Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 60	$ 54
Cerus Europe B.V. | Maximum
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 100	$ 100