Organization - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Date of incorporation		Jun. 08, 2012
Accumulated deficit	$ 240,023	$ 240,023	$ 202,553
Proceeds from offering, net of underwriting discounts and commissions and offering expenses		271,520
Cash, cash equivalents and short and long-term investments	$ 628,300	$ 628,300
Follow-On-Offering
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Common stock shares issued	5,663,750
Common stock shares issued, price per share	$ 51.00	$ 51.00
Proceeds from offering, net of underwriting discounts and commissions and offering expenses		$ 271,200
Over Allotment Option
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Common stock shares issued	738,750