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STOCK PLANS AND SHARE BASED COMPENSATION | 12 Months Ended
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Dec. 31, 2020
Share-based Payment Arrangement [Abstract] |
STOCK PLANS AND SHARE BASED COMPENSATION [Text Block] | 7. STOCK PLANS AND SHARE BASED COMPENSATION: The share and per share information for all periods presented in this Form 10-K has been adjusted for the effect of the August 2020 stock split. Refer to Note 10, Earnings Per Share, in this Form 10-K for details. Stock Plans As of December 31, 2020, the Company had three stock-based compensation plans (the “Plans”) which are described below. 2007 Equity Incentive Plan The 2007 Equity Incentive Plan (2007 Plan) was adopted by the board of directors on September 10, 2007, and approved by the stockholders on November 7, 2007, as an amendment and restatement of the 1997 Stock Option Plan (1997 Plan). The 2007 Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock unit (RSU) awards, stock appreciation rights, performance-based (PSU) awards, long-term performance based (PRSU) awards and other stock awards to employees, directors and consultants. Pursuant to the 2007 Plan, the exercise price for incentive stock options and non-statutory stock options is generally at least 100% of the fair market value of the underlying shares on the date of grant. Options generally vest over 48 months measured from the date of grant. Options generally expire no later than ten years after the date of grant, subject to earlier termination upon an optionee’s cessation of employment or service. The 2007 Plan expired in September 2017 with no further grants to be made under this plan; however previous grants under this plan shall remain outstanding until they are exercised, vest, forfeited or expire. 2016 Incentive Award Plan The 2016 Incentive Award Plan (2016 Plan) was adopted by the board of directors on March 17, 2016 and approved by the stockholders on May 13, 2016. The 2016 Plan provides for the grant of RSU awards, PSU awards and PRSU awards. No other forms of equity-based awards, including stock options and stock appreciation rights, may be granted under the 2016 Plan. As of December 31, 2020, 2.2 million awards have been issued and approximately 2.8 million shares of common stock remain available for future grant under the 2016 Plan. 1997 Employee Stock Purchase Plan Under the 1997 Employee Stock Purchase Plan (Purchase Plan), eligible employees may apply accumulated payroll deductions, which may not exceed 15% of an employee’s compensation, to the purchase of shares of the Company’s common stock at periodic intervals. The purchase price of stock under the Purchase Plan is equal to 85% of the lower of (i) the fair market value of the Company’s common stock on the first day of each offering period, or (ii) the fair market value of the Company’s common stock on the purchase date (as defined in the Purchase Plan). Each offering period consists of one purchase period of approximately six months' duration. An aggregate of 7.0 million shares of common stock were reserved for issuance to employees under the Purchase Plan. As of December 31, 2020, of the shares reserved for issuance, 6.6 million shares had been purchased and 0.4 million shares were reserved for future issuance under the Purchase Plan. Shares Reserved As of December 31, 2020, the Company had approximately 3.4 million shares of common stock reserved for future grant under all stock plans. Stock-Based Compensation The Company applies the provisions of ASC 718-10, Stock Compensation. Under the provisions of ASC 718-10, the Company recognizes the fair value of stock-based compensation in its financial statements over the requisite service period of the individual grants, which generally equals a four-year vesting period. The Company uses estimates of volatility, expected term, risk-free interest rate, dividend yield and forfeitures in determining the fair value of these awards and the amount of compensation expense to recognize. The Company uses the straight-line method to amortize all stock awards granted over the requisite service period of the award. The following table summarizes the stock-based compensation expense recognized in accordance with ASC 718-10 for the years ended December 31, 2020, 2019 and 2018:
