Equity Incentive Plans and Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

A summary of shares available for grant under the Company’s plans is as follows:


			Shares Available for Grant







Total shares available for grant as of December 31, 2017			5,051,147
Increase in shares approved for issuance			5,500,000
Stock options granted			(711,479)
Stock options forfeited			877,803

Nonvested equity stock and stock units granted (1) (2)			(4,993,802)
Nonvested equity stock and stock units forfeited (1)			4,350,377
Total shares available for grant as of December 31, 2018			10,074,046
Increase in shares approved for issuance (3)			400,000
Stock options granted			(80,000)
Stock options forfeited			426,960

Nonvested equity stock and stock units granted (1) (4)			(7,261,845)
Nonvested equity stock and stock units forfeited (1)			3,267,702
Total shares available for grant as of December 31, 2019			6,826,863
Increase in shares approved for issuance (5)			7,800,000
Stock options granted			(40,000)
Stock options forfeited			101,816

Nonvested equity stock and stock units granted (1) (6)			(3,528,401)
Nonvested equity stock and stock units forfeited (1)			1,252,042
Total shares available for grant as of December 31, 2020			12,412,320

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(1) For purposes of determining the number of shares available for grant under the 2015 Plan against the maximum number of shares authorized, each restricted stock granted reduces the number of shares available for grant by 1.5 shares and each restricted stock forfeited increases shares available for grant by 1.5 shares.

(2) Amount includes 0.5 million shares that had been reserved for potential future issuance related to certain performance unit awards discussed under the section titled “Nonvested Equity Stock and Stock Units” below.

(3) Shares were reserved under the 2019 Inducement Plan adopted in the third quarter of 2019.

(4) Amount includes 1.0 million shares that have been reserved for potential future issuance related to certain performance unit awards discussed under the section titled “Nonvested Equity Stock and Stock Units” below.

(5) On April 30, 2020, the Company’s stockholders approved an additional 7,800,000 shares for issuance under the 2015 Plan.

(6) Amount includes 0.5 million shares that have been reserved for potential future issuance related to certain performance unit awards discussed under the section titled “Nonvested Equity Stock and Stock Units” below.

Schedule of stock option activity

The following table summarizes stock option activity under the Company’s equity incentive plans for the years ended December 31, 2020, 2019 and 2018 and information regarding stock options outstanding, exercisable, and vested and expected to vest as of December 31, 2020:


	Options Outstanding			Weighted-Average Remaining Contractual Term
(In thousands, except per share amounts and years)	Number of Shares	Weighted-Average Exercise Price per Share			Aggregate Intrinsic Value





Outstanding as of December 31, 2017	4,310,361	$	9.78
Options granted	711,479	$	12.84
Options exercised	(908,146)	$	6.70
Options forfeited	(877,803)	$	13.73

Outstanding as of December 31, 2018	3,235,891	$	10.25
Options granted	80,000	$	13.25
Options exercised	(1,249,785)	$	7.79
Options forfeited	(426,960)	$	13.71
Outstanding as of December 31, 2019	1,639,146	$	11.37
Options granted	40,000	$	15.59
Options exercised	(613,119)	$	10.74
Options forfeited	(101,816)	$	19.41
Outstanding as of December 31, 2020	964,211	$	11.08	5.04	$	6,151
Vested or expected to vest at December 31, 2020	961,925	$	11.08	5.03	$	6,143
Options exercisable at December 31, 2020	781,102	$	10.51	4.31	$	5,432

Weighted-average assumptions for stock option plan

The following table presents the weighted-average assumptions used to estimate the fair value of stock options granted that contain only service conditions in the periods presented:


	Stock Option Plan for Years Ended December 31,
	2020	2019	2018
Stock Option Plan
Expected stock price volatility	38%	33%-36%	24%-32%
Risk free interest rate	0.2%	1.4%-1.6%	2.6%-2.8%
Expected term (in years)	5.5	5.1-5.2	5.8
Weighted-average fair value of stock options granted	$5.46	$4.36	$4.23

Weighted-average assumptions for employee stock purchase plan


	Employee Stock Purchase Plan for Years Ended December 31,
	2020	2019	2018
Employee Stock Purchase Plan
Expected stock price volatility	37%-46%	32%	27%-34%
Risk free interest rate	0.1%	1.6%-2.4%	2.05%-2.5%
Expected term (in years)	0.5	0.5	0.5
Weighted-average fair value of purchase rights granted under the purchase plan	$3.46	$3.13	$2.59

Schedule of nonvested equity stock and stock units activity

The following table reflects the activity related to nonvested equity stock and stock units for the three years ended December 31, 2020:


Nonvested Equity Stock and Stock Units	Shares	Weighted-Average Grant-Date Fair Value




Nonvested at December 31, 2017	5,861,349	$	12.68
Granted	2,978,558	$	12.77
Vested	(1,713,930)	$	12.39
Forfeited	(2,266,842)	$	12.97
Nonvested at December 31, 2018	4,859,135	$	12.71
Granted	4,233,701	$	10.17
Vested	(1,896,283)	$	12.40
Forfeited	(1,907,070)	$	11.33
Nonvested at December 31, 2019	5,289,483	$	11.27
Granted	1,986,117	$	15.60
Vested	(1,693,659)	$	11.70
Forfeited	(730,676)	$	11.83
Nonvested at December 31, 2020	4,851,265	$	12.82