Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Payables and Accruals [Abstract]
Accrued compensation	$ 47,360	$ 46,465
Income taxes payable	16,836	16,216
Dividends payable	13,827	13,669
ARO (current)	11,933	0
Contract liabilities (current)	8,883	8,501
Current portion of operating lease liability	7,646	6,513
Taxes, other than income taxes	6,620	5,044
Current portion of terminated swap liability (See Note 15)	5,855	0
Goods and services received, not yet invoiced	3,866	3,957
Interest rate swap liability	2,995	11,992
Accrued interest	1,846	29
Other	12,130	9,056
Total	$ 139,797	$ 121,442