STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Jun. 30, 2020

Share-based Payment Arrangement [Abstract]

The fair value of each option is based on the assumptions in the following table:


	Three Months Ended June 30,			Six Months Ended June 30,
	2020	2019	2020	2019
Option Plan Shares
Risk-free interest rates	(1)	(1)	0.98% - 1.47%	2.54% - 2.59%
Expected term (in years)	(1)	(1)	4.68 - 6.15	6.28
Expected volatility	(1)	(1)	65.67% - 77.51%	64.95% - 65.00%
Dividend yield	(1)	(1)	—%	—%
Weighted average fair value per share of options granted during the period	(1)	(1)	$58.77	$57.11
ESPP Shares
Risk-free interest rates	0.12% - 0.2%	2.31% - 2.44%	0.12% - 0.2%	2.31% - 2.44%
Expected term (in years)	0.5 - 2	0.5 - 2	0.5 - 2	0.5 - 2
Expected volatility	63.7% - 89.0%	55.0% - 57.6%	63.7% - 89.0%	55.0% - 57.6%
Dividend yield	—%	—%	—%	—%
Weighted average fair value per share of stock purchase rights granted during the period	$30.60	$35.91	$30.60	$35.91

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(1)The Company did not grant options under its 2010 Omnibus Long-Term Incentive Plan or 2019 Omnibus Long-Term Incentive Plan during the period indicated.

Summary of stock option activity under the Stock Plans

A summary of stock option activity under the Stock Plans during the six months ended June 30, 2020 is as follows:


Options	Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term(Years)	Aggregate Intrinsic Value(1)
(Aggregate intrinsic value in thousands)
Outstanding, January 1, 2020	2,700,293	$	34.01	2.9
Granted	309,143	97.66
Exercised	(368,720)	29.67
Forfeited	(65,438)	83.87
Outstanding, June 30, 2020	2,575,278	$	41.01	6.5	$	123,979
Exercisable, June 30, 2020	1,653,394	$	26.10	5.5	$	101,761

Summary of restricted stock and restricted stock unit activity under the Stock Plans

A summary of restricted stock and restricted stock unit activity under the Stock Plans during the six months ended June 30, 2020 is as follows:


	Restricted Shares and RSUs	Weighted Average Grant Date Fair Value
Outstanding, January 1, 2020	4,384,005	$	63.41
Granted	1,835,695	92.25
Released	(1,350,088)	47.00
Forfeited	(208,076)	79.45
Outstanding, June 30, 2020	4,661,536	$	78.84