Development and License Agreements - Additional Information (Detail) € in Millions	1 Months Ended	3 Months Ended		6 Months Ended			12 Months Ended
	Aug. 31, 2018 EUR (€)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2019 EUR (€)	Jun. 30, 2018 USD ($)	Dec. 31, 2016 EUR (€)	Jun. 30, 2019 EUR (€)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 EUR (€)
Licenses Agreements [Line Items]
Payments made relating to the manufacturing of the products		$ 5,600,000	$ 4,800,000	$ 13,400,000		$ 10,200,000
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		4,200,000		$ 4,200,000					$ 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 | €							€ 3.1
Remaining amount payable for manufacturing and development | €	€ 5.5
Manufacturing and Supply Agreement | Fresenius | Manufacturing and Development Obligations - Current
Licenses Agreements [Line Items]
Accrual for manufacturing and development of entity products		$ 6,200,000		$ 6,200,000				€ 5.5	$ 5,900,000	€ 5.2
Manufacturing and Supply Agreement | Fresenius | Measurement Input, Discount Rate
Licenses Agreements [Line Items]
Manufacturing and development obligations, discount rate							9.72