Development and License Agreements - Additional Information (Detail) € in Millions	1 Months Ended	3 Months Ended		9 Months Ended			12 Months Ended
	Jun. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2017 EUR (€)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 EUR (€)	Sep. 30, 2017 EUR (€)	Dec. 31, 2016 USD ($)	Dec. 31, 2016 EUR (€)
Licenses Agreements [Line Items]
Payments made relating to the manufacturing of the products		$ 3,000,000	$ 4,800,000	$ 9,400,000		$ 11,800,000
BARDA Agreement
Licenses Agreements [Line Items]
Committed fund receivable	$ 88,200,000
Committed fund receivable	$ 186,200,000
Period of agreement	5 years
Accounts receivable of billed and unbilled amounts		2,000,000		2,000,000					$ 1,000,000
Other current assets
Licenses Agreements [Line Items]
Research and development assets		200,000		200,000					900,000
Amounts due from Fresenius		1,000,000		1,000,000					300,000
Other assets
Licenses Agreements [Line Items]
Research and development assets		2,200,000		2,200,000					2,000,000
Manufacturing efficiency assets		1,900,000		1,900,000					2,100,000
Fresenius
Licenses Agreements [Line Items]
Allocated amount for research and development activities		4,800,000		4,800,000
Manufacturing efficiency activity cost		2,400,000		2,400,000
Cerus Corporation | BARDA Agreement
Licenses Agreements [Line Items]
Co-investment by the company	$ 5,000,000
Additional co-investment by the company	$ 9,600,000
Manufacturing and Supply Agreement
Licenses Agreements [Line Items]
Accrual for manufacturing of entity products		6,000,000		6,000,000					3,000,000
Manufacturing and Supply Agreement | Fresenius
Licenses Agreements [Line Items]
Payments made based on the successful achievement of production volumes | €							€ 8.6
Accrual for manufacturing and development of entity products		$ 5,600,000		$ 5,600,000				€ 4.8	$ 4,800,000	€ 4.5
Manufacturing and development obligations, discount rate				9.72%	9.72%
Manufacturing and development payments				$ 3,400,000	€ 3.1