Development and License Agreements - Additional Information (Detail) € in Millions	1 Months Ended	3 Months Ended		9 Months Ended			12 Months Ended
	Aug. 31, 2019 EUR (€)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2019 EUR (€)	Sep. 30, 2018 USD ($)	Dec. 31, 2016 EUR (€)	Dec. 31, 2018 USD ($)
Licenses Agreements [Line Items]
Payments made relating to the manufacturing of the products		$ 9,800,000	$ 5,600,000	$ 23,300,000		$ 15,700,000
BARDA Agreement
Licenses Agreements [Line Items]
Committed fund receivable		103,200,000		103,200,000
Committed fund receivable		201,200,000		$ 201,200,000
Period of agreement				5 years	5 years
Accounts receivable of billed and unbilled amounts		$ 4,100,000		$ 4,100,000				$ 2,300,000
Cerus Corporation \| BARDA Agreement
Licenses Agreements [Line Items]
Co-investment by the company				5,000,000.0
Additional co-investment by the company				$ 9,600,000
Manufacturing and Supply Agreement \| Fresenius
Licenses Agreements [Line Items]
Payments made based on the successful achievement of production volumes \| €					€ 8.6
Manufacturing and development payments \| €	€ 5.5						€ 3.1
Manufacturing and Supply Agreement \| Fresenius \| Measurement Input, Discount Rate
Licenses Agreements [Line Items]
Manufacturing and development obligations, discount rate							9.72