Annual report pursuant to Section 13 and 15(d)

Compensation and Other Benefit Plans - Additional Information (Details)

v3.6.0.2
Compensation and Other Benefit Plans - Additional Information (Details) - USD ($)
 1 Months Ended 12 Months Ended
Feb. 28, 2017
May 31, 2016
May 31, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Deferred savings plan [Abstract]            
Maximum annual contribution per employee (in hundredths)       50.00%    
Maximum annual contribution per employee       $ 18,000 $ 18,000 $ 17,500
Maximum annual contribution per employee over 50 years old       $ 24,000 $ 24,000 $ 23,000
Age requirement for participant to be eligible for a catch-up contribution, minimum       50 years 50 years 50 years
Employer matching contribution percentage, maximum (in hundredths)       50.00%    
Deferred savings plan expense       $ 500,000 $ 800,000 $ 1,000,000
Deferred savings plan expense paid in common shares (in hundredths)       100.00% 100.00% 100.00%
Number of shares of common stock to be issued upon exercise of options and RSUs outstanding (in shares)       671,493    
Non Executive Employee [Member]            
Deferred savings plan [Abstract]            
Vesting period       4 years    
Directors [Member]            
Deferred savings plan [Abstract]            
Vesting period       1 year    
Stock Options [Member]            
Deferred savings plan [Abstract]            
Granted, shares       234,962 89,844 94,487
Additional disclosures [Abstract]            
Minimum age required for employees to qualify for immediate vesting of RSUs       55 years    
Threshold years required for retirement age       70 years    
Options exercised, aggregate intrinsic value         $ 400,000 $ 2,900,000
Stock options exercised       0 8,177 45,737
Options outstanding, aggregate intrinsic value       $ 0    
Options outstanding, weighted average remaining contractual term       6 years 11 months 5 days    
Options exercisable, aggregate intrinsic value       $ 0    
Options exercisable, weighted average remaining contractual term       5 years 22 days    
Unrecognized compensation expense related to stock options       $ 2,400,000    
Weighted average period of unrecognized compensation expense expected to be recognized       1 year 1 month 6 days    
Stock options vested and expected to vest [Abstract]            
Options vested and expected to vest, number of shares (in shares)       544,021    
Options vested and expected to vest, weighted-average exercise price (in dollars per share)       $ 80.52    
Stock option activity [Roll Forward]            
Exercisable at end of year (in shares)       315,384 280,149 245,346
Stock Options [Member] | Non Executive Employee [Member] | Vesting within One Year [Member]            
Deferred savings plan [Abstract]            
Vesting period       1 year    
Granted, shares       207,100    
Restricted Stock Units (RSUs) [Member]            
Additional disclosures [Abstract]            
Minimum age required for employees to qualify for immediate vesting of RSUs       55 years    
Threshold years required for retirement age       70 years    
Weighted average period of unrecognized compensation expense expected to be recognized       7 months 6 days    
Unrecognized compensation expense related to employee RSUs       $ 1,400,000    
Stock option activity [Roll Forward]            
Granted, shares       127,367    
Unvested RSU activity, weighted average grant date fair value [Roll Forward]            
Total grant-date fair value of RSUs, vested       $ 5,300,000 $ 5,500,000 $ 3,900,000
Unvested balance end of period (in shares)       91,228 106,205  
Forfeited upon termination, (in shares)       33,695    
Restricted Stock Units (RSUs) [Member] | 2016 Restructuring [Member] | Subsequent Event [Member]            
Unvested RSU activity, weighted average grant date fair value [Roll Forward]            
Forfeited upon termination, (in shares) 12,419          
Restricted Stock Units (RSUs) [Member] | Vesting within One Year [Member]            
Stock option activity [Roll Forward]            
Granted, shares       114,517    
Restricted Stock Units (RSUs) [Member] | Non Executive Employee [Member]            
Deferred savings plan [Abstract]            
Vesting period       3 years    
Restricted Stock Units (RSUs) [Member] | Non Executive Employee [Member] | Vesting within One Year [Member]            
Deferred savings plan [Abstract]            
Vesting period       1 year    
Restricted Stock Units (RSUs) [Member] | Directors [Member]            
Deferred savings plan [Abstract]            
Vesting period       1 year    
2015 ESPP [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Percentage related to employees to purchase shares at the lower fair market value at offering period       85.00%    
Common stock reserved for future issuance (in shares)       15,000    
Percentage of compensation of eligible employees to purchase shares of entity common stock at discount through payroll deductions       10.00%    
1998 ESPP [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Percentage related to employees to purchase shares at the lower fair market value at offering period       95.00%    
Shares authorized for issuance       233,333    
1998 ESPP [Member] | Maximum [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Employee compensation available for share purchases, maximum (in hundredths)       15.00%    
1998 and 2015 Employee Stock Purchase Plan [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Shares purchased (in shares)       7,070 6,029 885
Net payroll deductions to acquire shares       $ 60,000 $ 170,000 $ 74,000
2010 Plan [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Shares authorized for issuance   1,108,560        
Deferred savings plan [Abstract]            
Increase in aggregate number of shares authorized for issuance   170,000        
Expiration period       ten years from the date of the grant or three to six months from the date of termination of employment (longer in case of death or certain retirements).    
2010 Plan [Member] | Subsequent Event [Member]            
Deferred savings plan [Abstract]            
Granted, shares 1,018,000          
2010 Plan [Member] | Stock Options [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Shares authorized for issuance     938,560      
Deferred savings plan [Abstract]            
Increase in aggregate number of shares authorized for issuance     267,500      
Reducing shares from number of available shares (in shares)     1.18      
Long Term Incentive Plan [Member]            
Deferred savings plan [Abstract]            
Shares available for grant       94,815