Carrying value as of the balance sheet date of obligations incurred and payable to collaboration partner for which invoices have not yet been received under the respective collaboration agreement (due within one year or within the normal operating cycle if longer).

No definition available.

COLLABORATION AND LICENSE AGREEMENT (Details)		3 Months Ended	12 Months Ended
COLLABORATION AND LICENSE AGREEMENT (Details)	Dec. 15, 2014 USD ($) item	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
LICENSE AGREEMENTS
Revenues from collaborative agreements		$ 35,000,000	$ 35,000,000
Accrued collaboration charges			$ 2,328,000
License agreements \| Janssen Biotech \| Initial Period
LICENSE AGREEMENTS
Upfront payment received	$ 35,000,000
Number of agreed upon studies \| item	2
Percentage of costs to be paid by Geron	50.00%
Percentage of costs to be paid by Janssen	50.00%
Notification period	24 months
Maximum period Geron is obligated to procure supply for manufacturing imetelstat under collaboration agreement	9 months
License agreements \| Janssen Biotech \| U.S. Opt-In Rights exercised
LICENSE AGREEMENTS
Percentage of costs to be paid by Geron	20.00%
Percentage of costs to be paid by Janssen	80.00%
Continuation Election milestone payment	$ 65,000,000
Aggregate maximum total payments for development and regulatory milestones under collaboration agreement	470,000,000
Aggregate maximum total of payments for sales milestones under collaboration agreement	$ 350,000,000
Tiered royalties percentage, low end of the range	mid-teens
Tiered royalties percentage, high end of the range	low twenties
U.S. selling effort percentage	20.00%
License agreements \| Janssen Biotech \| U.S. Opt-In Rights not exercised
LICENSE AGREEMENTS
Continuation Election milestone payment	$ 65,000,000
Full U.S. Rights fee	70,000,000
Aggregate maximum total payments for development and regulatory milestones under collaboration agreement	415,000,000
Aggregate maximum total of payments for sales milestones under collaboration agreement	$ 350,000,000
Tiered royalties percentage, low end of the range	double-digit
Tiered royalties percentage, high end of the range	mid-teens
License agreements \| Janssen Biotech \| Collaborative Arrangement IP Exclusively Licensed
LICENSE AGREEMENTS
Percentage of costs to be paid by Geron	50.00%
Percentage of costs to be paid by Janssen	50.00%