Accrued Expenses, Income Taxes Payable And Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Payables and Accruals [Abstract]
Accrued compensation	$ 27,078	$ 46,465
Income taxes payable	15,909	16,216
Dividends payable	13,216	13,669
Contract liabilities (current)	8,150	8,501
Current portion of operating lease liability	6,602	6,513
Current portion of terminated swap liability (See Note 10)	5,855	0
Taxes, other than income taxes	5,517	5,044
Goods and services received, not yet invoiced	4,479	3,957
Interest rate swap liability (See Note 10)	2,869	11,992
Accrued interest	114	29
Other	9,085	9,056
Total	$ 98,874	$ 121,442