Stockholders' Equity (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013 2012 Equity Incentive Plan
Stock-Based Compensation Plans
Vesting period		4 years
Vesting period expiration		10 years
Options
Outstanding at the beginning of the period (in shares)	1,820,784
Granted (in shares)	876,500
Exercised (in shares)	(50,304)
Canceled (in shares)	(98,666)
Outstanding at the end of the period (in shares)	2,548,314
Weighted-Average Exercise Price (Per Share)
Outstanding at the beginning of the period (in dollars per share)	$ 4.46
Granted (in dollars per share)	$ 5.37
Exercised (in dollars per share)	$ 1.18
Canceled (in dollars per share)	$ 6.35
Outstanding at the end of the period (in dollars per share)	$ 4.77
Weighted-average fair value of options granted during the period	$ 3.45