Reconciliation of Numerator and Denominator Used in Computation of Basic and Diluted Net Income Loss per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Numerator for Basic and Diluted:
Net loss attributable to Cerus Corporation	$ (42,779)	$ (54,374)	$ (59,857)
Denominator:
Basic weighted average number of shares outstanding	176,545	171,279	163,949
Diluted weighted average number of shares outstanding	176,545	171,279	163,949
Net loss per share attributable to Cerus Corporation
Basic	$ (0.24)	$ (0.32)	$ (0.37)
Diluted	$ (0.24)	$ (0.32)	$ (0.37)