Retirement and Other Benefit Plans - Additional information (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Retirement and Other Benefit Plans
Defined Benefit Plan Before Adoption Of Sfas 158 Recognition Provision Accrued Benefit Liability	$ 200	$ 200	$ 600
Plan liabilities settled	32,400
Charges associated with these settlements	40,600	40,600
Plan liabilities settled by entering into an agreement to purchase annuities from Massachusetts Mutual Life Insurance Company		69,100
Cash contributed to the plan	$ 25,700	$ 26,400	$ 2,700