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2020 |  | 2019 |  | 2018
Cost of revenues | ​ | $ | 1,963 | ​ | $ | 1,237 | ​ | $ | 1,097
Research and development | ​ |  | 10,378 | ​ |  | 8,423 | ​ |  | 7,688
Sales and marketing | ​ |  | 6,290 | ​ |  | 5,015 | ​ |  | 4,729
General and administrative | ​ |  | 12,281 | ​ |  | 8,672 | ​ |  | 8,066
Total stock-based compensation expense | ​ | $ | 30,912 | ​ | $ | 23,347 | ​ | $ | 21,580
​ The following table summarizes total compensation expense related to unvested awards not yet recognized, net of expected forfeitures, and the weighted average period over which it is expected to be recognized as of December 31, 2020:
​ | ​ | ​ | ​ | ​ | ​
​ |  | Unrecognized Compensation |  | Weighted Average
​ | ​ | Expense for Unvested | ​ | Remaining Recognition
​ | ​ | Awards | ​ | Period
​ | ​ | (In thousands) | ​ | (In years)
Long-term performance-based awards | ​ | $ | 5,810 |  | 1.64
Restricted stock units | ​ |  | 34,654 |  | 2.62
Purchase plan | ​ |  | 202 |  | 0.08
Total unrecognized compensation expense | ​ | $ | 40,666 |  |
​ Stock-based compensation expense in the year ended December 31, 2020, was approximately $30.9 million (comprising approximately $18.7 million related to restricted stock units, $10.2 million related to performance-based awards and $2.0 million related to the Company’s Purchase Plan). Stock-based compensation expense in the year ended December 31, 2019, was approximately $23.3 million (comprising approximately $17.5 million related to restricted stock units, $4.1 million related to performance-based awards and $1.7 million related to the Company’s Purchase Plan). Stock-based compensation expense in the year ended December 31, 2018, was approximately $21.6 million comprising approximately $16.6 million related to restricted stock units, $3.4 million related to performance-based awards and $1.6 million related to the Company’s Purchase Plan). The Company did not grant stock options in the years ended December 31, 2020, 2019 and 2018, and therefore no fair-value assumptions are reported. The fair value of employees’ stock purchase rights under the Purchase Plan was estimated using the Black-Scholes model with the following weighted-average assumptions used during the three years ended December 31, 2020, 2019 and 2018:
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31, |
​ |  | 2020 | ​ | 2019 | ​ | 2018
Risk-free interest rates |  | ​ | 0.90 | % | ​ | ​ | 2.28 | % | ​ | ​ | 1.94 | %
Expected volatility rates |  | ​ | 47 | % | ​ | ​ | 37 | % | ​ | ​ | 31 | %
Expected dividend yield |  | ​ | 0.78 | % | ​ | ​ | 0.91 | % | ​ | ​ | 0.89 | %
Expected term of purchase rights (in years) |  | ​ | 0.50 |  | ​ | ​ | 0.50 |  | ​ | ​ | 0.50 |
Weighted-average estimated fair value of purchase rights | ​ | $ | 15.73 | ​ | ​ | $ | 19.39 | ​ | ​ | $ | 17.33 | ​
​ A summary of stock options outstanding as of December 31, 2020, and activity during three years then ended, is presented below:
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | Weighted- | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | Average | ​ | ​ | ​
​ | ​ | ​ | ​ | Weighted- | ​ | Remaining | ​ | ​ | ​
​ | ​ | ​ | ​ | Average | ​ | Contractual | ​ | Aggregate
​ | ​ | Shares | ​ | Exercise | ​ | Term | ​ | Intrinsic Value
​ |  | (In thousands) |  | Price |  | (In years) |  | (In thousands)
Outstanding at January 1, 2018 |  | 1,022 | ​ | $ | 14.52 |  |  |  | ​ |
Granted |  | — | ​ |  | — |  |  |  | ​ |
Exercised |  | (352) | ​ | $ | 11.30 |  |  |  | ​ |
Forfeited or expired |  | — | ​ |  | — |  |  |  | ​ |
Outstanding at December 31, 2018 |  | 670 | ​ | $ | 16.21 |  |  |  | ​ |
Granted |  | — | ​ |  | — |  |  |  | ​ |
Exercised |  | (335) | ​ | $ | 12.98 |  |  |  | ​ |
Forfeited or expired |  | — | ​ |  | — |  |  |  | ​ |
Outstanding at December 31, 2019 |  | 335 | ​ | $ | 19.44 |  |  |  | ​ |
Granted |  | — | ​ |  | — |  |  |  | ​ |
Exercised |  | (243) | ​ | $ | 18.99 |  |  |  | ​ |
Forfeited or expired |  | — | ​ |  | — |  |  |  | ​ |
Outstanding at December 31, 2020 |  | 92 | ​ | $ | 20.63 |  | 1.05 | ​ | $ | 5,643
Vested and Exercisable at December 31, 2020 |  | 92 | ​ |  | ​ | ​ | 1.05 | ​ | $ | 5,643
