Fair value measurements (Tables)

6 Months Ended

Jun. 30, 2016

Fair Value Disclosures [Abstract]

Summary of Cash Equivalents and Marketable Securities Measured at Fair Value on a Recurring Basis

The following tables summarize the cash equivalents and marketable securities measured at fair value on a recurring basis as of June 30, 2016 and December 31, 2015:

	Level 1		Level 2		Level 3		Balance as of June 30, 2016
Cash equivalents	$	34,259,641	$	—	$	—	$	34,259,641
Marketable securities:
Corporate debt securities	—		13,812,453		—		13,812,453
U.S. government agency securities	—		22,100,327		—		22,100,327
	$	34,259,641	$	35,912,780	$	—	$	70,172,421

	Level 1		Level 2		Level 3		Balance as of December 31, 2015
Cash equivalents	$	58,575,348	$	1,410,322	$	—	$	59,985,670
Marketable securities:
Corporate debt securities	—		26,965,297		—		26,965,297
	$	58,575,348	$	28,375,619	$	—	$	86,950,967