Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($)	Mar. 31, 2020	Sep. 30, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Netting and Cash Collateral	$ 0	$ 0
Financial instruments net assets	882,000	1,811,000
Debt and equity securities	96,079,000	101,883,000
Total assets	96,961,000	103,694,000
Netting and Cash Collateral	0	0
Financial instruments net liability	1,714,000	5,801,000
Registered investment companies
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	35,839,000	41,406,000
Bond mutual funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	25,905,000	25,966,000
Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities	32,520,000	31,915,000
Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	1,815,000	2,596,000
Fair Value Inputs Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial instruments gross assets	0	0
Debt and equity securities	61,744,000	67,372,000
Total assets	61,744,000	67,372,000
Financial instruments gross liability	0	0
Fair Value Inputs Level 1 | Registered investment companies
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	35,839,000	41,406,000
Fair Value Inputs Level 1 | Bond mutual funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	25,905,000	25,966,000
Fair Value Inputs Level 1 | Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities	0	0
Fair Value Inputs Level 1 | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	0	0
Fair Value Inputs Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial instruments gross assets	882,000	1,811,000
Debt and equity securities	34,335,000	34,511,000
Total assets	35,217,000	36,322,000
Financial instruments gross liability	1,714,000	5,801,000
Fair Value Inputs Level 2 | Registered investment companies
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	0	0
Fair Value Inputs Level 2 | Bond mutual funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	0	0
Fair Value Inputs Level 2 | Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities	32,520,000	31,915,000
Fair Value Inputs Level 2 | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	1,815,000	2,596,000
Fair Value Inputs Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial instruments gross assets	0	0
Debt and equity securities	0	0
Total assets	0	0
Financial instruments gross liability	0	0
Fair Value Inputs Level 3 | Registered investment companies
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	0	0
Fair Value Inputs Level 3 | Bond mutual funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	0	0
Fair Value Inputs Level 3 | Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities	0	0
Fair Value Inputs Level 3 | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	$ 0	$ 0