Summary of Significant Accounting Policies - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Mar. 10, 2021	Feb. 26, 2021	Sep. 30, 2020
Business Acquisition [Line Items]
Allowance for doubtful accounts	$ 0		$ 0				$ 0
Transaction costs	2,164,000	$ 28,000	3,213,000	$ 27,000
Unrecognized tax benefits	0		0				$ 0
Kansas Properties
Business Acquisition [Line Items]
Goodwill	19,100,000		19,100,000
Discontinued operation, carrying value	22,000,000.0		22,000,000.0
Discontinued operation, fair value	3,500,000		3,500,000
Goodwill, impairment loss			18,500,000
Kansas Properties
Business Acquisition [Line Items]
Consideration					$ 3,500,000
Kansas Properties | Valuation Technique, Discounted Cash Flow
Business Acquisition [Line Items]
Discontinued operation, fair value	4,600,000		4,600,000
Riley Exploration
Business Acquisition [Line Items]
Goodwill						$ 19,057,000
Transaction costs			4,500,000
Riley Exploration | General and Administrative Expense
Business Acquisition [Line Items]
Transaction costs	$ 2,200,000		$ 3,100,000