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Stockholders Equity - Additional Information (Detail) (USD $)
 12 Months Ended 1 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Nov. 30, 2010
Jun. 12, 2014
Aug. 31, 2009
Stockholders Equity Note [Line Items]            
Common stock, par value $ 0.001us-gaap_CommonStockParOrStatedValuePerShare $ 0.001us-gaap_CommonStockParOrStatedValuePerShare     $ 0.001us-gaap_CommonStockParOrStatedValuePerShare  
Common stock, shares authorized 225,000,000us-gaap_CommonStockSharesAuthorized 112,500,000us-gaap_CommonStockSharesAuthorized     112,500,000us-gaap_CommonStockSharesAuthorized  
Warrant liability $ 10,485,000us-gaap_WarrantsAndRightsOutstanding $ 20,390,000us-gaap_WarrantsAndRightsOutstanding        
Proceeds from common stock sold 18,488,000us-gaap_ProceedsFromIssuanceOfCommonStock 61,425,000us-gaap_ProceedsFromIssuanceOfCommonStock 14,226,000us-gaap_ProceedsFromIssuanceOfCommonStock      
2009 Unit Offering            
Stockholders Equity Note [Line Items]            
Warrants to purchase an aggregate shares of common stock           2,400,000us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_ClassOfWarrantOrRightAxis
= cers_TwoThousandNineUnitOfferingMember
Warrant exercise price           $ 2.90us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= cers_TwoThousandNineUnitOfferingMember
Warrant liability 0us-gaap_WarrantsAndRightsOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= cers_TwoThousandNineUnitOfferingMember		          
2010 Unit Offering            
Stockholders Equity Note [Line Items]            
Warrants to purchase an aggregate shares of common stock       3,700,000us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_ClassOfWarrantOrRightAxis
= cers_TwoThousandTenUnitOfferingMember		    
Warrant exercise price       3.20us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= cers_TwoThousandTenUnitOfferingMember		    
Warrant liability 3,300,000us-gaap_WarrantsAndRightsOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= cers_TwoThousandTenUnitOfferingMember		          
2010 Unit Offering | Warrant            
Stockholders Equity Note [Line Items]            
Warrants exercisable date       May 15, 2011    
Exercisable period       5 years    
Warrants exercised 2,600,000cers_WarrantsExercised
/ us-gaap_ClassOfWarrantOrRightAxis
= cers_TwoThousandTenUnitOfferingMember
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_WarrantMember		 200,000cers_WarrantsExercised
/ us-gaap_ClassOfWarrantOrRightAxis
= cers_TwoThousandTenUnitOfferingMember
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_WarrantMember		 5,000cers_WarrantsExercised
/ us-gaap_ClassOfWarrantOrRightAxis
= cers_TwoThousandTenUnitOfferingMember
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_WarrantMember		      
Stockholder Rights Plan            
Stockholders Equity Note [Line Items]            
Minimum percentage of common stock acquired by stockholders 15.00%cers_MinimumPercentageOfCommonStockAcquiredByStockholders
/ us-gaap_StatementClassOfStockAxis
= cers_StockholderRightsPlanMember		          
Designated preferred stock for future issuance 250,000cers_DesignatedPreferredStockForFutureIssuance
/ us-gaap_StatementClassOfStockAxis
= cers_StockholderRightsPlanMember		          
Sales Agreement | Cantor            
Stockholders Equity Note [Line Items]            
Maximum common stock offering price 70,000,000cers_MaximumAmountAvailableUnderOffering
/ dei_LegalEntityAxis
= cers_CantorMember
/ us-gaap_StatementClassOfStockAxis
= cers_SalesAgreementMember		          
Percentage of proceeds payable as compensation to underwriter 2.00%cers_PercentageOfProceedsPayableAsCompensationToUnderwriter
/ dei_LegalEntityAxis
= cers_CantorMember
/ us-gaap_StatementClassOfStockAxis
= cers_SalesAgreementMember		          
Common stock, number of shares issued 4,300,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ dei_LegalEntityAxis
= cers_CantorMember
/ us-gaap_StatementClassOfStockAxis
= cers_SalesAgreementMember		 5,400,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ dei_LegalEntityAxis
= cers_CantorMember
/ us-gaap_StatementClassOfStockAxis
= cers_SalesAgreementMember		        
Proceeds from common stock sold 18,600,000us-gaap_ProceedsFromIssuanceOfCommonStock
/ dei_LegalEntityAxis
= cers_CantorMember
/ us-gaap_StatementClassOfStockAxis
= cers_SalesAgreementMember		 23,500,000us-gaap_ProceedsFromIssuanceOfCommonStock
/ dei_LegalEntityAxis
= cers_CantorMember
/ us-gaap_StatementClassOfStockAxis
= cers_SalesAgreementMember		        
Common stock available for sale $ 22,500,000cers_CommonStockSharesAvailableForSaleValue
/ dei_LegalEntityAxis
= cers_CantorMember
/ us-gaap_StatementClassOfStockAxis
= cers_SalesAgreementMember