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 March 31, 2020, there was a total of 12.1 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	1.3		114.33
Forfeited	(0.1	)	68.19
Vested	(1.0	)	58.17
Balance—March 31, 2020	6.3		$	75.96

As of March 31, 2020, total compensation expense related to unvested RSUs granted to employees and non-employees under the 2009 Plan, but not yet recognized, was $440.8 million. This expense is expected to be amortized on a straight-line basis over a weighted-average 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. Total payment of the employees’ tax obligations to the tax authorities is reflected as a financing activity within the condensed consolidated statements of cash flows.



	Three Months Ended
	March 31, 2020		March 31, 2019
Shares withheld for taxes	0.3		0.4
Amount withheld for taxes	$	37.8	$	32.0



	Three Months Ended
	March 31, 2020		March 31, 2019
Expected term in years	4.4		4.4
Volatility	33.5	%	34.2	%
Risk-free interest rate	1.3	%	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	0.5		114.48
Forfeited	—		59.28
Exercised	(0.2	)	40.02
Balance—March 31, 2020	3.0		$	62.41
Options vested and expected to vest—March 31, 2020	3.0		$	62.41	4.8	$	123.8
Options exercisable—March 31, 2020	1.5		$	39.50	3.5	$	90.3

The aggregate intrinsic value represents the difference between the exercise price of stock options and the quoted market price of our common stock on March 31, 2020 for all in-the-money stock options. As of March 31, 2020, total compensation expense related to unvested stock options granted to employees but not yet recognized was $38.6 million. This expense is expected to be amortized on a straight-line basis over a weighted-average period of 3.1 years.

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



	Three Months Ended
	March 31, 2020		March 31, 2019
Weighted-average fair value per share granted	$	33.82	$	27.12
Intrinsic value of options exercised	$	13.1	$	27.2
Fair value of options vested	$	6.0	$	4.2

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
	March 31, 2020		March 31, 2019
Cost of product revenue	$	0.4	$	0.4
Cost of service revenue	3.0		2.8
Research and development	10.9		9.4
Sales and marketing	25.7		25.4
General and administrative	5.3		5.0
Total stock-based compensation expense	$	45.3	$	43.0

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
	March 31, 2020		March 31, 2019
RSUs	$	42.2	$	39.2
Stock options	3.1		2.5
ESPP	—		1.3
Total stock-based compensation expense	$	45.3	$	43.0

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
	March 31, 2020		March 31, 2019
Income tax benefit associated with stock-based compensation	$	10.0	$	10.0

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 months ended March 31, 2020, we repurchased 10.0 million shares of common stock under the Repurchase Program in open market transactions at an average price of $90.36 per share and for an aggregate purchase price of $899.9 million. As of March 31, 2020, $692.9 million remained available for future share repurchases under the Repurchase Program.