Nature of Operations and Summary of Significant Accounting Policies - Company's Assets Measured at Fair Value (Detail) - USD ($)	Sep. 30, 2021	Sep. 30, 2020
Investment Holdings [Line Items]
Total	$ 94,976,000	$ 89,498,000
Level 1 [Member]
Investment Holdings [Line Items]
Total	70,123,000	61,621,000
Level 2 [Member]
Investment Holdings [Line Items]
Total	24,853,000	27,877,000
Equities [Member]
Investment Holdings [Line Items]
Total	14,734,000	11,949,000
Equities [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	14,734,000	11,949,000
Mutual Funds [Member]
Investment Holdings [Line Items]
Total	10,357,000	9,595,000
Mutual Funds [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	10,357,000	9,595,000
Exchange Traded Funds [Member]
Investment Holdings [Line Items]
Total	9,458,000	10,344,000
Exchange Traded Funds [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	9,458,000	10,344,000
Corporate Bonds [Member]
Investment Holdings [Line Items]
Total	24,853,000	27,877,000
Corporate Bonds [Member] | Level 2 [Member]
Investment Holdings [Line Items]
Total	24,853,000	27,877,000
Government Securities [Member]
Investment Holdings [Line Items]
Total	30,999,000	16,147,000
Government Securities [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	30,999,000	16,147,000
Cash and Money Funds [Member]
Investment Holdings [Line Items]
Total	4,575,000	13,586,000
Cash and Money Funds [Member] | Level 1 [Member]
Investment Holdings [Line Items]
Total	$ 4,575,000	$ 13,586,000