Stockholders' Equity	3 Months Ended
Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Equity Incentive Plans As of March 31, 2018, the Company maintains two equity incentive plans, the 2002 Stock Plan and the 2010 Equity Incentive Award Plan (together, the “Plans”). These plans were approved by the stockholders and are described in the Company’s Annual Report on Form 10-K filed with the SEC on March 14, 2018. Currently, the Company only grants shares from the 2010 Equity Incentive Award Plan. To date, awards granted under the Plans consist of stock options, restricted stock units (“RSUs”) and performance restricted stock units (“PRSUs”). Stock Options During the three months ended March 31, 2018, 65,000 shares of stock options were granted with a grant date fair value of $6.20 per share. In August 2017, the Company granted 1.2 million shares of performance-based stock option awards to its executives. In February 2018, the Compensation Committee of the Company’s Board of Directors concluded that the performance target was not met and all such performance-based stock options were forfeited and canceled at that time. During the three months ended March 31, 2018, 1,420 shares of stock options were exercised at a weighted-average exercise price of $5.42 per share. As of March 31, 2018, unrecognized stock-based compensation expense of $3.7 million related to stock options, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 2.9 years. Restricted Stock Units During the three months ended March 31, 2018, 27,586 shares of RSUs were granted with a grant date fair value of $7.25 per share. During the three months ended March 31, 2018, 152,821 shares of RSUs vested. As of March 31, 2018, unrecognized stock-based compensation expense of $6.6 million related to RSUs, net of estimated forfeitures, was expected to be recognized over a weighted-average period of 1.6 years. Performance Restricted Stock Units During the three months ended March 31, 2018, 75,000 PRSUs vested. As of March 31, 2018, unrecognized stock-based compensation expense of $0.1 million related to PRSUs, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 0.9 years. Employee Stock Purchase Plans The Company’s Amended and Restated Employee Stock Purchase Plan (“ESPP”) allows employees to purchase shares of the Company’s common stock through payroll deductions of up to 15% of their annual compensation subject to certain Internal Revenue Code limitations. In addition, no participant may purchase more than 2,000 shares of common stock in each offering period. The offering periods under the ESPP are six-month periods commencing on May 15^th and November 15^th of each year. The price of common stock purchased under the ESPP is 85% of the lower of the fair market value of the common stock on the commencement date and the end date of each six-month offering period. As of March 31, 2018, there were 2.5 million shares available for issuance under the ESPP. During the three months ended March 31, 2018, no shares were purchased under the ESPP. As of March 31, 2018, unrecognized stock-based compensation expense of $0.2 million related to the ESPP is expected to be recognized over a remaining service period of 1.5 months. Under the 2017 Nonqualified Employee Stock Purchase Plan (“Nonqualified ESPP”), eligible employees can purchase shares of the Company’s common stock through payroll deductions of up to 25% of their annual compensation. Eligible employees have the right to (a) purchase the maximum number of whole shares of common stock that can be purchased with the elected payroll deductions during each offering period for which the employee is enrolled at a purchase price equal to the closing price of the Company’s common stock on the last day of such offering period and (b) receive an equal number of shares of the Company’s common stock that are subject to a risk of forfeiture in the event the employee terminates employment within the one year period immediately following the purchase date. The Nonqualified ESPP provides two six-month offering periods, from January 1 through June 30 and July 1 through December 31 of each year. The maximum number of shares of common stock currently authorized for issuance under the Nonqualified ESPP is 1,000,000 shares, with a maximum of 500,000 shares allocated per purchase period. As of March 31, 2018, there were 0.6 million shares available for issuance under the Nonqualified ESPP. As of March 31, 2018, unrecognized stock-based compensation expense of $1.8 million related to the Nonqualified ESPP is expected to be recognized over a remaining service period of 0.9 years.

Stockholders’ Equity

Equity Incentive Plans

As of March 31, 2018, the Company maintains two equity incentive plans, the 2002 Stock Plan and the 2010 Equity Incentive Award Plan (together, the “Plans”). These plans were approved by the stockholders and are described in the Company’s Annual Report on Form 10-K filed with the SEC on March 14, 2018. Currently, the Company only grants shares from the 2010 Equity Incentive Award Plan. To date, awards granted under the Plans consist of stock options, restricted stock units (“RSUs”) and performance restricted stock units (“PRSUs”).

Stock Options

During the three months ended March 31, 2018, 65,000 shares of stock options were granted with a grant date fair value of $6.20 per share.

In August 2017, the Company granted 1.2 million shares of performance-based stock option awards to its executives. In February 2018, the Compensation Committee of the Company’s Board of Directors concluded that the performance target was not met and all such performance-based stock options were forfeited and canceled at that time.

During the three months ended March 31, 2018, 1,420 shares of stock options were exercised at a weighted-average exercise price of $5.42 per share. As of March 31, 2018, unrecognized stock-based compensation expense of $3.7 million related to stock options, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 2.9 years.

Restricted Stock Units

During the three months ended March 31, 2018, 27,586 shares of RSUs were granted with a grant date fair value of $7.25 per share. During the three months ended March 31, 2018, 152,821 shares of RSUs vested. As of March 31, 2018, unrecognized stock-based compensation expense of $6.6 million related to RSUs, net of estimated forfeitures, was expected to be recognized over a weighted-average period of 1.6 years.

Performance Restricted Stock Units

During the three months ended March 31, 2018, 75,000 PRSUs vested. As of March 31, 2018, unrecognized stock-based compensation expense of $0.1 million related to PRSUs, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 0.9 years.

Employee Stock Purchase Plans

The Company’s Amended and Restated Employee Stock Purchase Plan (“ESPP”) allows employees to purchase shares of the Company’s common stock through payroll deductions of up to 15% of their annual compensation subject to certain Internal Revenue Code limitations. In addition, no participant may purchase more than 2,000 shares of common stock in each offering period.

The offering periods under the ESPP are six-month periods commencing on May 15^th and November 15^th of each year. The price of common stock purchased under the ESPP is 85% of the lower of the fair market value of the common stock on the commencement date and the end date of each six-month offering period. As of March 31, 2018, there were 2.5 million shares available for issuance under the ESPP. During the three months ended March 31, 2018, no shares were purchased under the ESPP. As of March 31, 2018, unrecognized stock-based compensation expense of $0.2 million related to the ESPP is expected to be recognized over a remaining service period of 1.5 months.

Under the 2017 Nonqualified Employee Stock Purchase Plan (“Nonqualified ESPP”), eligible employees can purchase shares of the Company’s common stock through payroll deductions of up to 25% of their annual compensation. Eligible employees have the right to (a) purchase the maximum number of whole shares of common stock that can be purchased with the elected payroll deductions during each offering period for which the employee is enrolled at a purchase price equal to the closing price of the Company’s common stock on the last day of such offering period and (b) receive an equal number of shares of the Company’s common stock that are subject to a risk of forfeiture in the event the employee terminates employment within the one year period immediately following the purchase date. The Nonqualified ESPP provides two six-month offering periods, from January 1 through June 30 and July 1 through December 31 of each year. The maximum number of shares of common stock currently authorized for issuance under the Nonqualified ESPP is 1,000,000 shares, with a maximum of 500,000 shares allocated per purchase period. As of March 31, 2018, there were 0.6 million shares available for issuance under the Nonqualified ESPP. As of March 31, 2018, unrecognized stock-based compensation expense of $1.8 million related to the Nonqualified ESPP is expected to be recognized over a remaining service period of 0.9 years.