Convertible Preferred Stock and Stock Warrants (Details) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended
	Feb. 07, 2014	Mar. 31, 2015	Mar. 31, 2014
Warrants and Rights Note Disclosure [Abstract]
Stock warrants exercised, shares	1,277,250
Warrants exercised, price per share (in dollars per share)	$ 1.21
Proceeds from exercise of stock warrants	$ 1,500	$ 0	$ 1,545