Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Second Stock Purchase Agreement Gilead	Equity Award Programs	Common Stock	Common Stock Second Stock Purchase Agreement Gilead	Common Stock Equity Award Programs	Common Stock and Additional Paid-In Capital	Common Stock and Additional Paid-In Capital Second Stock Purchase Agreement Gilead	Common Stock and Additional Paid-In Capital Equity Award Programs	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2021	$ 842						$ 1,118			$ (275)	$ (1)
Balance, shares at Dec. 31, 2021				70.8
Issuance of common stock			$ 10						$ 10
Issuance of common stock, shares						0.8
Stock-based compensation	17						17
Other comprehensive gain (loss)	(4)										(4)
Net loss	(68)									(68)
Balance at Mar. 31, 2022	797						1,145			(343)	(5)
Balance, shares at Mar. 31, 2022				71.6
Balance at Dec. 31, 2021	842						1,118			(275)	(1)
Balance, shares at Dec. 31, 2021				70.8
Net loss	(135)
Balance at Jun. 30, 2022	747						1,164			(410)	(7)
Balance, shares at Jun. 30, 2022				72.1
Balance at Mar. 31, 2022	797						1,145			(343)	(5)
Balance, shares at Mar. 31, 2022				71.6
Issuance of common stock			4						4
Issuance of common stock, shares						0.5
Stock-based compensation	15						15
Other comprehensive gain (loss)	(2)										(2)
Net loss	(67)									(67)
Balance at Jun. 30, 2022	747						1,164			(410)	(7)
Balance, shares at Jun. 30, 2022				72.1
Balance at Dec. 31, 2022	$ 657						1,206			(542)	(7)
Balance, shares at Dec. 31, 2022	72.9			72.9
Issuance of common stock			1						1
Issuance of common stock, shares						0.2
Stock-based compensation	$ 19						19
Other comprehensive gain (loss)	3										3
Net loss	(80)									(80)
Balance at Mar. 31, 2023	600						1,226			(622)	(4)
Balance, shares at Mar. 31, 2023				73.1
Balance at Dec. 31, 2022	$ 657						1,206			(542)	(7)
Balance, shares at Dec. 31, 2022	72.9			72.9
Net loss	$ (155)
Balance at Jun. 30, 2023	$ 566						1,267			(697)	(4)
Balance, shares at Jun. 30, 2023	74.5			74.5
Balance at Mar. 31, 2023	$ 600						1,226			(622)	(4)
Balance, shares at Mar. 31, 2023				73.1
Issuance of common stock		$ 20	$ 3					$ 20	$ 3
Issuance of common stock, shares					1.0	0.4
Stock-based compensation	18						18
Net loss	(75)									(75)
Balance at Jun. 30, 2023	$ 566						$ 1,267			$ (697)	$ (4)
Balance, shares at Jun. 30, 2023	74.5			74.5