Stockholders' Equity - Schedule of Changes in Stockholders Equity (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Class Of Stock [Line Items]
Beginning balance	$ 527,072	$ 269,881
Beginning balance, shares	66,234,056
Exercise of stock options	$ 13,340	336
Exercise of stock options, shares	1,014,569
Equity-based compensation	$ 6,424	4,157
Other comprehensive income (loss)	(13)	112
Net loss	(46,205)	(31,806)
Ending balance	$ 545,873	247,759
Ending balance, shares	67,890,334
At The Market Offerings [Member]
Class Of Stock [Line Items]
Issuance of common stock	$ 45,255	5,079
Common Stock [Member]
Class Of Stock [Line Items]
Beginning balance	$ 7	$ 5
Beginning balance, shares	66,234,056	50,198,044
Exercise of stock options, shares	1,014,569	53,579
Ending balance	$ 7	$ 5
Ending balance, shares	67,890,334	50,602,875
Common Stock [Member] | At The Market Offerings [Member]
Class Of Stock [Line Items]
Issuance of common stock, shares	641,709	351,252
Additional Paid-In Capital [Member]
Class Of Stock [Line Items]
Beginning balance	$ 962,173	$ 570,493
Exercise of stock options	13,340	336
Equity-based compensation	6,424	4,157
Ending balance	1,027,192	580,065
Additional Paid-In Capital [Member] | At The Market Offerings [Member]
Class Of Stock [Line Items]
Issuance of common stock	45,255	5,079
Accumulated Other Comprehensive Income (Loss) [Member]
Class Of Stock [Line Items]
Beginning balance	1	261
Other comprehensive income (loss)	(13)	112
Ending balance	(12)	373
Accumulated Deficit [Member]
Class Of Stock [Line Items]
Beginning balance	(435,109)	(300,878)
Net loss	(46,205)	(31,806)
Ending balance	$ (481,314)	$ (332,684)