Common Stock and Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2020

Common Stock and Stockholders'Equity

Assumptions used for estimate of fair value of options

	Quarters Ended March 31,
	2020		2019
Volatility		46.1% – 47.9%		47.5% – 47.6%
Expected life (in years)		4.3		5.4
Risk-free interest rate		0.87% - 1.64%		2.50% - 2.55%
Dividend yield		–		–
Weighted-average fair value of underlying stock options	$	42.06	$	27.87

Schedule of activity under the RSUs

Activity under the RSUs is as follows:

		Weighted-Average
		Grant Date
	Shares	Fair Value Per Share
Balance at December 31, 2019	1,483,558	$	54.13
Granted	321,311	$	122.96
Vested and issued	(455,956)	$	51.79
Forfeited	(54,476)	$	48.78
Balance at March 31, 2020	1,294,437	$	58.82
Vested and unissued at March 31, 2020	13,755	$	50.90
Non-vested at March 31, 2020	1,280,682	$	58.91

Schedule of activity under the PSUs

Activity under the PSU is as follows:

		Weighted-Average
		Grant Date
	Shares	Fair Value Per Share
Balance at December 31, 2019	512,482	$	62.51
Granted	111,199	$	117.81
Vested and issued	(186,455)	$	62.02
Balance at March 31, 2020	437,226	$	76.78
Vested and unissued at March 31, 2020	0	$	0
Non-vested at March 31, 2020	437,226	$	76.78

Components of operating expense charged for compensation cost expense

Total compensation costs charged as an expense for stock-based awards, including stock options, RSU’s and ESPP, recognized in the components of operating expenses are as follows (in thousands):

	Quarter Ended
	March 31,
	2020		2019
Administrative and marketing	$	1,259	$	821
Sales		2,919		2,130
Technology and development		2,104		1,898
General and administrative		12,033		8,674
Total stock-based compensation expense	$	18,315	$	13,523

Summary of activity

Activity under the Plan is as follows (in thousands, except share and per share amounts and years):

				Weighted-
		Weighted-		Average
	Number of	Average		Remaining	Aggregate
	Shares	Exercise		Contractual	Intrinsic
	Outstanding	Price		Life in Years	Value
Balance at December 31, 2019	5,206,981	$	24.47	7.03	$	308,538
Stock option grants	7,441	$	106.25	0	$	0
Stock options exercised	(671,279)	$	22.10	0	$	(65,192)
Stock options forfeited	(126,577)	$	34.48	0	$	0
Balance at March 31, 2020	4,416,566	$	24.67	6.77	$	575,408
Vested or expected to vest at March 31, 2020	4,414,765	$	24.67	6.77	$	575,408
Exercisable at March 31, 2020	3,055,075	$	19.80	6.41	$	413,071