Equity Incentive Plans

6 Months Ended

Jun. 30, 2016

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

Equity Incentive Plans

9. Equity Incentive Plans

Stock Options

During the six months ended June 30, 2016, the Company had the following option activities under its equity incentive plans:

				Outstanding Options
	Available for Grant			Shares			Weighted Average Exercise Price		Weighted  Average Remaining Contractual Term		Aggregate Intrinsic Value
Balance at December 31, 2015		2,157,641			7,847,449		$	8.52
Shares authorized		1,750,000
Granted (1)		(2,033,410	)		1,706,600			3.42
Exercised		—			(107,500	)		2.05
Forfeited and expired		114,225			(114,225	)		7.51
Balance at June 30, 2016		1,988,456			9,332,324		$	7.68		6.95	$	1,853,141

(1) The difference between shares granted in the number of shares available for grant and outstanding options represents the RSUs granted for the period.

Stock-based Compensation

Total stock-based compensation expense was $2.3 million and $4.6 million during the three and six months ended June 30, 2016, respectively, and $2.4 million and $4.8 million, respectively, during the same period ended June 30, 2015. As of June 30, 2016, $11.8 million, $1.1 million, and $0.1 million of total unrecognized compensation expenses associated with outstanding stock options, unvested RSUs, and the ESPP, net of estimated forfeitures, were expected to be recognized over a weighted-average period of 2.57, 2.01, and 0.38 years, respectively.