Intangible Assets (Details 2) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2013
Dec. 31, 2012
Expected annual amortization expense related to amortizable intangible assets    
Nine months ending December 31, 2013 $ 6,096  
2014 7,834  
2015 7,493  
2016 6,659  
2017 6,276  
2018 6,105  
Thereafter 32,998  
Net Book Value/Total expected amortization expense $ 73,461 $ 67,768