Debt instrument, available amount upon condition.

No definition available.

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Namespace Prefix:	cers_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt instrument interest only payments date.

+ References

No definition available.

+ Details

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Namespace Prefix:	cers_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument principal and declining interest payments additional period.

+ References

No definition available.

+ Details

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- Definition

Debt prepayment fee.

+ References

No definition available.

+ Details

Name:	cers_DebtPrepaymentFee
Namespace Prefix:	cers_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Expiration date to draw second tranche.

+ References

No definition available.

+ Details

Name:	cers_ExpirationDateToDrawSecondTranche
Namespace Prefix:	cers_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Interest only payment period.

+ References

No definition available.

+ Details

Name:	cers_InterestOnlyPaymentPeriod
Namespace Prefix:	cers_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of equal tranches.

+ References

No definition available.

+ Details

Name:	cers_NumberOfEqualTranches
Namespace Prefix:	cers_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Repayments principal and interest aggregate amount.

+ References

No definition available.

+ Details

Name:	cers_RepaymentsPrincipalAndInterestAggregateAmount
Namespace Prefix:	cers_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Trailing net revenue target.

+ References

No definition available.

+ Details

Name:	cers_TrailingNetRevenueTarget
Namespace Prefix:	cers_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
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-Section 55
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-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
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-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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-Paragraph 4
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-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 210
-SubTopic 10
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-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Balance Type:	na
Period Type:	instant

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
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-Paragraph 15
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Debt - Additional Information (Detail)	Mar. 29, 2019 USD ($) Tranche	Jul. 31, 2017 USD ($) Tranche	Jun. 30, 2019 USD ($)
Oxford Term Loan Agreement \| 2017 Term Loans
Debt Instrument [Line Items]
Term loan, face amount		$ 40,000,000.0
Number of loan tranches \| Tranche		2
Repayments principal and interest aggregate amount	$ 31,200,000
Prepayment fees in aggregate amount	600,000
Oxford Term Loan Agreement \| 2017 Term Loans \| Interest Expense
Debt Instrument [Line Items]
Extinguishment loss recorded	2,100,000
Cerus Term Loans \| 2017 Term Loans
Debt Instrument [Line Items]
Repay in full all of outstanding term loans		$ 1,400,000
Term Loan Credit Agreement
Debt Instrument [Line Items]
Term loan, face amount	$ 70,000,000
Number of loan tranches \| Tranche	3
Debt instrument maturity date	Mar. 01, 2024
Term Loan Credit Agreement \| Two Thousand Nineteen Term Loan
Debt Instrument [Line Items]
Debt instrument floating interest rate percentage	1.80%
Effective interest rate			8.10%
Interest-only payments date	Apr. 01, 2022
Principal plus declining interest payments	24 months
Interest only payment period	12 months
Trailing net revenue target period	12 months
Revolving Loan Credit Agreement
Debt Instrument [Line Items]
Term loan, face amount	$ 5,000,000.0		$ 4,500,000
Loan and security agreement available upon revenue achievement	$ 15,000,000.0
Debt instrument floating interest rate percentage	1.80%
Revolving Loan Credit Agreement \| Two Thousand Nineteen Term Loan
Debt Instrument [Line Items]
Debt instrument maturity date	Mar. 01, 2024
First Tranche (Term Loan A) \| Oxford Term Loan Agreement \| 2017 Term Loans
Debt Instrument [Line Items]
Term loan, face amount		30,000,000.0
First Tranche (Term Loan A) \| Cerus Term Loans \| 2017 Term Loans
Debt Instrument [Line Items]
Repay in full all of outstanding term loans		17,600,000
Second Tranche (Term Loan B) \| Oxford Term Loan Agreement \| 2017 Term Loans
Debt Instrument [Line Items]
Loan and security agreement available upon revenue achievement		$ 10,000,000.0
Expiration date to draw second tranche		May 14, 2018
Tranche 1 \| Term Loan Credit Agreement
Debt Instrument [Line Items]
Term loan, face amount	$ 40,000,000.0
Tranche 2 \| Term Loan Credit Agreement \| Two Thousand Nineteen Term Loan
Debt Instrument [Line Items]
Loan and security agreement available upon revenue achievement	15,000,000.0
Tranche 3 \| Term Loan Credit Agreement \| Two Thousand Nineteen Term Loan
Debt Instrument [Line Items]
Loan and security agreement available upon revenue achievement	$ 15,000,000.0