Summary of Significant Accounting Policies - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Accounting Policies [Abstract]
Accrued capital expenditures	$ 12,215	$ 2,964
Accrued lease operating expenses	2,249	1,617
Accrued ad valorem tax	365	680
Accrued general and administrative costs	2,151	2,125
Accrued interest expense	28	63
Accrued dividends on preferred units	0	903
Accrued dividends on common units	0	95
Accrued dividends on common shares	4,991	0
Accrued stock-based compensation liability	4,162	0
Other accrued expenditures	338	299
Total accrued liabilities	$ 26,499	$ 8,746