Summary of Significant Accounting Policies (Reconciliation of Basic and Diluted Earnings Per Share) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net income	$ (329,296)	$ 1,206,578	$ 5,680,316	$ 4,006,936	$ 455,605	$ 1,138,555	$ 4,670,090	$ 2,434,162	$ 10,564,534	$ 8,698,412
Weighted-average common shares (in shares)									8,125,938	8,039,484
Effect of dilutive securities:
Options to purchase common stock (in shares)									20,728	39,466
Diluted average common shares (in shares)									8,146,666	8,078,950
Earnings Per Share of Common Stock:
Basic (in usd per share)	$ (0.04)	$ 0.15	$ 0.70	$ 0.50	$ 0.06	$ 0.14	$ 0.58	$ 0.30	$ 1.30	$ 1.08
Diluted (in usd per share)	$ (0.04)	$ 0.15	$ 0.70	$ 0.49	$ 0.06	$ 0.14	$ 0.58	$ 0.30	$ 1.30	$ 1.08