Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Summary of Equity Incentive Plan Activity

Equity incentive plan activity under the 2000 Plan and the 2009 Plan is summarized as follows:

Equity Incentive Plan Activity	Shares Available for Grant
Balance at December 31, 2014	2,708,524
Authorized	3,141,509
Granted	(1,569,865	)
Forfeited	674,786
Expired	1,250
Shares withheld for taxes and not issued	35,379
Balance at December 31, 2015	4,991,583

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 year ended December 31, 2015:

Stock Options Activity	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2014	6,892,810		$	6.13	8.22	$	173,338
Granted	312,200		31.66
Exercised	(2,112,131	)	3.44
Forfeited	(645,480	)	7.84
Expired	(1,250	)	10.98
Balance at December 31, 2015	4,446,149		$	8.96	7.56	$	52,108
Exercisable at December 31, 2015	2,100,591		$	6.20	7.16	$	28,922
Vested and expected to vest at December 31, 2015	4,257,065		$	8.70	7.53	$	50,675

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 year ended December 31, 2015:

Restricted Stock Unit Activity	Number of Units		Weighted-Average Grant Date Fair Value
Nonvested at December 31, 2014	7,750		$	13.21
Granted	1,084,379		28.73
Vested	(106,136	)	32.83
Forfeited	(29,306	)	32.70
Nonvested at December 31, 2015	956,687		$	28.03

Summary of Performance Based Restricted Stock Unit Activity

The following table summarizes PSU activity under the Company’s equity-based plans for the year ended December 31, 2015:

Performance Based Restricted Stock Unit Activity	Number of Units	Weighted-Average Grant Date Fair Value
Outstanding units at December 31, 2014	—	$	—
Granted	173,286	33.51
Units converted	—	—
Forfeited	—	—
Outstanding units at December 31, 2015	173,286	$	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	Year Ended December 31,
	2015		2014		2013
Expected term (in years)	6.08		6.05		6.04
Expected volatility	39	%	58	%	48	%
Risk-free interest rate	1.73	%	1.80	%	1.26	%
Expected dividend yield	0	%	0	%	0	%

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

ESPP Assumptions	Year Ended December 31,
	2015		2014		2013
Expected term (in years)	0.50		0.50		n/a
Expected volatility	34-76%		33-58%		n/a
Risk-free interest rate	0.07-0.33%		0.06-0.07%		n/a
Expected dividend yield	0	%	0	%	n/a

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): 

	Year Ended December 31,
	2015		2014		2013
Cost of providing services	$	4,244	$	2,658	$	1,193
Sales and marketing	4,490		2,755		1,284
General and administrative	7,501		4,517		3,220
Systems development and programming costs	1,688		1,030		416
	$	17,923	$	10,960	$	6,113

Schedule of Earnings Per Share

The following table sets forth the computation of the Company’s basic and diluted net income per share attributable to common stock (in thousands, except per share data):

	Year Ended December 31,
	2015		2014			2013
Numerator (basic)
Net income	$	31,695	$	15,497		$	13,147
Less net income allocated to participating securities	—		(2,224		)	(9,926		)
Net income attributable to common stock	$	31,695	$	13,273		$	3,221
Denominator (basic)
Weighted average shares of common stock outstanding	70,228		56,161			12,353
Basic EPS	$	0.45	$	0.24		$	0.26
Numerator (diluted)
Net income	$	31,695	$	15,497		$	13,147
Less net income allocated to participating securities	—		(2,114		)	(9,303		)
Net income attributable to common stock	$	31,695	$	13,383		$	3,844
Denominator (diluted)
Weighted average shares of common stock	70,228		56,161			12,353
Dilutive effect of stock options and restricted stock units	2,390		3,406			3,379
Weighted average shares of common stock outstanding	72,618		59,567			15,732
Diluted EPS	$	0.44	$	0.22		$	0.24
Common stock equivalents excluded from income per diluted    share because of their anti-dilutive effect	1,004		526			1,389