Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 77	$ 67	$ 175	$ 124
Cerus Europe B.V.
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 100	$ 100	$ 200	$ 100