Cash equivalents and marketable securities (Tables)

12 Months Ended

Dec. 31, 2016

Cash and Cash Equivalents [Abstract]

Schedule of Marketable Securities

Marketable securities at December 31, 2016 and December 31, 2015 consisted of the following:

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
As of December 31, 2016
Current (due within 1 year):
Corporate debt securities	$	1,518,635	$	—	$	(395	)	$	1,518,240
Commercial paper	6,081,202		—		—			6,081,202
U.S. government agency securities	31,060,710		2,912		(4,131		)	31,059,491
Total	$	38,660,547	$	2,912	$	(4,526	)	$	38,658,933

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
As of December 31, 2015
Current (due within 1 year):
Corporate debt securities	$	24,666,607	$	1,878	$	(16,137	)	$	24,652,348
Noncurrent (due after 1 year through 5 years):
Corporate debt securities	2,323,344				(10,395		)	2,312,949
Total	$	26,989,951	$	1,878	$	(26,532	)	$	26,965,297