COMMITMENTS AND CONTINGENCIES	12 Months Ended
Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	7. COMMITMENTS AND CONTINGENCIES Securities Lawsuits We and certain of our officers were named as defendants in two purported class action securities lawsuits filed in the United States District Court for the Northern District of California, or the California District Court, as well as a third securities lawsuit, not styled as a class action, which was originally filed in the United States District Court for the Southern District of Mississippi, but subsequently transferred to the California District Court. These three cases, or the Class Action Lawsuits, which were based on the same factual background, were consolidated for all purposes. On July 21, 2017, the California District Court entered an order and final judgment that dismissed with prejudice and released the claims asserted in the Class Action Lawsuits against all named defendants in connection with the Class Action Lawsuits, including us, and any claims that could have been asserted that arise or relate to the facts alleged in the Class Action Lawsuits, such that every member of the settlement class will be barred from asserting such claims in the future. In connection with the settlement of the Class Action Lawsuits, in April 2017, we paid $250,000 and our insurance providers paid $6,000,000 to a settlement escrow account to be paid to members of the settlement class, less payment of attorneys’ fees and costs to plaintiff’s counsel. The settlement does not constitute any admission of fault or wrongdoing by us or any of the individual defendants. We do not expect to make any additional payments for and do not expect, and are not aware of, any additional claims arising from or related to the facts alleged in the Class Action Lawsuits and asserted by stockholders who have opted out of the settlement class in the Class Action Lawsuits. However, it is possible that additional lawsuits may be filed, or allegations may be made by stockholders, with respect to these same or other matters and also naming us and/or our officers and directors as defendants. Monitoring, initiating and defending against legal actions is time-consuming for our management, is likely to be expensive and may detract from our ability to fully focus our internal resources on our business activities. In addition, despite the availability of insurance, we may incur substantial legal fees and costs in connection with any additional litigation and such amounts could be material to our financial statements. We may expend significant resources in the settlement or defense of any additional lawsuits, and we may not prevail in such lawsuits. We have not established any reserve for any potential liability relating to any additional lawsuits. Indemnifications to Officers and Directors Our corporate bylaws require that we indemnify our officers and directors, as well as those who act as directors and officers of other entities at our request, against expenses, judgments, fines, settlements and other amounts actually and reasonably incurred in connection with any proceedings arising out of their services to Geron. In addition, we have entered into separate indemnification agreements with each of our directors and officers which provide for indemnification of these directors and officers under similar circumstances and under additional circumstances. The indemnification obligations are more fully described in our bylaws and the indemnification agreements. We purchase standard insurance to cover claims or a portion of the claims made against our directors and officers. Since a maximum obligation is not explicitly stated in our bylaws or in our indemnification agreements and will depend on the facts and circumstances that arise out of any future claims, the overall maximum amount of the obligations cannot be reasonably estimated. Operating Lease Commitment On September 21, 2017, we amended the lease agreement for our premises at 149 Commonwealth Drive, Menlo Park, California, to extend the lease term from February 2018 through January 2020. As of December 31, 2017, operating lease obligations under the amended lease agreement include aggregate future minimum payments of approximately $1,435,000, of which payments of approximately $678,000, $699,000 and $58,000 are due in 2018, 2019 and 2020, respectively. Rent expense under our operating leases was approximately $691,000, $708,000 and $878,000 for the years ended December 31, 2017, 2016 and 2015, respectively. 7. COMMITMENTS AND CONTINGENCIES (Continued) Severance Plan We have an Amended and Restated Severance Plan, or Severance Plan, that applies to all employees that are not subject to performance improvement plans, and provides for, among other benefits: (i) a severance payment upon a Change of Control Triggering Event and Separation from Service and (ii) a severance payment for each non‑executive employee upon a Non‑Change of Control Triggering Event and Separation from Service. As defined in the Severance Plan, a Change of Control Triggering Event and Separation from Service requires a “double trigger” where: (i) an employee is terminated by us without cause in connection with a change of control or within 12 months following a change of control provided, however, that if an employee is terminated by us in connection with a change of control but immediately accepts employment with our successor or acquirer, the employee will not be eligible for the benefits outlined in the Severance Plan, (ii) an employee resigns because in connection with a change of control, the offered terms of employment (new or continuing) by us or our successor or acquirer within 30 days after the change of control results in a material change in the terms of employment, or (iii) after accepting (or continuing) employment with us after a change of control, an employee resigns within 12 months following a change of control due to a material change in the terms of employment. Under the Severance Plan, a Non‑Change of Control Triggering Event and Separation from Service is defined as an event where a non‑executive employee is terminated by us without cause. Severance payments range from two to 18 months of base salary, depending on the employee’s position with us, payable in a lump sum payment. The Severance Plan also provides that the provisions of employment agreements entered into between us and executive or non‑executive employees supersede the provisions of the Severance Plan. As of December 31, 2017, all our executive officers have employment agreements with provisions that may provide greater severance benefits than those in the Severance Plan.

