Consolidated Statement of Stockholders' Equity (USD $)
In Thousands, unless otherwise specified
Total
Common Stock
Additional Paid-in Capital
Retained Earnings
Accumulated Other Comprehensive Gain/(Loss)
Treasury Stock
Balance at Dec. 31, 2011 $ 347,549 $ 590 $ 137,447 $ 345,078 $ (595) $ (134,971)
Balance, shares at Dec. 31, 2011   58,981        
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Stock-based compensation 13,729   13,729      
Exercise of stock options, shares, net   2,212        
Exercise of stock options 2,257 22 2,235      
Tax withholdings related to net exercise of stock options (10,418)   (10,418)      
Excess tax benefit of option exercises and restricted stock, net of tax shortfall 8,145   8,145      
Stock issued under employee stock purchase plan, shares   99        
Stock issued under employee stock purchase plan 1,340 1 1,339      
Stock issued under restricted stock plan, shares   33        
Stock issued under restricted stock plan, net of shares held for taxes (313)   (313)      
Exercise of warrants, shares   81        
Exercise of warrants 490 1 489      
Tax withholdings related to net exercise of warrants (944)   (944)      
Repurchase of common stock (602)         (602)
Net income 121,146     121,146    
Unrealized gains (losses) on investments, net of tax 817       817  
Balance at Dec. 31, 2012 483,196 614 151,709 466,224 222 (135,573)
Balance, shares at Dec. 31, 2012   61,406        
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Stock-based compensation 13,934   13,934      
Exercise of stock options, shares, net   590        
Exercise of stock options 10,464 6 10,458      
Tax withholdings related to net exercise of stock options (9,170)   (9,170)      
Excess tax benefit of option exercises and restricted stock, net of tax shortfall 1,516   1,516      
Stock issued under employee stock purchase plan, shares   116        
Stock issued under employee stock purchase plan 1,234 1 1,233      
Stock issued under restricted stock plan, shares   115        
Stock issued under restricted stock plan, net of shares held for taxes (1,080) 1 (1,081)      
Exercise of warrants, shares   104        
Exercise of warrants 231 1 230      
Repurchase of common stock (201,496)         (201,496)
Net income 45,883     45,883    
Unrealized gains (losses) on investments, net of tax (174)       (174)  
Balance at Dec. 31, 2013 344,538 623 168,829 512,107 48 (337,069)
Balance, shares at Dec. 31, 2013   62,331        
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Stock-based compensation 10,558   10,558      
Exercise of stock options, shares, net   388        
Exercise of stock options 3,108 4 3,104      
Excess tax benefit of option exercises and restricted stock, net of tax shortfall 326   326      
Stock issued under restricted stock plan, shares   238        
Stock issued under restricted stock plan, net of shares held for taxes (2,094) 3 (2,097)      
Net income 9,668     9,668    
Unrealized gains (losses) on investments, net of tax (223)       (223)  
Balance at Dec. 31, 2014 $ 365,881 $ 630 $ 180,720 $ 521,775 $ (175) $ (337,069)
Balance, shares at Dec. 31, 2014   62,957