Segment Information (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2025 USD ($) segment	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment		1
Number of reportable segments | segment		1
Total collaboration revenue		$ 0	$ 0	$ 330,531
Expenses
Total research and development expenses	[1]	418,778	396,440	423,876
Total general and administrative expenses		136,564	105,438	103,354
Total operating expenses		555,342	501,878	527,230
Segment gain from divestiture of small molecule programs		0	14,537	0
Loss from operations		(555,342)	(487,341)	(196,699)
Segment interest and other income, net		42,904	64,636	51,505
Loss before income taxes		(512,438)	(422,705)	(145,194)
Therapeutics Segment
Segment Reporting Information [Line Items]
Total collaboration revenue		0	0	330,531
Expenses
Other research and development expenses		86,958	62,715	74,518
Personnel related research and development expenses		168,221	152,906	160,444
Total research and development expenses		418,778	396,440	423,876
Personnel related general and administrative expenses		86,234	73,505	73,668
Other general and administrative expenses		50,330	31,933	29,686
Total general and administrative expenses		136,564	105,438	103,354
Total operating expenses		555,342	501,878	527,230
Segment gain from divestiture of small molecule programs		0	14,537	0
Loss from operations		(555,342)	(487,341)	(196,699)
Segment interest and other income, net		42,904	64,636	51,505
Loss before income taxes		(512,438)	(422,705)	(145,194)
Therapeutics Segment | TV Programs, Including Cost Sharing
Expenses
External research and development expense		154,799	138,196	139,064
Therapeutics Segment | Small Molecule Programs, Including Cost Sharing
Expenses
External research and development expense		$ 8,800	$ 42,623	$ 49,850

[1] Includes expense for cost sharing payments to a related party of $17.7 million for the year ended December 31, 2023.