Stockholders' Equity - Schedule of Changes in Stockholders Equity (Detail) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Class Of Stock [Line Items]
Beginning balance	$ 880,547	$ 953,754	$ 1,040,244	$ 494,813	$ 545,873	$ 527,072	$ 1,040,244	$ 527,072
Beginning balance, shares			74,485,883				74,485,883
Exercise of stock options	722	4,827	$ 8,435	20,365	6,163	13,340
Exercise of stock options, shares							852,913
Issuance of shares under employee stock purchase plan		1,068			970
Equity-based compensation	25,215	23,068	18,491	15,410	10,614	6,424
Other comprehensive loss				(161)
Other comprehensive loss - unrealized loss on marketable securities	991	(932)	(5,128)		(1)	(13)
Other comprehensive loss from equity method investment	(805)	(560)	(302)	0			$ (1,667)	0
Net loss	(113,229)	(100,678)	(146,872)	(71,644)	(68,806)	(46,205)	(360,779)	(186,655)
Ending balance	$ 824,951	880,547	953,754	1,107,098	494,813	545,873	$ 824,951	1,107,098
Ending balance, shares	76,587,947						76,587,947
Follow-on Offering [Member]
Class Of Stock [Line Items]
Issuance of common stock				648,315
At The Market Offerings [Member]
Class Of Stock [Line Items]
Issuance of common stock	$ 31,510		38,886			45,255
Common Stock [Member]
Class Of Stock [Line Items]
Beginning balance	$ 8	$ 8	$ 7	$ 7	$ 7	$ 7	$ 7	$ 7
Beginning balance, shares	76,000,745	75,624,167	74,485,883	68,331,780	67,890,334	66,234,056	74,485,883	66,234,056
Exercise of stock options, shares	33,336	315,747	503,830	1,227,067	394,801	1,014,569
Vesting of restricted stock units, shares	662	36,515	54,666	24,711	26,235
Issuance of shares under employee stock purchase plan, shares		24,316			20,410
Ending balance	$ 8	$ 8	$ 8	$ 7	$ 7	$ 7	$ 8	$ 7
Ending balance, shares	76,587,947	76,000,745	75,624,167	74,342,178	68,331,780	67,890,334	76,587,947	74,342,178
Common Stock [Member] | Follow-on Offering [Member]
Class Of Stock [Line Items]
Number of stock additionally invested				4,758,620
Common Stock [Member] | At The Market Offerings [Member]
Class Of Stock [Line Items]
Issuance of common stock			$ 1
Number of stock additionally invested	553,204		579,788			641,709
Additional Paid-In Capital [Member]
Class Of Stock [Line Items]
Beginning balance	$ 1,840,644	$ 1,811,681	$ 1,745,870	$ 1,044,939	$ 1,027,192	$ 962,173	$ 1,745,870	$ 962,173
Exercise of stock options	722	4,827	8,435	20,365	6,163	13,340
Issuance of shares under employee stock purchase plan		1,068			970
Equity-based compensation	25,215	23,068	18,491	15,410	10,614	6,424
Ending balance	1,898,091	1,840,644	1,811,681	1,729,029	1,044,939	1,027,192	1,898,091	1,729,029
Additional Paid-In Capital [Member] | Follow-on Offering [Member]
Class Of Stock [Line Items]
Issuance of common stock				648,315
Additional Paid-In Capital [Member] | At The Market Offerings [Member]
Class Of Stock [Line Items]
Issuance of common stock	31,510		38,885			45,255
Accumulated Other Comprehensive Loss [Member]
Class Of Stock [Line Items]
Beginning balance	(9,554)	(8,062)	(2,632)	(13)	(12)	1	(2,632)	1
Other comprehensive loss				(161)
Other comprehensive loss - unrealized loss on marketable securities	991	(932)	(5,128)		(1)	(13)
Other comprehensive loss from equity method investment	(805)	(560)	(302)
Ending balance	(9,368)	(9,554)	(8,062)	(174)	(13)	(12)	(9,368)	(174)
Accumulated Deficit [Member]
Class Of Stock [Line Items]
Beginning balance	(950,551)	(849,873)	(703,001)	(550,120)	(481,314)	(435,109)	(703,001)	(435,109)
Net loss	(113,229)	(100,678)	(146,872)	(71,644)	(68,806)	(46,205)
Ending balance	$ (1,063,780)	$ (950,551)	$ (849,873)	$ (621,764)	$ (550,120)	$ (481,314)	$ (1,063,780)	$ (621,764)