Property and Equipment (Tables)
 12 Months Ended
Dec. 31, 2013
Property, Plant and Equipment [Abstract]  
Schedule of property and equipment
Property and equipment consist of the following (in thousands):
 
As of
 
As of
 
December 31, 2013
 
December 31, 2012
Lab equipment and machinery
$
49,264

 
$
38,667

Leasehold improvements
4,413

 
2,873

Computer equipment and software
3,563

 
3,467

Furniture and fixtures
182

 
160

Construction in progress
6,544

 
5,964

Total property and equipment
63,966

 
51,131

Less accumulated depreciation
(35,481
)
 
(27,073
)
Property and equipment, net
$
28,485

 
$
24,058
Schedule of depreciation expense
The following table presents depreciation expense included in the Consolidated Statement of Operations and includes amortization of leasehold improvements (in thousands): 
 
Years Ended December 31,
 
2013
 
2012
 
2011
Depreciation expense
$
8,781

 
$
7,411

 
$
6,992