Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement [Abstract]

Summary of Stock Option Activity and Weighted Average Exercise Prices

A summary of the Company’s stock option activity and weighted average exercise prices follows:

	Stock Option Activity			Weighted Average Remaining Contractual Term (In years)	Aggregate Intrinsic Value (In thousands)
	Options (In thousands)	Weighted Average Exercise Price
Balances outstanding at December 31, 2020	4,332	$	19.78	6.79	$	183,825
Granted	472
Exercised	(461)
Cancelled or expired	(88)
Balances outstanding at June 30, 2021	4,255	24.21		6.85	166,339
Options vested and expected to vest	1,187	32.09		8.25	37,185
Options exercisable at June 30, 2021	2,448	$	16.58	5.66	$	114,235

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity

A summary of the Company’s restricted stock unit (“RSU”) activity and weighted average exercise prices follows:

	Restricted Stock Unit Activity
	Number of Shares (In thousands)	Weighted Average Grant Date Fair Value (Per share)		Aggregate Fair Value (In thousands)
Balances outstanding at December 31, 2020	2,950	$	27.00	$	183,781
Awarded	1,565
Vested	(1,244)
Forfeited	(250)
Non-vested and outstanding at June 30, 2021	3,021	$	38.46	$	191,205
Expected to vest	1,841	$	36.30	$	116,404

Weighted Average Assumptions of Fair Value Options Using Black-Scholes Option-Pricing Model

The fair value of each option grant is estimated on the date of grant, adjusted for estimated forfeitures, using the Black-Scholes option-pricing model with the following weighted average assumptions:

	Three Months Ended		Six Months Ended
	June 30,		June 30,
	2021	2020	2021	2020
Dividend yield	0.00%	0.00%	0.00%	0.00%
Risk-free interest rate	0.77% -0.84%	0.31% - 0.32%	0.46% - 0.84%	0.31% - 0.66%
Expected life (in years)	5	5	5	5
Historical volatility	54.31% - 54.55%	51.91% - 51.94%	53.94% - 54.55%	46.50% - 51.94%