funds [Member]
Investment Holdings [Line Items]
Total	$ 2,552,000	$ 8,225,000