Fair Value Measurements - Schedule of Assets Measured at Fair Value on Recurring Basis (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	$ 160,547,550	$ 78,083,604
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	94,397,188	44,181,756
Total short-term investments	160,547,550	78,083,604
Total financial assets	254,944,738	122,265,360
Fair Value, Measurements, Recurring | Money Market Mutual Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	35,781,822	44,181,756
Fair Value, Measurements, Recurring | Asset-backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	20,159,772	7,421,703
Fair Value, Measurements, Recurring | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	32,876,471
Total short-term investments	53,019,143	34,882,298
Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	5,643,984
Total short-term investments	58,467,890	26,856,283
Fair Value, Measurements, Recurring | U.S Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	20,094,911
Total short-term investments	28,900,745	8,923,320
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	35,781,822	44,181,756
Total financial assets	35,781,822	44,181,756
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Money Market Mutual Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	35,781,822	44,181,756
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	58,615,366
Total short-term investments	160,547,550	78,083,604
Total financial assets	219,162,916	78,083,604
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Asset-backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	20,159,772	7,421,703
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	32,876,471
Total short-term investments	53,019,143	34,882,298
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	5,643,984
Total short-term investments	58,467,890	26,856,283
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	20,094,911
Total short-term investments	$ 28,900,745	$ 8,923,320