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Stockholders' Equity (Deficit) - Summary of Number of Shares of Common Stock Reserved (Detail)	Dec. 31, 2014	Dec. 31, 2013
Class Of Stock [Line Items]
Reserved shares of common stock	3,689,767us-gaap_CommonStockCapitalSharesReservedForFutureIssuance	8,156,461us-gaap_CommonStockCapitalSharesReservedForFutureIssuance
Common stock options [Member]
Class Of Stock [Line Items]
Reserved shares of common stock	3,561,104us-gaap_CommonStockCapitalSharesReservedForFutureIssuance / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember	1,201,770us-gaap_CommonStockCapitalSharesReservedForFutureIssuance / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember
Redeemable Convertible Preferred Stock [Member]
Class Of Stock [Line Items]
Reserved shares of common stock		6,954,691us-gaap_CommonStockCapitalSharesReservedForFutureIssuance / us-gaap_StatementEquityComponentsAxis = us-gaap_RedeemableConvertiblePreferredStockMember
Warrants to Purchase Common Stock [Member]
Class Of Stock [Line Items]
Reserved shares of common stock	128,663us-gaap_CommonStockCapitalSharesReservedForFutureIssuance / us-gaap_StatementEquityComponentsAxis = ceru_WarrantsToPurchaseCommonStockMember

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- Definition

Aggregate number of common shares reserved for future issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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