Common Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	May 31, 2011	Dec. 31, 2013	Dec. 31, 2011
Common Stock Issuances
Number of shares of common stock issued in public offering	7,130,000
Issuance price per share (in dollars per share)	$ 7.25
Net proceeds from public offering	$ 49,333		$ 49,333
Underwriting discounts, commissions and offering costs	$ 2,360
Warrants
Number of shares that can be purchased by warrants issued		4,086
Exercise price of warrants issued to purchase shares of common stock (in dollars per share)		$ 3.30
Period of expiration of warrants from the lease term commencement date		10 years