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STOCKHOLDERS' EQUITY - SALES AGREEMENT (Details) | Aug. 28, 2015 USD ($)
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STOCKHOLDERS' EQUITY |
Aggregate offering price of common stock | $ 50,000,000
Maximum commission rate (as a percent) | 3.00%

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- Definition Represents the aggregate offering price for which the entity may elect to issue and sell shares of its common stock under the sales agreement. + References No definition available. + Details
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Namespace Prefix: | gern_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Represents the percentage of maximum commission rate, based on gross proceeds of sale price per share of common stock sold through MLV & Co. under the sales agreement. + References No definition available. + Details
Name: | gern_MaximumCommissionRate
Namespace Prefix: | gern_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_StockholdersEquityNoteAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration