Stockholders' Equity (Details 2) (USD $)	1 Months Ended	12 Months Ended
	Jan. 31, 2011	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 28, 2010
Stock-Based Compensation Plans
Vesting period		4 years
Vesting period expiration		10 years
Number of Shares
Balance at the beginning of the period (in shares)		1,820,784
Options granted (in shares)		1,298,500
Options forfeited (in shares)		(258,969)
Options expired (in shares)		(126,123)
Options exercised (in shares)		(56,418)
Balance at the end of the period (in shares)		2,677,774	1,820,784
Weighted-Average Exercise Price (Per Share)
Balance at the beginning of the period (in dollars per share)		$ 4.46
Options granted (in dollars per share)		$ 4.24
Options forfeited (in dollars per share)		$ 5.81
Options expired (in dollars per share)		$ 5.49
Options exercised (in dollars per share)		$ 1.17
Balance at the ending of the period (in dollars per share)		$ 4.24	$ 4.46
Warrants to purchase common stock		88,545
Total common stock reserved for future issuance		3,985,244
Number of shares authorized to be issued under the plan	141,795				153,026
Equity Incentive Plan period		10 years
Awards, common stock vested	56,998
Stock-based compensation expense		$ 2,013,000	$ 1,440,000	$ 821,000
Total fair value of options vested		3,200,000	1,600,000	97,000
Total intrinsic value of stock options exercised		187,000	787,000	607,000
Weighted-average fair value of options granted during the period		$ 2.73	$ 3.03	$ 6.98
Two Thousand One Stock Option Plan [Member]
Weighted-Average Exercise Price (Per Share)
Warrants to purchase common stock		555,774
Two Thousand One Stock Option Plan [Member] | Maximum [Member]
Weighted-Average Exercise Price (Per Share)
Number of shares authorized to be issued under the plan		3,408,247
Fair market value percentage of ordinary shares		85.00%
Equity Incentive Plan Twenty Twelve [Member]
Stock-Based Compensation Plans
Vesting period		4 years
Vesting period expiration		10 years
Weighted-Average Exercise Price (Per Share)
Warrants to purchase common stock		2,122,000
Shares available for future grant		1,218,925
Number of shares authorized to be issued under the plan, before 2001 Plan additions		1,123,131
Carryover of shares from 2001 Plan		1,066,975
Percentage of increase in the number of shares reserved for issuance		5.00%
Increase in the number of shares reserved for issuance		842,348
Fiscal year over which number of shares reserved for issuance will increase, starting year		2013
Fiscal year over which number of shares reserved for issuance will increase, ending year		2022
Employee Stock Purchase Plan Twenty Twelve [Member]
Stock-Based Compensation Plans
Look-back period for payroll deductions to acquire ownership interest		6 months
Weighted-Average Exercise Price (Per Share)
Number of shares authorized to be issued under the plan		168,469
Fair market value percentage of ordinary shares		85.00%
Stock Awards [Member]
Weighted-Average Exercise Price (Per Share)
Stock-based compensation expense				$ 401,000