Agreements - Gilead (Details) $ / shares in Units, $ in Thousands		2 Months Ended	3 Months Ended	12 Months Ended
	Dec. 19, 2018 USD ($) item $ / shares shares	Jul. 31, 2019 $ / shares shares	Jun. 30, 2018 $ / shares shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Agreements
Accounts receivable				$ 25,000
Sale of common shares (in shares) | shares		3,450,000	6,164,000
Purchase price (in dollars per share) | $ / shares		$ 15.00	$ 14.00
Sale of common shares				48,348	$ 17,096
Revenue earned				20,492
Gilead
Agreements
Number of programs | item	3
Option exercise period	90 days
Revenue proceeds	$ 50,000
Potential milestone payments	$ 475,000
Accounts receivable				25,000
Refundable payments under the agreement				0
Sale of common shares (in shares) | shares	980,392
Purchase price (in dollars per share) | $ / shares	$ 30.60
Sale of common shares	$ 30,000
Maximum number of program antibodies to be notified which satisfies development criteria | item	2
Transaction price	$ 80,000
Research collaboration term	3 years
Equity investment included in transaction price	$ 17,100
Contract liability	62,900			67,400
Securities premium				12,900
Revenue earned				20,500
Deferred revenue recognized				$ 14,700
Gilead | Maximum
Agreements
Potential milestone payments	$ 1,425,000