Property and Equipment - Net - Additional Disclosures (Details) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2013
Dec. 31, 2012
Property and Equipment - Net (Textual) [Abstract]    
Property and equipment-gross $ 28,996 $ 23,526
Accumulated depreciation of equipment under capital leases 15,752 [1] 12,483 [1]
Capital lease obligations [Member]
   
Property and Equipment - Net (Textual) [Abstract]    
Accumulated depreciation of equipment under capital leases 1,798 1,834
Computer equipment [Member]
   
Property and Equipment - Net (Textual) [Abstract]    
Property and equipment-gross 18,829 [2] 17,630 [2]
Computer equipment [Member] | Capital lease obligations [Member]
   
Property and Equipment - Net (Textual) [Abstract]    
Property and equipment-gross 4,988 5,882
Work in process [Member]
   
Property and Equipment - Net (Textual) [Abstract]    
Property and equipment-gross 2,931 [3] 226 [3]
Software Development [Member]
   
Property and Equipment - Net (Textual) [Abstract]    
Property and equipment-gross $ 2,800 $ 40
[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.