We maintain the Amended and Restated Fortinet, Inc. 2009 Equity Incentive Plan (the “Amended Plan”) pursuant to which we have granted RSUs and stock options. We also previously had an Employee Stock Purchase Plan (“ESPP”) for eligible employees, which was terminated in February 2019. As of June 30, 2020, there was a total of 12.0 million shares of common stock available for grant under the Amended Plan.

The following table summarizes the activity and related information for RSUs for the periods presented below (in millions, except per share amounts):


	Restricted Stock Units Outstanding
	Number of Shares	Weighted-Average Grant Date Fair Value per Share
Balance—December 31, 2019	6.1	$	64.56
Granted	1.6	120.02
Forfeited	(0.2)	72.69
Vested	(1.7)	56.98
Balance—June 30, 2020	5.8	$	81.49

Stock compensation expense is recognized on a straight-line basis over the vesting period of each RSU. As of June 30, 2020, total compensation expense related to unvested RSUs granted to employees and non-employees under the 2009 Plan, but not yet recognized, was $427.5 million, with a weighted-average remaining vesting period of 2.9 years.

RSUs settle into shares of common stock upon vesting. Upon the vesting of the RSUs, we net-settle the RSUs and withhold a portion of the shares to satisfy minimum statutory employee withholding tax requirements. The payment of the withheld taxes to the tax authorities is reflected as a financing activity within the condensed consolidated statements of cash flows.


	Three Months Ended						Six Months Ended
	June 30, 2020		June 30, 2019		June 30, 2020		June 30, 2019
Shares withheld for taxes	0.2		0.3		0.5		0.7
Amount withheld for taxes	$	21.1	$	24.5	$	58.9	$	56.5


	Three Months Ended						Six Months Ended
	June 30, 2020		June 30, 2019		June 30, 2020		June 30, 2019
Expected term in years	4.4		4.4		4.4		4.4
Volatility	39.0	%	34.4	%	34.4	%	34.2	%
Risk-free interest rate	0.3	%	2.2	%	1.1	%	2.5	%
Dividend rate	—	%	—	%	—	%	—	%

The following table summarizes the stock option activity and related information for the periods presented below (in millions, except exercise prices and contractual life):


	Options Outstanding
	Number of Shares	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Balance—December 31, 2019	2.7	$	50.37
Granted	0.6	118.50
Forfeited	—	80.97
Exercised	(0.4)	40.78
Balance—June 30, 2020	2.9	$	66.01
Options vested and expected to vest—June 30, 2020	2.9	$	66.01	4.7	$	206.0
Options exercisable—June 30, 2020	1.4	$	41.09	3.5	$	134.3

The aggregate intrinsic value represents the difference between the exercise price of stock options and the quoted market price of our common stock on June 30, 2020 for all in-the-money stock options. Stock compensation expense is recognized on a straight-line basis over the vesting period of each stock option. As of June 30, 2020, total compensation expense related to unvested stock options granted to employees but not yet recognized was $38.5 million, with a weighted-average remaining vesting period of 3.0 years.

Additional information related to our stock options is summarized below (in millions, except per share amounts):


	Three Months Ended						Six Months Ended
	June 30, 2020		June 30, 2019		June 30, 2020		June 30, 2019
Weighted-average fair value per share granted	$	46.92	$	26.38	$	35.51	$	27.08

Intrinsic value of options exercised	$	17.3	$	9.6	30.4		36.8
Fair value of options vested	$	2.4	$	2.0	8.4		6.2

Stock-based compensation expense, including stock-based compensation expense related to awards classified as liabilities, is included in costs and expenses as follows (in millions):


	Three Months Ended						Six Months Ended
	June 30, 2020		June 30, 2019		June 30, 2020		June 30, 2019
Cost of product revenue	$	0.4	$	0.4	$	0.8	$	0.8
Cost of service revenue	3.2		2.9		6.2		5.7
Research and development	12.0		10.0		22.9		19.4
Sales and marketing	27.9		26.3		53.6		51.7
General and administrative	6.1		5.4		11.4		10.4
Total stock-based compensation expense	$	49.6	$	45.0	$	94.9	$	88.0

The following table summarizes stock-based compensation expense, including stock-based compensation expense related to awards classified as liabilities, by award type (in millions):


	Three Months Ended						Six Months Ended
	June 30, 2020		June 30, 2019		June 30, 2020		June 30, 2019
RSUs	$	45.9	$	41.9	$	88.1	$	81.1
Stock options	3.7		3.1		6.8		5.6
ESPP	—		—		—		1.3
Total stock-based compensation expense	$	49.6	$	45.0	$	94.9	$	88.0

Total income tax benefit associated with stock-based compensation that is recognized in the condensed consolidated statements of income is as follows (in millions):


	Three Months Ended						Six Months Ended
	June 30, 2020		June 30, 2019		June 30, 2020		June 30, 2019
Income tax benefit associated with stock-based compensation	$	10.9	$	10.4	$	20.9	$	20.4

Under the Share Repurchase Program originally approved by our board of directors in January 2016 (the “Repurchase Program”), our board of directors has authorized the repurchase of up to $2.5 billion of our outstanding common stock through February 28, 2021. Share repurchases may be made by us from time to time in privately negotiated transactions or in open market transactions. The Repurchase Program does not require us to purchase a minimum number of shares, and may be suspended, modified or discontinued at any time without prior notice.

During the three and six months ended June 30, 2020, we repurchased 1.4 million and 11.4 million shares of common stock, respectively, under the Repurchase Program in open market transactions at an average price of $99.69 per share and $91.55 per share, respectively, for an aggregate purchase price of $146.1 million and $1.0 billion, respectively. As of June 30, 2020, $546.8 million remained available for future share repurchases under the Repurchase Program.