Nature of Operations and Summary of Significant Accounting Policies - Company's Assets Measured at Fair Value (Detail) - USD ($)	Sep. 30, 2022	Sep. 30, 2021
Investment Holdings [Line Items]
Total	$ 89,300,000	$ 94,976,000
Level 1 [Member]
Investment Holdings [Line Items]
Total	51,961,000	70,123,000
Level 2 [Member]
Investment Holdings [Line Items]
Total	37,339,000	24,853,000
Equities [Member]
Investment Holdings [Line Items]
Total	12,149,000	14,734,000
Equities [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	12,149,000	14,734,000
Mutual Funds [Member]
Investment Holdings [Line Items]
Total	5,337,000	10,357,000
Mutual Funds [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	5,337,000	10,357,000
Exchange Traded Funds [Member]
Investment Holdings [Line Items]
Total	4,794,000	9,458,000
Exchange Traded Funds [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	4,794,000	9,458,000
Corporate Bonds [Member]
Investment Holdings [Line Items]
Total	37,339,000	24,853,000
Corporate Bonds [Member] | Level 2 [Member]
Investment Holdings [Line Items]
Total	37,339,000	24,853,000
Government Securities [Member]
Investment Holdings [Line Items]
Total	29,327,000	30,999,000
Government Securities [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	29,327,000	30,999,000
Cash and Money Funds [Member]
Investment Holdings [Line Items]
Total	354,000	4,575,000
Cash and Money Funds [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	$ 354,000	$ 4,575,000