Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

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

Compensation Expense Related to Stock-Based Compensation Plans

tock-based compensation expense related to stock options, RSUs and PSUs was as follows (in thousands):

	Year ended December 31,
	2015		2014		2013
Cost of sales	$	581	$	609	$	815
Research and development	734		1,062		1,912
Sales and marketing	1,554		1,059		821
General and administrative	4,550		3,994		5,223
	$	7,419	$	6,724	$	8,771

Estimated Fair Value of Each Stock Option Award

The estimated fair value of each stock option was determined on the date of grant using the Black-Scholes option valuation model with the following weighted-average assumptions for the option grants:

	Year ended December 31,
	2015		2014		2013
Risk-free interest rate	1.50	%	1.59	%	0.86	%
Expected option life (in years)	6.24		5.78		5.53
Volatility rate	40	%	42	%	44	%
Dividend rate	—	%	—	%	—	%

Summary of Status of Stock Option Activity

A summary of the status of stock option activity for the years ended December 31, 2013, 2014 and 2015 is as follows (in thousands, except price data and years):

	Number of Shares		Weighted- average exercise price per share		Weighted- average remaining contractual term (in years)	Aggregate intrinsic value
Outstanding at January 1, 2013	3,600		$	13.15
Granted	529		22.36
Exercised	(642	)	12.16
Cancelled	(13	)	10.61
Outstanding at December 31, 2013	3,474		14.74
Granted	559		26.63
Exercised	(251	)	13.67
Cancelled	(175	)	20.63
Outstanding at December 31, 2014	3,607		16.37
Granted	659		23.15
Exercised	(168	)	12.30
Cancelled	(131	)	23.41
Outstanding at December 31, 2015	3,967		$	17.44	5.54	$	19,225
Vested and expected to vest at December 31, 2015	3,827		$	17.20	5.52	$	19,192
Exercisable at December 31, 2015	2,657		$	14.37	4.16	$	18,503
Available for future grant at December 31, 2015	1,434

Summary of Status of Stock Awards Activity

A summary of the status of stock awards activity for the years ended December 31, 2013, 2014 and 2015 is as follows (in thousands, except price data):

	Shares		Weighted-average grant date fair value
Non-vested at January 1, 2013	522		$	13.87
Granted	74		23.53
Vested	(141	)	23.43
Forfeited	(1	)	15.26
Non-vested at December 31, 2013	454		16.22
Granted	145		25.73
Vested	(174	)	28.27
Forfeited	(23	)	18.19
Non-vested at December 31, 2014	402		14.84
Granted	171		22.79
Vested	(96	)	18.01
Forfeited	(18	)	22.87
Non-vested at December 31, 2015	459		$	21.61