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v2.4.1.9

FAIR VALUE MEASUREMENTS (Details) (USD $) In Thousands, unless otherwise specified | Mar. 31, 2015 | Dec. 31, 2014
--- | --- | ---
Included in cash and cash equivalents |  |
Amortized Cost | $ 7,231 us-gaap_CashEquivalentsAtCarryingValue | $ 40,342 us-gaap_CashEquivalentsAtCarryingValue
Estimated Fair Value | 7,231 us-gaap_CashAndCashEquivalentsFairValueDisclosure | 40,342 us-gaap_CashAndCashEquivalentsFairValueDisclosure
Restricted cash |  |
Amortized Cost | 266 us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue | 266 us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue
Estimated Fair Value | 266 us-gaap_RestrictedInvestmentsAtFairValue | 266 us-gaap_RestrictedInvestmentsAtFairValue
Marketable securities |  |
Amortized Cost | 153,411 us-gaap_AvailableForSaleSecuritiesAmortizedCost | 127,661 us-gaap_AvailableForSaleSecuritiesAmortizedCost
Gross Unrealized Gains | 45 gern_GrossUnrealizedGainsAvailableForSaleSecurities | 16 gern_GrossUnrealizedGainsAvailableForSaleSecurities
Gross Unrealized Losses | (62)gern_GrossUnrealizedLossesAvailableForSaleSecurities | (100)gern_GrossUnrealizedLossesAvailableForSaleSecurities
Estimated Fair Value | 153,394 us-gaap_AvailableForSaleSecurities | 127,577 us-gaap_AvailableForSaleSecurities
Money market funds |  |
Included in cash and cash equivalents |  |
Amortized Cost | 7,231 us-gaap_CashEquivalentsAtCarryingValue / us-gaap_InvestmentTypeAxis = us-gaap_MoneyMarketFundsMember | 40,342 us-gaap_CashEquivalentsAtCarryingValue / us-gaap_InvestmentTypeAxis = us-gaap_MoneyMarketFundsMember
Estimated Fair Value | 7,231 us-gaap_CashAndCashEquivalentsFairValueDisclosure / us-gaap_InvestmentTypeAxis = us-gaap_MoneyMarketFundsMember | 40,342 us-gaap_CashAndCashEquivalentsFairValueDisclosure / us-gaap_InvestmentTypeAxis = us-gaap_MoneyMarketFundsMember
Certificates of deposit |  |
Restricted cash |  |
Amortized Cost | 266 us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_InvestmentTypeAxis = us-gaap_CertificatesOfDepositMember | 266 us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_InvestmentTypeAxis = us-gaap_CertificatesOfDepositMember
Estimated Fair Value | 266 us-gaap_RestrictedInvestmentsAtFairValue / us-gaap_InvestmentTypeAxis = us-gaap_CertificatesOfDepositMember | 266 us-gaap_RestrictedInvestmentsAtFairValue / us-gaap_InvestmentTypeAxis = us-gaap_CertificatesOfDepositMember
Government-sponsored enterprise securities (due in less than 1 year) |  |
Marketable securities |  |
Amortized Cost | 401 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInLessThanOneYearMember | 401 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInLessThanOneYearMember
Gross Unrealized Losses | (1)gern_GrossUnrealizedLossesAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInLessThanOneYearMember | (1)gern_GrossUnrealizedLossesAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInLessThanOneYearMember
Estimated Fair Value | 400 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInLessThanOneYearMember | 400 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInLessThanOneYearMember
Government-sponsored enterprise securities (due in 1 to 2 years) |  |
Marketable securities |  |
Amortized Cost | 5,806 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInOneToTwoYearsMember | 6,556 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInOneToTwoYearsMember
Gross Unrealized Losses | (1)gern_GrossUnrealizedLossesAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInOneToTwoYearsMember | (7)gern_GrossUnrealizedLossesAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInOneToTwoYearsMember
Estimated Fair Value | 5,805 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInOneToTwoYearsMember | 6,549 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInOneToTwoYearsMember
Commercial paper (due in less than 1 year) |  |
Marketable securities |  |
Amortized Cost | 28,963 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = gern_CommercialPaperDueInLessThanOneYearMember | 10,985 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = gern_CommercialPaperDueInLessThanOneYearMember
Gross Unrealized Gains | 33 gern_GrossUnrealizedGainsAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CommercialPaperDueInLessThanOneYearMember | 14 gern_GrossUnrealizedGainsAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CommercialPaperDueInLessThanOneYearMember
Estimated Fair Value | 28,996 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CommercialPaperDueInLessThanOneYearMember | 10,999 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CommercialPaperDueInLessThanOneYearMember
Corporate notes (due in less than 1 year) |  |
Marketable securities |  |
Amortized Cost | 106,305 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInLessThanOneYearMember | 97,307 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInLessThanOneYearMember
Gross Unrealized Gains | 10 gern_GrossUnrealizedGainsAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInLessThanOneYearMember | 2 gern_GrossUnrealizedGainsAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInLessThanOneYearMember
Gross Unrealized Losses | (56)gern_GrossUnrealizedLossesAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInLessThanOneYearMember | (63)gern_GrossUnrealizedLossesAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInLessThanOneYearMember
Estimated Fair Value | 106,259 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInLessThanOneYearMember | 97,246 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInLessThanOneYearMember
Corporate notes (due in 1 to 2 years) |  |
Marketable securities |  |
Amortized Cost | 11,936 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInOneToTwoYearsMember | 12,412 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInOneToTwoYearsMember
Gross Unrealized Gains | 2 gern_GrossUnrealizedGainsAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInOneToTwoYearsMember |
Gross Unrealized Losses | (4)gern_GrossUnrealizedLossesAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInOneToTwoYearsMember | (29)gern_GrossUnrealizedLossesAvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInOneToTwoYearsMember
Estimated Fair Value | $ 11,934 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInOneToTwoYearsMember | $ 12,383 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = gern_CorporateNoteSecuritiesDueInOneToTwoYearsMember

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