Inventories (Tables)
 12 Months Ended
Dec. 31, 2013
Inventory Disclosure [Abstract]  
Components of inventory
The components of inventories consist of the following (in thousands):
 
December 31,
 
2012
 
2013
Purchased parts and materials
$
3,051

 
$
2,911

Finished goods
1,986

 
3,628

Total inventory
$
5,037

 
$
6,539