Stockholder's Equity (Details) (USD $)	3 Months Ended		12 Months Ended						100 Months Ended		0 Months Ended		1 Months Ended		2 Months Ended	0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Mar. 31, 2014	Mar. 05, 2014	Mar. 05, 2014 June 2012 Controlled Equity Offering Sales Agreement	Jun. 21, 2012 June 2012 Controlled Equity Offering Sales Agreement	Mar. 31, 2014 June 2012 Controlled Equity Offering Sales Agreement	Mar. 31, 2014 June 2012 Controlled Equity Offering Sales Agreement	Feb. 27, 2014 June 2012 Controlled Equity Offering Sales Agreement	Mar. 05, 2014 June 2012 Controlled Equity Offering Sales Agreement Maximum
Stockholders' equity
Common stock sold by the entity (in shares)													228,249		3,644,143
Gross proceeds from sale of common stock by the entity	$ 22,606,000	$ 4,671,000							$ 233,774,000				$ 1,400,000		$ 21,200,000
Common stock, average selling price (in dollars per share)													$ 6.08		$ 5.82
Maximum share amount to be issued and sold under agreement												30,000,000
Common stock, par value (in dollars per share)	$ 0.0001		$ 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%
Selling agent fees	624,000		5,623,000	3,774,000	2,148,000	468,000	260,000	73,000						600,000
Proceeds from exercise of stock options	$ 36,000	$ 105,000							$ 155,000