Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Details Textual)

v3.6.0.2
Stockholders' Equity (Details Textual) - USD ($)
1 Months Ended 12 Months Ended
May 31, 2012
May 29, 2009
May 31, 2016
Sep. 30, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Corporate Share Repurchase [Abstract]              
Shares repurchased in period (shares)         40,500 6,120 1,253,425
Shares repurchased in period, value         $ 3,901,000 $ 489,000 $ 67,955,000
Stock repurchase program, authorized amount       $ 200,000,000.0      
Stock repurchase program, period in force       3 years      
Stock repurchase program, remaining authorized repurchase amount         $ 195,600,000    
Stock Options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Weighted-average grant date fair value per share of stock options (in USD per share)         $ 46.53 $ 35.39 $ 46.20
Intrinsic value of options exercised         $ 12,000,000 $ 20,700,000 $ 15,300,000
Unrecognized compensation cost         $ 17,500,000    
Weighted-average period in which cost is expected to be recognized         2 years 2 months 20 days    
Cash received from options exercised         $ 6,200,000 $ 8,700,000 $ 4,400,000
Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Weighted-average period in which cost is expected to be recognized         1 year 1 month 20 days    
Unrecognized compensation cost, restricted stock         $ 13,800,000    
2002 Stock Incentive Plan | Stock Options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Increase the number of shares under the 2002 Stock Incentive Plan (shares) 1,800,000 1,300,000 900,000        
Shares available for future option grants (shares)         1,000,000    
Amended ESPP              
Employee Stock Purchase Plan [Abstract]              
Shares allowed to purchase in employee stock purchase plan (shares)         1,250    
Percentage lesser of fair market value taken as purchase price of share         85.00%    
Common stock issued under amended ESSP (shares)         1,961 3,374 3,774