Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional paid in capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Balances at Dec. 31, 2019	$ 450,197	$ 4	$ 627,810	$ 205	$ (177,822)
Balances (Shares) at Dec. 31, 2019		36,992
Exercise of stock options	2,154		2,154
Exercise of stock options, Shares		181
Issuance of common stock under employee stock purchase plan	607		607
Issuance of common stock under employee stock purchase plan, shares		17
Stock-based compensation expense	8,017		8,017
Unrealized loss on available-for-sale securities, net	(785)			(785)
Net loss	(40,038)				(40,038)
Balances at Mar. 31, 2020	420,152	$ 4	638,588	(580)	(217,860)
Balances (Shares) at Mar. 31, 2020		37,190
Balances at Dec. 31, 2020	377,753	$ 4	667,181	(360)	(289,072)
Balances (Shares) at Dec. 31, 2020		37,476
Issuance of common stock upon public offering, net of transaction costs	216,059		216,059
Issuance of stock, net of transaction costs		4,899
Exercise of stock options	1,292		1,292
Exercise of stock options, Shares		111
Issuance of common stock under employee stock purchase plan	627		627
Issuance of common stock under employee stock purchase plan, shares		19
Stock-based compensation expense	9,920		9,920
Unrealized loss on available-for-sale securities, net	(1,008)			(1,008)
Net loss	(50,139)				(50,139)
Balances at Mar. 31, 2021	$ 554,504	$ 4	$ 895,079	$ (1,368)	$ (339,211)
Balances (Shares) at Mar. 31, 2021		42,505