​ The total intrinsic value of options exercised during the year ended December 31, 2020, 2019 and 2018, was $9.1 million, $8.3 million and $7.5 million, respectively. The following table summarizes the stock options outstanding at December 31, 2020:
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Options Outstanding | ​ | Options Exercisable
​ |  | ​ |  | Weighted Average |  | Weighted |  | ​ |  | Weighted
​ | ​ | ​ | ​ | Remaining | ​ | Average | ​ | ​ | ​ | Average
(shares in thousands) | ​ | Options | ​ | Contractual Term | ​ | Exercise | ​ | Options | ​ | Exercise
Range of Exercise Prices | ​ | Outstanding | ​ | (in years) | ​ | Price | ​ | Exercisable | ​ | Price
$18.48 - $19.75 | ​ | 28 | ​ | 0.38 | ​ | $ | 18.77 | ​ | 28 | ​ | $ | 18.77
$21.44 - $21.44 |  | 64 |  | 1.35 | ​ | $ | 21.44 |  | 64 | ​ | $ | 21.44
​ |  | 92 |  | 1.05 | ​ | $ | 20.63 |  | 92 | ​ | $ | 20.63
​ PSU Awards Under the performance-based awards program, the Company grants awards in the performance year in an amount equal to twice the target number of shares to be issued if the maximum performance metrics are met. The number of shares that are released at the end of the performance year can range from zero to 200% of the target number depending on the Company’s performance. The performance metrics of this program are annual targets consisting of a combination of net revenue, non-GAAP operating earnings and strategic goals. As the net revenue, non-GAAP operating income and strategic goals are considered performance conditions, expense associated with these awards, net of estimated forfeitures, is recognized over the service period based on an assessment of the achievement of the performance targets. The fair value of these PSUs is determined using the fair value of the Company’s common stock on the date of the grant, reduced by the discounted present value of dividends expected to be declared before the awards vest. If the performance conditions are not achieved, no compensation cost is recognized and any previously recognized compensation is reversed. A summary of PSU awards outstanding as of December 31, 2020, and activity during the three years then ended, is presented below: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | Weighted- | ​ | ​ | ​
​ | ​ | ​ | ​ | Weighted- | ​ | Average | ​ | ​ | ​
​ | ​ | ​ | ​ | Average | ​ | Remaining | ​ | Aggregate
​ | ​ | Shares | ​ | Grant Date Fair | ​ | Contractual Term | ​ | Intrinsic Value
​ |  | (In thousands) |  | Value Per Share |  | (In years) |  | (In thousands)
Outstanding at January 1, 2018 |  | 158 | ​ | $ | 32.00 |  |  |  | ​ |
Granted |  | 178 | ​ | $ | 31.44 |  |  |  | ​ |
Vested |  | (158) | ​ | $ | 32.00 |  |  |  | ​ |
Forfeited or canceled |  | (126) | ​ | $ | 31.44 |  |  |  | ​ |
Outstanding at December 31, 2018 |  | 52 | ​ | $ | 31.44 |  |  |  | ​ |
Granted |  | 185 | ​ | $ | 35.06 |  |  |  | ​ |
Vested |  | (52) | ​ | $ | 31.44 |  |  |  | ​ |
Forfeited or canceled |  | (64) | ​ | $ | 35.06 |  |  |  | ​ |
Outstanding at December 31, 2019 |  | 121 | ​ | $ | 35.06 |  |  |  | ​ |
Granted |  | 150 | ​ | $ | 46.31 |  |  |  | ​ |
Vested |  | (121) | ​ | $ | 35.06 |  |  |  | ​ |
Forfeited or canceled |  | — | ​ | ​ | — |  |  |  | ​ |
Outstanding at December 31, 2020 |  | 150 | ​ | $ | 46.27 |  | — | ​ | $ | 12,219
Outstanding and expected to vest at December 31, 2020 |  | 150 | ​ |  | ​ | ​ | — | ​ | $ | 12,219
​ The grant-date fair value of PSU awards released, which were fully vested, in the years ended December 31, 2020, 2019 and 2018 was approximately $4.2 million, $1.6 million and $5.1 million, respectively. PRSU Awards (Long-term Performance Based) The Company’s PRSU program provides for the issuance of PRSUs which will vest based on the Company’s performance measured against the PRSU Plan’s established revenue targets. The PRSUs were granted in an amount equal to twice the target number of shares to be issued if the maximum performance metrics are met. The actual number of shares the recipient receives is determined at the end of a three-year performance period based on results achieved versus the Company’s performance goals, and may range from zero to 200% of the target number. Recipients of a PRSU award generally must remain employed by the Company on a continuous basis through the end of the applicable three-year performance period in order to receive shares subject to that award. The performance goals for PRSUs granted in fiscal 2020, 2019 and 2018 were based on the Company’s annual revenue growth over the respective three-year performance period. Expense associated with these awards, net of estimated forfeitures, is recorded throughout the year based on an assessment of the expected achievement of the performance targets. If the performance conditions are not achieved, no compensation cost is recognized and any previously recognized compensation is reversed. A summary of PRSU awards outstanding as of December 31, 2020, and activity during the three years then ended, is presented below:
