Property and Equipment - Credit Facility with SVB (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
May 31, 2013
Line of Credit Facility [Line Items]        
Line of Credit Facility, Maximum Borrowing Capacity       $ 26,500,000
Impairment of long-lived assets $ 0 $ 949,000 $ 0