Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 56	$ 50	$ 169	$ 3,961
Cerus Europe B.V.
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 100	$ 100	$ 200
Aduro
Income Tax Disclosure [Line Items]
Income tax expense (benefit)				$ 4,000