CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (8,395)	$ (15,361)	$ (20,679)	$ (32,818)
Other comprehensive loss
Unrealized losses on available-for-sale investments, net of taxes	(518)	(139)	(2,004)	(357)
Comprehensive loss	(8,913)	(15,500)	(22,683)	(33,175)
Comprehensive loss attributable to noncontrolling interest	(6)		(6)
Total comprehensive loss attributable to Cerus Corporation	$ (8,907)	$ (15,500)	$ (22,677)	$ (33,175)