Stockholders' Equity (Details) (USD $)	6 Months Ended				0 Months Ended	2 Months Ended	4 Months Ended	6 Months Ended	0 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Mar. 05, 2014	Dec. 31, 2013	Mar. 05, 2014 June 2012 Controlled Equity Offering Sales Agreement	Mar. 04, 2014 June 2012 Controlled Equity Offering Sales Agreement	Jun. 30, 2014 June 2012 Controlled Equity Offering Sales Agreement	Jun. 30, 2014 June 2012 Controlled Equity Offering Sales Agreement	Mar. 05, 2014 June 2012 Controlled Equity Offering Sales Agreement Maximum
Stockholders' equity
Common stock, par value (in dollars per share)	$ 0.0001		$ 0.0001	$ 0.0001
Additional aggregate offering price of common stock					$ 50,000,000
Commission payable to Cantor as a percentage of gross sales price per share sold									3.00%
Common stock sold by the entity (in shares)						3,644,143	273,006
Gross proceeds from sale of common stock by the entity	22,795,000	94,734,000				21,200,000	1,578,260
Common stock, average selling price (in dollars per share)						$ 5.82	$ 5.78
Maximum share amount to be issued and sold under agreement						30,000,000
Selling agent fees	629,000							629,000
Proceeds from exercise of stock options	$ 36,000	$ 119,000