Interim Financial Statements (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Public Offering [Abstract]
Proceeds	$ 37,455
Public Offering shares issued	8,750,000
Proceeds from future sales of common stock under an agreement with investment bank	50,000
Funding and Financial Matters [Abstract]
Cash and cash equivalents at end of period	94,036	55,284	65,860	58,838
Increase in cash and cash equivalents	$ 28,176	$ (3,554)
Minimum number of years cash will fund operations (in years)	1 year