EQUITY AWARD PLAN (Tables)

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of stock options outstanding

The following table summarizes the outstanding stock option activity (in thousands, except per share amounts and years):

	Options Outstanding
	Number of Shares	Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Balance, December 31, 2013	19,609	$	4.51	7.3	$	195,142
Options granted	1,585	13.00
Options exercised	(3,618)	2.11
Options forfeited	(534)	10.94
Balance, December 31, 2014	17,042	$	5.60	6.7	$	119,782
Options exercisable as of December 31, 2014	11,278	$	3.74	6.0	$	97,008
Options vested and expected to vest as of December 31, 2014	16,853	$	5.54	6.7	$	119,331

Summary of restricted stock units outstanding

The following table summarizes the outstanding activity of RSUs (in thousands, except per share amounts and years):

	RSUs Outstanding
	Number of Shares		Weighted Average Grant Date Fair Value Per Share		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Balance, December 31, 2013	1,011		$	17.11	1.6	$	14,356
RSUs granted	2,289		12.70
RSUs vested	(319	)	17.53
RSUs forfeited	(156	)	14.27
Balance, December 31, 2014	2,825		$	13.65	1.7	$	33,955

Summary of stock activity and number of shares available for grant

The following table summarizes the stock activity and the total number of shares available for grant under the 2012 Plan as of December 31, 2014 (in thousands):

	Number of Shares
Balance, December 31, 2013	8,547
Additional shares reserved for issuance	4,035
Options granted	(1,585	)
Options forfeited	534
RSUs granted	(2,289	)
RSUs forfeited	156
Balance, December 31, 2014	9,398

Summary of stock options, valuation assumptions

The following table summarizes the weighted average assumptions relating to the Company’s stock options:

	Years Ended December 31,
	2014		2013		2012
Volatility	60.7	%	67.4	%	69.1	%
Expected term (years)	6.1		6.1		6.0
Risk-free interest rate	1.9	%	1.9	%	1.0	%
Dividend yield	—		—		—

Summary of Employee Stock Purchase Plan, valuation assumptions

The following table summarizes the weighted average assumptions relating to the Company’s ESPP:

	Years Ended December 31,
	2014		2013
Volatility	40.2	%	59.6	%
Expected term (years)	0.7		0.7
Risk-free interest rate	0.1	%	0.1	%
Dividend yield	—		—

Schedule of allocation of stock-based compensation expense

The following table summarizes the stock-based compensation expense recorded for stock awards issued to employees and non-employees (in thousands):

	Years Ended December 31,
	2014			2013			2012
Cost of revenue	$	1,092		$	818		$	243
Research and development	9,099			6,738			2,409
Sales and marketing	7,180			4,922			1,787
General and administrative	9,223			6,637			4,012
Total stock-based compensation	26,594			19,115			8,451
Tax benefit from stock-based compensation	(688		)	(1,535		)	(2,417		)
Total stock-based compensation, net of tax effect	$	25,906		$	17,580		$	6,034