Debt instrument, available amount upon condition.

No definition available.

Name:	cers_DebtInstrumentAvailableAmountUponCondition
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

Name:	cers_DebtInstrumentInterestOnlyPaymentsDate
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

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

- 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

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
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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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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-Topic 210
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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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Namespace Prefix:	us-gaap_
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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Namespace Prefix:	us-gaap_
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))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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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Namespace Prefix:	us-gaap_
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
-SubTopic 50
-Section 40
-Paragraph 4
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-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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Namespace Prefix:	us-gaap_
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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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Period Type:	instant

- Details

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Debt - Additional Information (Detail)	Mar. 29, 2019 USD ($) Tranche	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
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		7.50%
Interest-only payments date	Mar. 01, 2022
Principal plus declining interest payments	24 months
Interest only payment period	12 months
Trailing net revenue target period	12 months
Term Loan Credit Agreement \| Tranche 1
Debt Instrument [Line Items]
Term loan, face amount	$ 40,000,000.0
Term Loan Credit Agreement \| Tranche 2 \| Two Thousand Nineteen Term Loan
Debt Instrument [Line Items]
Loan and security agreement available upon revenue achievement	15,000,000.0
Term Loan Credit Agreement \| Tranche 3 \| Two Thousand Nineteen Term Loan
Debt Instrument [Line Items]
Loan and security agreement available upon revenue achievement	15,000,000.0
Prior Loan Agreement \| 2017 Term Loans
Debt Instrument [Line Items]
Repayments principal and interest aggregate amount	31,200,000
Prepayment fees in aggregate amount	600,000
Prior Loan Agreement \| Interest Expense \| 2017 Term Loans
Debt Instrument [Line Items]
Extinguishment loss recorded	2,100,000
Revolving Loan Credit Agreement
Debt Instrument [Line Items]
Term loan, face amount	5,000,000.0	$ 4,800,000	$ 5,000,000.0
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