7. COMMITMENTS AND CONTINGENCIES

Securities Lawsuits

We and certain of our officers were named as defendants in two purported class action securities lawsuits filed in the United States District Court for the Northern District of California, or the California District Court, as well as a third securities lawsuit, not styled as a class action, which was originally filed in the United States District Court for the Southern District of Mississippi, but subsequently transferred to the California District Court. These three cases, or the Class Action Lawsuits, which were based on the same factual background, were consolidated for all purposes.

On July 21, 2017, the California District Court entered an order and final judgment that dismissed with prejudice and released the claims asserted in the Class Action Lawsuits against all named defendants in connection with the Class Action Lawsuits, including us, and any claims that could have been asserted that arise or relate to the facts alleged in the Class Action Lawsuits, such that every member of the settlement class will be barred from asserting such claims in the future. In connection with the settlement of the Class Action Lawsuits, in April 2017, we paid $250,000 and our insurance providers paid $6,000,000 to a settlement escrow account to be paid to members of the settlement class, less payment of attorneys’ fees and costs to plaintiff’s counsel. The settlement does not constitute any admission of fault or wrongdoing by us or any of the individual defendants.

We do not expect to make any additional payments for and do not expect, and are not aware of, any additional claims arising from or related to the facts alleged in the Class Action Lawsuits and asserted by stockholders who have opted out of the settlement class in the Class Action Lawsuits. However, it is possible that additional lawsuits may be filed, or allegations may be made by stockholders, with respect to these same or other matters and also naming us and/or our officers and directors as defendants. Monitoring, initiating and defending against legal actions is time-consuming for our management, is likely to be expensive and may detract from our ability to fully focus our internal resources on our business activities. In addition, despite the availability of insurance, we may incur substantial legal fees and costs in connection with any additional litigation and such amounts could be material to our financial statements. We may expend significant resources in the settlement or defense of any additional lawsuits, and we may not prevail in such lawsuits. We have not established any reserve for any potential liability relating to any additional lawsuits.

Indemnifications to Officers and Directors

Our corporate bylaws require that we indemnify our officers and directors, as well as those who act as directors and officers of other entities at our request, against expenses, judgments, fines, settlements and other amounts actually and reasonably incurred in connection with any proceedings arising out of their services to Geron. In addition, we have entered into separate indemnification agreements with each of our directors and officers which provide for indemnification of these directors and officers under similar circumstances and under additional circumstances. The indemnification obligations are more fully described in our bylaws and the indemnification agreements. We purchase standard insurance to cover claims or a portion of the claims made against our directors and officers. Since a maximum obligation is not explicitly stated in our bylaws or in our indemnification agreements and will depend on the facts and circumstances that arise out of any future claims, the overall maximum amount of the obligations cannot be reasonably estimated.

Operating Lease Commitment

On September 21, 2017, we amended the lease agreement for our premises at 149 Commonwealth Drive, Menlo Park, California, to extend the lease term from February 2018 through January 2020. As of December 31, 2017, operating lease obligations under the amended lease agreement include aggregate future minimum payments of approximately $1,435,000, of which payments of approximately $678,000, $699,000 and $58,000 are due in 2018, 2019 and 2020, respectively. Rent expense under our operating leases was approximately $691,000, $708,000 and $878,000 for the years ended December 31, 2017, 2016 and 2015, respectively.

7. COMMITMENTS AND CONTINGENCIES (Continued)

Severance Plan

We have an Amended and Restated Severance Plan, or Severance Plan, that applies to all employees that are not subject to performance improvement plans, and provides for, among other benefits: (i) a severance payment upon a Change of Control Triggering Event and Separation from Service and (ii) a severance payment for each non‑executive employee upon a Non‑Change of Control Triggering Event and Separation from Service. As defined in the Severance Plan, a Change of Control Triggering Event and Separation from Service requires a “double trigger” where: (i) an employee is terminated by us without cause in connection with a change of control or within 12 months following a change of control provided, however, that if an employee is terminated by us in connection with a change of control but immediately accepts employment with our successor or acquirer, the employee will not be eligible for the benefits outlined in the Severance Plan, (ii) an employee resigns because in connection with a change of control, the offered terms of employment (new or continuing) by us or our successor or acquirer within 30 days after the change of control results in a material change in the terms of employment, or (iii) after accepting (or continuing) employment with us after a change of control, an employee resigns within 12 months following a change of control due to a material change in the terms of employment. Under the Severance Plan, a Non‑Change of Control Triggering Event and Separation from Service is defined as an event where a non‑executive employee is terminated by us without cause. Severance payments range from two to 18 months of base salary, depending on the employee’s position with us, payable in a lump sum payment. The Severance Plan also provides that the provisions of employment agreements entered into between us and executive or non‑executive employees supersede the provisions of the Severance Plan. As of December 31, 2017, all our executive officers have employment agreements with provisions that may provide greater severance benefits than those in the Severance Plan.