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | Weighted-Average | ​ | Aggregate
​ | ​ | ​ | ​ | Weighted-Average | ​ | Remaining | ​ | Intrinsic
​ | ​ | Shares | ​ | Grant Date Fair | ​ | Contractual Term | ​ | Value
​ |  | (In thousands) |  | Value Per Share |  | (In years) |  | (In thousands)
Outstanding at January 1, 2018 |  | 368 | ​ | $ | 26.40 |  |  |  | ​ |
Granted |  | 144 | ​ | $ | 29.95 |  |  |  | ​ |
Vested |  | (76) | ​ | $ | 26.23 |  |  |  | ​ |
Forfeited or canceled |  | (10) | ​ | $ | 21.63 |  |  |  | ​ |
Outstanding at December 31, 2018 |  | 426 | ​ | $ | 27.74 |  |  |  | ​ |
Granted |  | 144 | ​ | $ | 34.09 |  |  |  | ​ |
Vested |  | (140) | ​ | $ | 21.63 |  |  |  | ​ |
Forfeited or canceled |  | (143) | ​ | $ | 31.50 |  |  |  | ​ |
Outstanding at December 31, 2019 |  | 287 | ​ | $ | 32.03 |  |  |  | ​ |
Granted |  | 152 | ​ | $ | 49.67 |  |  |  | ​ |
Vested |  | — | ​ | ​ | — |  |  |  | ​ |
Forfeited or canceled |  | (138) | ​ | $ | 29.95 |  |  |  | ​ |
Outstanding at December 31, 2020 |  | 301 | ​ | $ | 41.90 |  | 1.51 | ​ | $ | 24,637
Outstanding and expected to vest at December 31, 2020 |  | 272 | ​ |  | ​ | ​ | 1.54 | ​ | $ | 22,279
​ In January 2020 it was determined that no shares subject to the PRSUs granted in 2017 vested in aggregate; thus no shares were released to the Company’s executives in 2020. The grant-date fair value of PRSU awards released, which were fully vested, in the years ended December 31, 2019 and 2018 was approximately $3.0 million and $2.0 million, respectively. RSU Awards RSUs granted to employees typically vest ratably over a four-year period, and are converted into shares of the Company’s common stock upon vesting on a one-for-one basis subject to the employee’s continued service to the Company over that period. The fair value of RSUs is determined using the fair value of the Company’s common stock on the date of the grant, reduced by the discounted present value of dividends expected to be declared before the awards vest. Compensation expense is recognized on a straight-line basis over the requisite service period of each grant adjusted for estimated forfeitures. A summary of RSU awards outstanding as of December 31, 2020, and activity during the three years then ended, is presented below:
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | Weighted-Average | ​ | Aggregate
​ | ​ | ​ | ​ | Weighted-Average | ​ | Remaining | ​ | Intrinsic
​ | ​ | Shares | ​ | Grant Date Fair | ​ | Contractual Term | ​ | Value
​ |  | (In thousands) |  | Value Per Share |  | (In years) |  | (In thousands)
Outstanding at January 1, 2018 |  | 1,896 | ​ | $ | 27.76 |  |  |  | ​ |
Granted |  | 550 | ​ | $ | 31.43 |  |  |  | ​ |
Vested |  | (592) | ​ | $ | 26.89 |  |  |  | ​ |
Forfeited |  | (64) | ​ | $ | 29.72 |  |  |  | ​ |
Outstanding at December 31, 2018 |  | 1,790 | ​ | $ | 29.10 |  |  |  | ​ |
Granted |  | 582 | ​ | $ | 34.90 |  |  |  | ​ |
Vested |  | (603) | ​ | $ | 28.10 |  |  |  | ​ |
Forfeited |  | (50) | ​ | $ | 31.72 |  |  |  | ​ |
Outstanding at December 31, 2019 |  | 1,719 | ​ | $ | 31.33 |  |  |  | ​ |
Granted |  | 439 | ​ | $ | 44.82 |  |  |  | ​ |
Vested |  | (599) | ​ | $ | 30.25 |  |  |  | ​ |
Forfeited |  | (41) | ​ | $ | 36.77 |  |  |  | ​ |
Outstanding at December 31, 2020 |  | 1,518 | ​ | $ | 35.51 |  | 1.42 | ​ | $ | 124,239
Outstanding and expected to vest at December 31, 2020 |  | 1,423 | ​ |  | ​ | ​ | 1.36 | ​ | $ | 116,475
​ The grant-date fair value of RSUs vested in the years ended December 31, 2020, 2019 and 2018, was approximately $18.1 million, $16.9 million and $15.9 million, respectively.

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