Subsequent Events	6 Months Ended
Jun. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	Note 14. Subsequent Events Loan and Security Agreement On July 31, 2017, the Company entered into an Amended and Restated Loan and Security Agreement (the “Restated Term Loan Agreement”) with Oxford Finance LLC (“Oxford”), as collateral agent, and the lenders party thereto, which amends and restates in its entirety the Company’s prior Term Loan Agreement (See Note 7). The Restated Term Loan Agreement provides for secured growth capital loans of up to $40.0 million (the “Term Loans”). All of the Company’s current and future assets, excluding its intellectual property and 35% of the Company’s investment in Cerus Europe B.V., are secured for its borrowings under the Restated Term Loan Agreement. On July 31, 2017, the Company received $30.0 million from the first tranche under the Restated Term Loan Agreement, and settled its prior Term Loan Agreement. The second tranche of $10.0 million will be available subject to the Company achieving consolidated trailing six months’ revenue at a specified threshold no later than January 31, 2019. The Term Loans shall be interest-only through February 1, 2019 followed by 42 months of equal principal and interest. However, if the Company draws the Term Loan Two, then the interest-only period will be extended through August 1, 2019, and the amortization period will be reduced to 36 months. All of the Term Loans mature on July 1, 2022 (the “Maturity Date”). The interest rate of the term loans is 6.72% plus the index rate, which is floating and will be reset monthly as the greater of (i) 8.01% and (ii) the sum of the three-month U.S. LIBOR rate plus (b) 6.72%. The Company will also be required to make a final payment fee of 8.00% of the amounts of the Term Loans drawn payable on the earlier of (i) the prepayment of the Term Loans or (ii) the Maturity Date. The term loans contain certain financial covenants. Sales Agreement On August 4, 2017, the Company entered into Amendment No. 3 (“Amendment No. 3”) to the Controlled Equity Offering^SM Sales Agreement, dated August 31, 2012, as previously amended on March 21, 2014 and May 5, 2016 (as amended, the “Amended Cantor Agreement”) with Cantor. In connection with Amendment No. 3, the Company intends to file a new shelf registration statement on Form S-3 (the “New Registration Statement”). Amendment No. 3 will become effective upon the effectiveness of the New Registration Statement. As amended by Amendment No. 3, the Amended Cantor Agreement will provide for the issuance and sale of shares of the Company’s common stock following the effectiveness of the New Registration Statement having an aggregate offering price of up to $70.0 million through Cantor, which amount includes any unsold shares of Common Stock previously available for sale under the Amended Cantor Agreement prior to the effectiveness of the New Registration Statement. The Company can make no assurance regarding the initial or continued effectiveness of the New Registration Statement.

Note 14. Subsequent Events

Loan and Security Agreement

On July 31, 2017, the Company entered into an Amended and Restated Loan and Security Agreement (the “Restated Term Loan Agreement”) with Oxford Finance LLC (“Oxford”), as collateral agent, and the lenders party thereto, which amends and restates in its entirety the Company’s prior Term Loan Agreement (See Note 7). The Restated Term Loan Agreement provides for secured growth capital loans of up to $40.0 million (the “Term Loans”). All of the Company’s current and future assets, excluding its intellectual property and 35% of the Company’s investment in Cerus Europe B.V., are secured for its borrowings under the Restated Term Loan Agreement. On July 31, 2017, the Company received $30.0 million from the first tranche under the Restated Term Loan Agreement, and settled its prior Term Loan Agreement. The second tranche of $10.0 million will be available subject to the Company achieving consolidated trailing six months’ revenue at a specified threshold no later than January 31, 2019. The Term Loans shall be interest-only through February 1, 2019 followed by 42 months of equal principal and interest. However, if the Company draws the Term Loan Two, then the interest-only period will be extended through August 1, 2019, and the amortization period will be reduced to 36 months. All of the Term Loans mature on July 1, 2022 (the “Maturity Date”). The interest rate of the term loans is 6.72% plus the index rate, which is floating and will be reset monthly as the greater of (i) 8.01% and (ii) the sum of the three-month U.S. LIBOR rate plus (b) 6.72%. The Company will also be required to make a final payment fee of 8.00% of the amounts of the Term Loans drawn payable on the earlier of (i) the prepayment of the Term Loans or (ii) the Maturity Date. The term loans contain certain financial covenants.

Sales Agreement

On August 4, 2017, the Company entered into Amendment No. 3 (“Amendment No. 3”) to the Controlled Equity Offering^SM Sales Agreement, dated August 31, 2012, as previously amended on March 21, 2014 and May 5, 2016 (as amended, the “Amended Cantor Agreement”) with Cantor. In connection with Amendment No. 3, the Company intends to file a new shelf registration statement on Form S-3 (the “New Registration Statement”). Amendment No. 3 will become effective upon the effectiveness of the New Registration Statement. As amended by Amendment No. 3, the Amended Cantor Agreement will provide for the issuance and sale of shares of the Company’s common stock following the effectiveness of the New Registration Statement having an aggregate offering price of up to $70.0 million through Cantor, which amount includes any unsold shares of Common Stock previously available for sale under the Amended Cantor Agreement prior to the effectiveness of the New Registration Statement. The Company can make no assurance regarding the initial or continued effectiveness of the New Registration Statement.