Subsequent Events - Additional Information (Details) - USD ($)		3 Months Ended
	Jul. 13, 2020	Jun. 30, 2020
Subsequent Event [Line Items]
Common stock share value		$ 326,246,000
Gilead Collaboration Agreement | Gilead | Subsequent Event
Subsequent Event [Line Items]
Upfront cash payment	$ 175,000,000
Collaboration term for current and future clinical programs	10 years
Additional collaboration term for programs entering clinical development prior to end of collaboration term	3 years
Option fee per program for all other programs entering clinical development to exercise option	$ 150,000,000
Potential U.S. regulatory approval milestones receivable	500,000,000
Ongoing research and development support	400,000,000
Gilead Collaboration Agreement | Gilead | Subsequent Event | Minimum
Subsequent Event [Line Items]
Option fee per program for current clinical programs to exercise option	200,000,000
Gilead Collaboration Agreement | Gilead | Subsequent Event | Maximum
Subsequent Event [Line Items]
Option fee per program for current clinical programs to exercise option	275,000,000
Purchase Agreement | Gilead | Subsequent Event
Subsequent Event [Line Items]
Common stock share value	$ 200,000,000
Common stock shares issued	5,963,029
Shares issued, price per share	$ 33.54
Equity Agreements | Gilead | Subsequent Event
Subsequent Event [Line Items]
Percentage of option to purchase maximum shares of common stock	35.00%
Period over common stock to be purchased	5 years
Percentage of premium purchase price of common stock	20.00%
Trailing days average closing price	5 days
Initial purchase price	$ 33.54