Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Line Items]
Increase in valuation allowance	$ 13,600	$ 11,800	$ 14,100
Loss before income taxes	(62,731)	(59,539)	$ (38,560)
Operating loss carryforwards related to windfall tax deductions	2,800
Research and development tax credit carryforwards	31,777	$ 35,131
Internal Revenue Service (IRS)
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	503,000
Research and development tax credit carryforwards	$ 23,900
Internal Revenue Service (IRS) | Minimum
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2017
Research and development tax credit carryforwards, expiration year	2018
Internal Revenue Service (IRS) | Maximum
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2036
Research and development tax credit carryforwards, expiration year	2036
California Franchise Tax Board | Latest Tax Year
Income Tax Disclosure [Line Items]
Tax year remain subject to examination by the taxing jurisdictions	1998
California Franchise Tax Board | Latest Tax Year
Income Tax Disclosure [Line Items]
Tax year remain subject to examination by the taxing jurisdictions	2015
Tax and Customs Administration, Netherlands | Latest Tax Year
Income Tax Disclosure [Line Items]
Tax year remain subject to examination by the taxing jurisdictions	2013
Tax and Customs Administration, Netherlands | Latest Tax Year
Income Tax Disclosure [Line Items]
Tax year remain subject to examination by the taxing jurisdictions	2015
State and Local Jurisdiction
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 94,000
Research and development tax credit carryforwards	$ 11,900
State and Local Jurisdiction | Minimum
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2017
State and Local Jurisdiction | Maximum
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2036
Domestic Tax Authority | Latest Tax Year
Income Tax Disclosure [Line Items]
Tax year remain subject to examination by the taxing jurisdictions	1998
Domestic Tax Authority | Latest Tax Year
Income Tax Disclosure [Line Items]
Tax year remain subject to examination by the taxing jurisdictions	2015
Cerus Europe B.V.
Income Tax Disclosure [Line Items]
Undistributed earning of foreign subsidiary	$ 5,200
Unrecognized deferred tax liability for unrepatriated earnings	$ 1,900