Note 11. Equity

a. Stock-based compensation plans

Stock-based compensation expenses for equity-classified stock options and restricted stock units ("RSUs") were allocated as follows:

A summary of the Company’s stock option activity for the six months ended June 30, 2018 is as follows:

The outstanding options generally have a term of ten years from the grant date. Options granted become exercisable over the vesting period, which is normally a four-year period beginning on the grant date, subject to the employee’s continuous service to the Company. The fair value of stock options is determined using the Black-Scholes model.

During the six-month periods ended June 30, 2018 and 2017, the Company issued 20,596 shares and 140,476 shares, respectively, upon the exercise of stock options. This resulted in an increase in equity of $0.3 million and $2.2 million for the six-month periods ended June 30, 2018 and 2017, respectively.

As of June 30, 2018, the unrecognized compensation cost of $14.4 million related to all unvested, equity-classified stock options is expected to be recognized as an expense over a weighted-average period of 2.4 years.

A summary of the Company’s RSUs activity for the six months ended June 30, 2018 is as follows:

The fair value of RSUs is determined based on the quoted price of the Company’s ordinary shares on the date of the grant.

As of June 30, 2018, the unrecognized compensation cost of $22.6 million related to all unvested, equity-classified RSUs is expected to be recognized as expense over a weighted-average period of 3.3 years.

b. Accumulated other comprehensive loss

The following tables present the changes in the components of accumulated other comprehensive income (loss), net of taxes, for the six months ended June 30, 2018 and 2017, respectively: