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v2.4.1.9

Commitments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Operating Leased Assets [Line Items] |  |  |
Noncancelable operating lease expire date | Feb. 28, 2013 |  |
Noncancelable operating leases renewal option period | 3 years |  |
Deferred liability related to facility lease | $ 41 us-gaap_DeferredRentCredit | $ 12 us-gaap_DeferredRentCredit |
Lease amendment, commencement Date | 2014-07-15 |  |
Noncancelable operating lease rent expenses | $ 766 us-gaap_LeaseAndRentalExpense | $ 598 us-gaap_LeaseAndRentalExpense | $ 517 us-gaap_LeaseAndRentalExpense
Extended Lease |  |  |
Operating Leased Assets [Line Items] |  |  |
Noncancelable operating lease expire date | Feb. 28, 2016 |  |

X
- Definition Lease commencement date. + References No definition available. + Details
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Namespace Prefix: | ceru_
Data Type: | us-types:dateStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense over the term of the leased property by the lessor or lessee, respectively. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=7501430&loc=d3e39896-112707 + Details
Name: | us-gaap_DeferredRentCredit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line. + References No definition available. + Details
Name: | us-gaap_LeaseAndRentalExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Date which lease or group of leases is set to expire, in CCYY-MM-DD format. + References No definition available. + Details
Name: | us-gaap_LeaseExpirationDate1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Term of the lessee's leasing arrangement renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_LesseeLeasingArrangementsOperatingLeasesRenewalTerm
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_OperatingLeasedAssetsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_LeaseArrangementTypeAxis=ceru_ExtendedLeaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |