Stock-based Compensation (Tables)

The fair value of stock options granted was estimated at the date of grant using the following weighted-average assumptions:


	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Expected life in years		5.7			6.1			6.0			6.2
Risk-free interest rate		1.44	%		1.81	%		1.53	%		1.82	%
Volatility		45	%		46	%		45	%		48	%
Dividend yield		—			—			—			—
Weighted-average fair value of stock options granted	$	2.64		$	3.28		$	2.66		$	3.66

The following is a summary of the status of the Company’s stock options as of June 30, 2016 and the stock option activity during the six months ended June 30, 2016.


	Number of Shares			Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (In Years)		Aggregate Intrinsic Value (1)
Outstanding at December 31, 2015		4,622,886		$	6.63
Granted		172,802			5.99
Exercised		(83,048	)		2.26			$	363
Canceled		(332,484	)		8.74

Outstanding at June 30, 2016		4,380,156		$	6.53		6.55	$	12,036

Exercisable at June 30, 2016		2,303,494		$	6.12		4.62	$	7,711

Vested or expected to vest at June 30, 2016 (2)		3,908,182		$	6.50		6.27	$	10,993

(1)	The aggregate intrinsic value was calculated based on the positive difference between the fair value of the Company’s common stock on June 30, 2016 of $8.80 per share, or the date of exercise, as appropriate, and the exercise price of the underlying options.

(2)	This represents the number of vested options as of June 30, 2016 plus the number of unvested options expected to vest as of June 30, 2016 based on the unvested options outstanding at June 30, 2016 adjusted for an estimated forfeiture rate.

The following table summarizes the restricted stock unit activity during the six months ended June 30, 2016:


	Shares			Weighted Average Grant Date Fair Value
Unvested by December 31, 2015		1,503,814		$	6.69
Granted		243,922			5.95
Vested and issued		(100,720	)		8.75
Canceled		(153,276	)		7.73

Unvested by June 30, 2016		1,493,740		$	5.75