Marketable Securities - Company's Assets Measured at Fair Value (Detail) (USD $)	Dec. 31, 2014	Sep. 30, 2014
Investment Holdings [Line Items]
Total	$ 87,008,000	$ 87,112,000
Equities [Member]
Investment Holdings [Line Items]
Total	17,963,000	17,102,000
Mutual Funds [Member]
Investment Holdings [Line Items]
Total	11,658,000	19,088,000
Exchange-Traded Funds [Member]
Investment Holdings [Line Items]
Total	2,028,000	1,764,000
Government Securities [Member]
Investment Holdings [Line Items]
Total	44,032,000	43,999,000
Cash and Money Funds [Member]
Investment Holdings [Line Items]
Total	11,327,000	5,159,000
Level 1 [Member]
Investment Holdings [Line Items]
Total	87,008,000	87,112,000
Level 1 [Member] | Equities [Member]
Investment Holdings [Line Items]
Total	17,963,000	17,102,000
Level 1 [Member] | Mutual Funds [Member]
Investment Holdings [Line Items]
Total	11,658,000	19,088,000
Level 1 [Member] | Exchange-Traded Funds [Member]
Investment Holdings [Line Items]
Total	2,028,000	1,764,000
Level 1 [Member] | Government Securities [Member]
Investment Holdings [Line Items]
Total	44,032,000	43,999,000
Level 1 [Member] | Cash and Money Funds [Member]
Investment Holdings [Line Items]
Total	$ 11,327,000	$ 5,159,000