Investments - Summary of Short-term and Long-term Investments (Detail) - USD ($)	Sep. 30, 2019	Sep. 30, 2018
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	$ 81,075,887	$ 46,400,176
Gross Unrealized Gains	1,097,842
Gross Unrealized Losses		(429,050)
Fair Value	82,173,729	45,971,126
Commercial Notes Due Within One Year
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	36,899,894	46,400,176
Gross Unrealized Gains	222,584
Gross Unrealized Losses		(429,050)
Fair Value	37,122,478	$ 45,971,126
Commercial Notes Due Within Three Years
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	44,175,993
Gross Unrealized Gains	875,258
Fair Value	$ 45,051,251

Amount of investment in debt security measured at amortized cost (held-to-maturity).

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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-Name Accounting Standards Codification
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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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