Fair Value Measurements and Disclosures about Fair Value of Financial Instruments - Reconciliation of derivative Assets measured on a Recurring Basis, Unobservable Input (Level 3) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Fair Value Measurements and Disclosures about Fair Value of Financial Instruments
Beginning balance	$ 11,415,000	$ 2,921,000	$ 14,937,000	$ 3,269,000
Unrealized gains/(losses) recognized in earnings, net of settlements	(11,153,000)	2,757,000	(14,675,000)	2,409,000
Ending balance	$ 262,000	$ 5,678,000	$ 262,000	$ 5,678,000