Nature of Organization and Operations - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended
	Jul. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Nature Of Organization And Operations [Line Items]
Cash and cash equivalents and available for sale securities		$ 321,215	$ 260,343
Number of months for operating plan sufficiently funded by cash resources		12 months
Follow-on public offering | Subsequent Event
Nature Of Organization And Operations [Line Items]
Proceeds from issuance of initial public offering	$ 62,600