Stockholders' Equity

6 Months Ended

Jun. 30, 2015

Equity [Abstract]

Stockholders' Equity

Stockholders’ Equity

Issuances and Repurchases of Common Stock

During the six months ended June 30, 2015, 53,003 shares of common stock were issued in conjunction with the vesting and release of restricted stock units, 27,931 shares of common stock were issued due to the exercise of stock options and 25,080 shares of common stock were issued in connection with the Company’s employee stock purchase plan (the “ESPP”), resulting in net proceeds to the Company of approximately $0.8 million. During the six months ended June 30, 2015, 632,150 shares of outstanding common stock were repurchased under the Company’s previously announced share repurchase program for approximately $14.4 million. Additionally, 15,811 shares of outstanding common stock were repurchased in connection with payment of minimum tax withholding obligations for certain employees relating to the lapse of restrictions on certain restricted stock units for approximately $0.4 million. As of June 30, 2015, there was $35.6 million available under the Company’s share repurchase program.

Stock-Based Compensation

The compensation expense related to the Company’s stock-based compensation plans included in the accompanying Consolidated Statements of Operations was as follows (in thousands):

	Three months ended June 30,				Six months ended June 30,
	2015		2014		2015		2014
Cost of sales	$	104	$	95	$	341	$	328
Research and development	277		149		294		565
Sales and marketing	375		190		877		480
General and administrative	1,170		808		2,482		2,106
Total stock-based compensation expense	$	1,926	$	1,242	$	3,994	$	3,479

Total compensation expense recognized for the three months and six months ended June 30, 2015 includes $1.0 million and $2.4 million related to stock options and $0.9 million and $1.6 million related to restricted stock units, respectively. Total compensation expense recognized for the three and six months ended June 30, 2014 includes $1.0 million and $2.4 million related to stock options and $0.3 million and $1.1 million related to restricted stock units, respectively. As of June 30, 2015, total unrecognized compensation expense related to non-vested stock options was $8.6 million, which is expected to be recognized over a weighted-average period of approximately 2.6 years. As of June 30, 2015, total unrecognized compensation expense related to non-vested restricted stock units was $3.3 million, which is expected to be recognized over a weighted-average period of approximately 2.9 years. Compensation expense capitalized to inventory and compensation expense related to the Company’s ESPP were not material for the three and six months ended June 30, 2015 and 2014.

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

	Six months ended June 30,
	2015		2014
Risk-free interest rate	1.47	%	1.58	%
Expected option life (in years)	6.23		5.77
Volatility rate	40	%	42	%
Dividend rate	—	%	—	%

The weighted-average fair value of stock options granted during the six months ended June 30, 2015 and 2014 was $9.61 and $10.96, respectively. The Company granted 615,183 and 535,128 stock options during the six months ended June 30, 2015 and 2014, respectively. The weighted-average fair value of restricted stock units granted during the six months ended June 30, 2015 and 2014 was $23.58 and $25.46, respectively. The Company granted 137,214 and 108,030 shares of restricted stock units during the six months ended June 30, 2015 and 2014, respectively. The fair value of restricted stock units is determined based on the closing market price of the Company’s common stock on the grant date.