Property and Equipment - Net (Details) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2013
Dec. 31, 2012
Schedule of property and equipment    
Property and equipment-gross $ 28,996 $ 23,526
Less accumulated depreciation (15,752) [1] (12,483) [1]
Total property and equipment-net 13,244 11,043
Computer equipment [Member]
   
Schedule of property and equipment    
Property and equipment-gross 18,829 [2] 17,630 [2]
Computer software [Member]
   
Schedule of property and equipment    
Property and equipment-gross 4,575 3,715
Furniture and fixtures [Member]
   
Schedule of property and equipment    
Property and equipment-gross 1,520 1,050
Leasehold improvements [Member]
   
Schedule of property and equipment    
Property and equipment-gross 968 732
Work in process [Member]
   
Schedule of property and equipment    
Property and equipment-gross 2,931 [3] 226 [3]
Other [Member]
   
Schedule of property and equipment    
Property and equipment-gross $ 173 $ 173
[1] Includes $1,834 and $1,798 of accumulated depreciation of equipment under capital leases as of December 31, 2012 and September 30, 2013, respectively.
[2] Includes equipment under capital lease obligations of approximately $5,882 and $4,988 as of December 31, 2012 and September 30, 2013, respectively.
[3] Includes internal-use software development costs of $40 and $2,800 as of December 31, 2012 and September 30, 2013, respectively.