Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 61	$ 59	$ 121	$ 113
Cerus Europe B.V.
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 100	$ 100	$ 100	$ 100