Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation (Narrative) (Details)

v3.6.0.2
Stock-Based Compensation (Narrative) (Details) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Shares authorized 20,800,000    
Shares available for future grants 3,089,699    
Tax benefit for the deduction from stock-based award transactions $ 9,576,000 $ 11,872,000 $ 8,835,000
Stock-based compensation expense 10,986,000 11,672,000 11,120,000
Stock Options [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Stock-based compensation expense 3,896,000 3,637,000 3,587,000
Unrecognized costs related to share based compensation $ 6,678,000    
Weighted average period of recognition of unrecognized costs related to stock options, years 2 years 1 month 9 days    
Intrinsic value of stock options exercised $ 12,976,000 20,400,000 16,345,000
Cash received on exercises of stock options $ 13,167,000 17,442,000 22,277,000
Stock Options [Member] | After2008 [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Vesting period of options granted, years 4 years    
Expiration period, years 10 years    
Service Based Restricted Stock Units [Member] | After2008 [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Vesting period of options granted, years 4 years    
Performance Based Restricted Stock Units [Member] | Prior To2010 [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Additional requisite service period, years 1 year    
Performance Based Restricted Stock Units [Member] | Minimum [Member] | Prior To2010 [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Vesting period of options granted, years 2 years 6 months    
Performance Based Restricted Stock Units [Member] | Minimum [Member] | After2009 [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Vesting period of options granted, years 2 years    
Performance Based Restricted Stock Units [Member] | Maximum [Member] | Prior To2010 [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Vesting period of options granted, years 3 years    
Performance Based Restricted Stock Units [Member] | Maximum [Member] | After2009 [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Vesting period of options granted, years 3 years    
Restricted Stock Units (RSUs) [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Stock-based compensation expense $ 7,090,000 $ 8,035,000 $ 7,533,000
Unrecognized costs related to share based compensation $ 12,430,000    
Weighted average period of recognition of unrecognized costs related to stock options, years 1 year 11 months 10 days    
Company withheld shares 88,335 90,355 78,265
Company withheld shares, tax obligations $ 5,127,000 $ 4,895,000 $ 3,141,000
Grant date fair value of vested units $ 7,988,000 $ 6,848,000 $ 5,554,000