Nature of Business - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Sep. 22, 2015	Dec. 31, 2015	Dec. 31, 2016
Class of Stock [Line Items]
Accumulated deficit		$ (51,620)	$ (114,587)
Cash, cash equivalents and marketable securities			$ 159,000
Common Stock [Member]
Class of Stock [Line Items]
Issuance of convertible preferred stock, shares		7,245,000
Conversion of convertible preferred stock into common stock upon initial public offering, Shares	16,298,045	16,298,000
Initial Public Offering [Member]
Class of Stock [Line Items]
Issuance of convertible preferred stock, shares	7,245,000
Stock issuance price per share	$ 22.00
Initial Public Offering [Member] | Common Stock [Member]
Class of Stock [Line Items]
Net proceeds from issuance of common stock	$ 145,200
Overallotment Option [Member]
Class of Stock [Line Items]
Issuance of convertible preferred stock, shares	945,000