Organization and Nature of Business - IPO, Stock Split, Liquidity (Details) $ / shares in Units, $ in Thousands					12 Months Ended
	Nov. 17, 2016 USD ($) $ / shares shares	Jun. 02, 2016 USD ($) $ / shares shares	Oct. 13, 2015 USD ($) $ / shares shares	Sep. 24, 2015	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Initial public offering
Number of shares issued | shares	4,000,000
Issuance price (in dollars per share) | $ / shares	$ 22.75
Gross proceeds	$ 91,000
Issuance of stock upon conversion, shares | shares			11,677,076
Offering costs	188
Offering proceeds, net of discounts, commissions and expenses	$ 98,158
Proceeds from initial public offering, net of offering costs						$ 56,550
Proceeds from issuance of common stock in connection with private placement, net of issuance costs					$ 18,547
Reverse stock split				0.2899
Cash, cash equivalents and marketable securities					174,134
Proceeds from sale of stock, net of issuance costs					$ 98,158
IPO
Initial public offering
Number of shares issued | shares			5,000,000
Issuance price (in dollars per share) | $ / shares			$ 11.00
Gross proceeds			$ 55,000
Offering costs			2,272
Proceeds from initial public offering, net of offering costs			$ 56,550
Exercise of over-allotment option
Initial public offering
Number of shares issued | shares	600,000		750,000
Issuance price (in dollars per share) | $ / shares	$ 22.75		$ 11.00
Gross proceeds	$ 13,650		$ 8,250
Offering costs	$ 6,279		$ 4,428
Private Placement [Member]
Initial public offering
Number of shares issued | shares		1,081,082
Issuance price (in dollars per share) | $ / shares		$ 18.50
Gross proceeds		$ 20,000
Offering costs		153
Placement fees		1,300
Proceeds from issuance of common stock in connection with private placement, net of issuance costs		$ 18,547