Cash equivalents and marketable securities (Details)	Jun. 30, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 8,001,815	$ 38,660,547
Unrealized Gains	0	2,912
Unrealized Losses	(5,616)	(4,526)
Fair Value	$ 7,996,199	$ 38,658,933
Number of debt securities held \| security	3	6
Aggregate fair value of debt securities in an unrealized loss position	$ 7,996,199	$ 16,519,620
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,001,815	31,060,710
Unrealized Gains	0	2,912
Unrealized Losses	(5,616)	(4,131)
Fair Value	$ 7,996,199	31,059,491
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		6,081,202
Unrealized Gains		0
Unrealized Losses		0
Fair Value		6,081,202
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		1,518,635
Unrealized Gains		0
Unrealized Losses		(395)
Fair Value		$ 1,518,240

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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