STOCKHOLDERS' EQUITY (Tables)

9 Months Ended

Sep. 30, 2018

Stockholders' Equity Note [Abstract]

Schedule of Stock by Class

The following table presents the number of shares authorized and issued as of the dates indicated:

	September 30, 2018		December 31, 2017
	Shares Authorized	Shares Issued	Shares Authorized	Shares Issued
Stockholders’ equity:
Common stock, $0.000001 par value	200,000,000	84,375,021	200,000,000	83,724,916
Undesignated Preferred Stock	10,000,000	—	10,000,000	—

Schedule of Stock Option Activity

A summary of stock option activity for the nine months ended September 30, 2018 is as follows:

	Options Outstanding
	Number of Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding - December 31, 2017	7,078,932		$	22.70	5.56	$	145,613
Granted	685,850		43.52
Exercised	(737,986	)	19.91
Canceled	(109,361	)	48.85
Outstanding - September 30, 2018	6,917,435		$	24.65	5.38	$	174,842
Options vested and exercisable as of September 30, 2018	5,543,179		$	21.71	4.60	$	157,306

Schedule of RSU Activity

A summary of RSU activity for the nine months ended September 30, 2018 is as follows:

	Restricted Stock Units
	Number of Shares		Weighted-Average Grant Date Fair Value
Unvested - December 31, 2017	7,249,205		$	34.57
Granted	3,029,151		42.59
Released	(2,393,407	)	36.06
Canceled	(1,087,920	)	36.02
Unvested - September 30, 2018	6,797,029		$	37.39

Schedule of Stock-Based Compensation Expense

The following table summarizes the effects of stock-based compensation expense related to stock-based awards in the condensed consolidated statements of operations during the periods presented (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Cost of revenue	$	1,162	$	993	$	3,345	$	2,931
Sales and marketing	7,941		7,305		23,514		21,434
Product development	14,536		11,976		41,878		34,428
General and administrative	5,555		5,035		16,995		16,214
Total stock-based compensation	$	29,194	$	25,309	$	85,732	$	75,007