Retirement and Other Benefit Plans (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2020 USD ($)
Retirement and Other Benefit Plans
Employer contributions	$ 25,700
Plan liabilities settled	32,400
Plan liabilities settled by entering into an agreement to purchase annuities from Massachusetts Mutual Life Insurance Company	69,100
Charges associated with these settlements	$ 40,600