Marketable Securities - Company's Assets Measured at Fair Value (Detail) - USD ($)	Dec. 31, 2015	Sep. 30, 2015
Investment Holdings [Line Items]
Total	$ 85,335,000	$ 84,357,000
Equities [Member]
Investment Holdings [Line Items]
Total	21,938,000	20,915,000
Mutual Funds [Member]
Investment Holdings [Line Items]
Total	8,312,000	11,885,000
Exchange Traded Funds [Member]
Investment Holdings [Line Items]
Total	6,793,000	4,086,000
Government Securities [Member]
Investment Holdings [Line Items]
Total	45,868,000	43,883,000
Cash and Money Funds [Member]
Investment Holdings [Line Items]
Total	2,424,000	3,588,000
Level 1 [Member]
Investment Holdings [Line Items]
Total	85,335,000	84,357,000
Level 1 [Member] | Equities [Member]
Investment Holdings [Line Items]
Total	21,938,000	20,915,000
Level 1 [Member] | Mutual Funds [Member]
Investment Holdings [Line Items]
Total	8,312,000	11,885,000
Level 1 [Member] | Exchange Traded Funds [Member]
Investment Holdings [Line Items]
Total	6,793,000	4,086,000
Level 1 [Member] | Government Securities [Member]
Investment Holdings [Line Items]
Total	45,868,000	43,883,000
Level 1 [Member] | Cash and Money Funds [Member]
Investment Holdings [Line Items]
Total	$ 2,424,000	$ 3,588,000