Stock-Based Compensation (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Stock-based compensation      
Stock-based compensation expense $ 10,395,000 $ 13,655,000 $ 12,283,000
Stock-based compensation related to acquisition 0 0 42,000
Actek, Inc.
     
Stock-based compensation      
Stock-based compensation related to acquisition 0 0 42,000
Options
     
Stock-based compensation      
Stock-based compensation expense 866,000 838,000 1,171,000
Unrecognized compensation expense, stock options 2,600,000    
Weighted average recognition period 3 years 4 months 2 days    
Restricted Stock Units
     
Stock-based compensation      
Unrecognized compensation expense, share-based awards other than options 5,800,000    
Weighted average recognition period 1 year 4 months 7 days    
Performance Awards
     
Stock-based compensation      
Stock-based compensation expense 1,097,000 444,000 665,000
Non-performance Awards
     
Stock-based compensation      
Stock-based compensation expense 7,835,000 11,571,000 10,173,000
ESPP
     
Stock-based compensation      
Stock-based compensation expense 597,000 802,000 232,000
Unrecognized compensation expense, share-based awards other than options $ 300,000    
Weighted average recognition period 0 years 7 months 6 days