Summary of Significant Accounting Policies - Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021
Accounting Policies [Abstract]
Oil, natural gas and NGL sales	$ 17,562	$ 17,008
Joint interest accounts receivable	409	413
Realized derivative receivable	0	42
Other accounts receivable	31	10
Total accounts receivable	$ 18,002	$ 17,473