Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2016

Equity [Abstract]

Summary of Equity Incentive Plan Activity

Equity incentive plan activity for the nine months ended September 30, 2016 is summarized as follows:

Equity Incentive Plan Activity	Shares Available for Grant
Balance at December 31, 2015	4,991,583
Authorized	3,166,714
Granted	(2,195,407	)
Forfeited	400,766
Expired	65,626
Shares withheld for taxes and not issued	151,826
Balance at September 30, 2016	6,581,108

Summary of Stock Option Activity under the Company's Equity-Based Plans

The following table summarizes stock option activity under the Company’s equity-based plans for the nine months ended September 30, 2016:

Stock Option Activity	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2015	4,446,149		$	8.96	7.56	$	52,108
Exercised	(931,330	)	3.85
Forfeited	(231,625	)	18.45
Expired	(65,626	)	28.59
Balance at September 30, 2016	3,217,568		$	9.35	6.88	$	42,872
Exercisable at September 30, 2016	2,126,351		$	7.33	6.61	$	31,741
Vested and expected to vest at September 30, 2016	3,160,624		$	9.21	6.86	$	42,442

Summary of Restricted Stock Unit Activity under the Company's Equity-Based Plans

The following table summarizes RSU activity under the Company’s equity-based plans for the nine months ended September 30, 2016:

Restricted Stock Unit Activity	Number of Units		Weighted Average Grant Date Fair Value
Nonvested at December 31, 2015	956,687		$	28.03
Granted	2,195,407		$	18.09
Vested	(511,210	)	$	24.13
Forfeited	(145,267	)	$	22.95
Nonvested at September 30, 2016	2,495,617		$	20.37

Summary of Performance Based Restricted Stock Unit Activity

The following table summarizes PSU activity under the Company’s equity-based plans for the nine months ended September 30, 2016:

Performance Based Restricted Stock Unit Activity	Number of Units		Weighted Average Grant Date Fair Value
Outstanding units at December 31, 2015	173,286		$	33.51
Granted	—		$	—
Units converted	—		$	—
Forfeited	(23,874	)	$	33.51
Outstanding units at September 30, 2016	149,412		$	33.51

Summary of Significant Assumptions Used to Estimate Fair Value of Stock Options under Black-Scholes Model

The fair value of stock-based awards is estimated on the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions:

Stock Option Assumptions	Three Months Ended September 30,			Nine Months Ended September 30,
	2016	2015		2016	2015
Expected term (in years)	N/A	6.11		N/A	6.08-6.11
Expected volatility	N/A	46	%	N/A	39-46%
Risk-free interest rate	N/A	1.62	%	N/A	1.62-1.96%
Expected dividend yield	N/A	0	%	N/A	0	%

Summary of Significant Assumptions Used to Estimate Fair Value of Employee Stock Purchase Plans under Black-Scholes Model

ESPP Assumptions	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Expected term (in years)	0.50		0.50		0.50		0.50
Expected volatility	43	%	43	%	43-76%		34-43%
Risk-free interest rate	0.38	%	0.08	%	0.33-0.38%		0.07-0.08%
Expected dividend yield	0	%	0	%	0	%	0	%

Summary of Stock-based Compensation Expense

Stock-based compensation expense for stock-based awards made to the Company’s employees pursuant to the equity plans was as follows (in thousands): 

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Cost of providing services	$	1,605	$	1,079	$	5,044	$	3,051
Sales and marketing	1,491		1,029		5,119		3,255
General and administrative	2,544		1,633		8,161		5,497
Systems development and programming costs	624		447		1,845		1,188
	$	6,264	$	4,188	$	20,169	$	12,991