Goodwill (Tables)
 9 Months Ended
Sep. 30, 2012
Goodwill [Abstract]  
Changes in the Company’s goodwill balance
The following table presents the changes in the Company’s goodwill balance:

Balance at December 31, 2010
$
224,920

Goodwill arising from acquisitions
31,140

Balance at December 31, 2011
256,060

Other
(23
)
Balance at September 30, 2012
$
256,037