Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation (Narrative) (Details)

v3.3.1.900
Stock-Based Compensation (Narrative) (Details) - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Shares authorized 20,800,000    
Shares available for future grants 3,462,454    
Tax benefit for the deduction from stock-based award transactions $ 11,872,000 $ 8,835,000 $ 4,793,000
Stock-based compensation expense 11,672,000 11,120,000 8,878,000
Stock Options [Member]      
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]      
Stock-based compensation expense 3,637,000 3,587,000 3,479,000
Unrecognized costs related to share based compensation $ 6,096,000    
Weighted average period of recognition of unrecognized costs related to stock options, years 2 years 18 days    
Intrinsic value of stock options exercised $ 20,400,000 16,345,000 7,491,000
Cash received on exercises of stock options $ 17,442,000 22,277,000 19,537,000
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 $ 8,035,000 $ 7,533,000 $ 5,399,000
Unrecognized costs related to share based compensation $ 12,925,000    
Weighted average period of recognition of unrecognized costs related to stock options, years 1 year 11 months 1 day    
Company withheld shares 90,355 78,265 83,366
Company withheld shares, tax obligations $ 4,895,000 $ 3,141,000 $ 2,291,000
Grant date fair value of vested units $ 6,848,000 $ 5,554,000 $ 5,362,000