Nature of Operations and Summary of Significant Accounting Policies - Company's Assets Measured at Fair Value (Detail) - USD ($)	Sep. 30, 2019	Sep. 30, 2018
Investment Holdings [Line Items]
Total	$ 105,322,000	$ 104,058,000	[1]
Level 1 [Member]
Investment Holdings [Line Items]
Total	66,632,000	74,174,000
Level 2 [Member]
Investment Holdings [Line Items]
Total	38,690,000	29,884,000
Equities [Member]
Investment Holdings [Line Items]
Total	10,412,000	11,768,000
Equities [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	10,412,000	11,768,000
Mutual Funds [Member]
Investment Holdings [Line Items]
Total	3,987,000	3,811,000
Mutual Funds [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	3,987,000	3,811,000
Exchange Traded Funds [Member]
Investment Holdings [Line Items]
Total	5,163,000	4,148,000
Exchange Traded Funds [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	5,163,000	4,148,000
Corporate Bonds [Member]
Investment Holdings [Line Items]
Total	38,690,000	29,884,000
Corporate Bonds [Member] | Level 2 [Member]
Investment Holdings [Line Items]
Total	38,690,000	29,884,000
Government Securities [Member]
Investment Holdings [Line Items]
Total	45,171,000	53,883,000
Government Securities [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	45,171,000	53,883,000
Cash and Money Funds [Member]
Investment Holdings [Line Items]
Total	1,899,000	564,000
Cash and Money Funds [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	$ 1,899,000	$ 564,000

[1] The amounts as of September 30, 2018 have been adjusted to reflect the change in inventory accounting method, as described in Notes 1 and 2 to the Consolidated Financial Statements.