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Equity Incentive Plans and Stock-Based Compensation (Details 5)
1 Months Ended 3 Months Ended 12 Months Ended
Apr. 23, 2015
shares
Apr. 24, 2014
shares
Sep. 27, 2013
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Apr. 30, 2012
shares
Apr. 30, 2009
shares
Sep. 30, 2017
Jun. 30, 2012
shares
Dec. 31, 2017
USD ($)
plan
$ / shares
shares
Dec. 31, 2016
USD ($)
plan
$ / shares
shares
Dec. 31, 2015
USD ($)
plan
$ / shares
shares
Dec. 31, 2012
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Dec. 31, 2014
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Mar. 31, 2006
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Stock-Based Compensation                          
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense | $               $ 1,300,000          
Employee Stock [Member]                          
Stock-Based Compensation                          
Number of employee stock purchase plans | plan               1 2 1      
Minimum number of hours of weekly employment in order to qualify for eligibility in the plan               20 hours 20 hours 20 hours      
Number of shares reserved under the purchase plan                         1,600,000
Employee Stock Purchase Plan, Number Of Additional SharesToBe Authorized     1,500,000                    
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized 2,000,000 1,500,000   1,500,000                  
Minimum number of months of employment in a fiscal year in order to qualify for eligibility in the plan               5 months 5 months 5 months      
Offering period (in months)               6 months 6 months 6 months      
Percentage of the price at the beginning of the offering period or price at the end of each offering period to derive purchase price               85.00% 85.00% 85.00%      
Maximum share value per employee in any calendar year | $               $ 25,000 $ 25,000 $ 25,000      
Shares issued under employee stock purchase plans               615,370 548,357 544,391      
Weighted average price per share of shares issued (in dollars per share) | $ / shares               $ 10.47 $ 9.34 $ 9.36      
Shares available for issuance               836,273          
Stock-based compensation | $               $ 1,700,000 $ 1,600,000 $ 1,600,000      
Unrecognized compensation cost net of expected forfeitures | $               $ 700,000          
Expected weighted-average period for recognition of compensation cost (in years)               4 months          
Valuation assumptions                          
Expected stock price volatility rate minimum (as a percent)               25.00% 31.00% 34.00%      
Expected stock price volatility rate maximum (as a percent)               27.00% 33.00% 42.00%      
Risk free interest rate minimum (as a percent)               0.98% 0.41% 0.10%      
Risk free interest rate maximum (as a percent)               1.30% 0.50% 0.30%      
Expected term (in years)               6 months 6 months 6 months      
Weighted-average fair value of purchase rights granted under the purchase plan (in dollars per share) | $ / shares               $ 3.07 $ 2.88 $ 3.06      
Weighted-Average Grant-Date Fair Value                          
Granted (in dollars per share) | $ / shares               $ 3.07 $ 2.88 $ 3.06      
Stock Compensation Plan [Member]                          
Stock-Based Compensation                          
Number of shares reserved under the purchase plan 4,000,000             35,400,000         8,400,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized   10,000,000     6,500,000   6,500,000     4,000,000      
Shares available for issuance               5,051,147 7,305,368 11,173,545   10,724,228  
Options granted (in shares)               558,426 500,000 362,335      
Valuation assumptions                          
Dividend yield (as a percent)               0.00% 0.00% 0.00%      
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments, Other than Options Grants in Period Decrease in Available for Grant for Every Grant               1.5 1.5 1.5      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments, Other than Options, Forfeited in Period Increase in Available for Grant for Every Forfeiture               1.5 1.5 1.5      
Options                          
Stock-Based Compensation                          
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate                   41.00%      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate                   1.20%      
Options granted (in shares)               558,426 500,000 362,335      
Estimated total grant date fair value | $               $ 2,300,000 $ 2,300,000 $ 1,700,000      
Stock-based compensation | $               2,800,000 4,100,000 7,200,000      
Unrecognized compensation cost net of expected forfeitures | $               $ 3,400,000          
Expected weighted-average period for recognition of compensation cost (in years)               2 years 5 months 16 days          
Total fair value of options vested | $               $ 17,300,000 28,400,000 41,400,000      
Total intrinsic value of options exercised | $               7,500,000 8,000,000 6,800,000      
Proceeds from Stock Options Exercised | $               $ 9,400,000 $ 10,200,000 $ 8,800,000      
Valuation assumptions                          
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number               4,310,361 7,008,833 8,995,017   11,441,646  
Expected stock price volatility rate minimum (as a percent)               24.00% 34.00%        
Expected stock price volatility rate maximum (as a percent)               32.00% 36.00%        
Risk free interest rate minimum (as a percent)               1.80% 1.30%        
Risk free interest rate maximum (as a percent)               2.00% 1.70%        
Expected term (in years)                   5 years 11 months 19 days      
Weighted average grant date fair value (in dollars per share) | $ / shares               $ 4.09 $ 4.59 $ 4.59      
Restricted Stock and Stock Units [Member]                          
Stock-Based Compensation                          
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period           2 years 4 months 24 days   4 years          
Stock-based compensation | $               $ 22,900,000 $ 15,300,000 $ 6,300,000      
Unrecognized compensation cost net of expected forfeitures | $               $ 44,500,000          
Expected weighted-average period for recognition of compensation cost (in years)               2 years 4 months 2 days          
Total fair value of nonvested equity stock units at grant date | $               $ 40,000,000 $ 42,900,000 $ 33,300,000      
Valuation assumptions                          
Weighted-average fair value of purchase rights granted under the purchase plan (in dollars per share) | $ / shares               $ 13.02 $ 12.84 $ 11.62      
Nonvested equity stock and stock units                          
Nonvested at the beginning of the period (in shares)               4,863,056 3,008,118 673,864      
Granted (in shares)               3,075,396 3,344,448 2,865,878      
Vested (in shares)               (1,216,476) (789,864) (276,622)      
Forfeited (in shares)               (860,627) (699,646) (255,002)      
Nonvested at the end of the period (in shares)               5,861,349 4,863,056 3,008,118      
Weighted-Average Grant-Date Fair Value                          
Nonvested at the beginning of the period (in dollars per share) | $ / shares               $ 12.33 $ 11.32 $ 9.23      
Granted (in dollars per share) | $ / shares               13.02 12.84 11.62      
Vested (in dollars per share) | $ / shares               12.15 10.98 9.94      
Forfeited (in dollars per share) | $ / shares               12.61 11.94 10.64      
Nonvested at the end of the period (in dollars per share) | $ / shares               $ 12.68 $ 12.33 $ 11.32      
Performance Stock Units [Member]                          
Stock-Based Compensation                          
Stock-based compensation | $               $ 4,400,000 $ 2,800,000 $ 1,100,000      
Minimum                          
Stock-Based Compensation                          
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage               0.00%          
Minimum | Options                          
Valuation assumptions                          
Expected term (in years)               5 years 3 months 18 days 5 years 4 months 24 days        
Maximum                          
Stock-Based Compensation                          
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage               150.00%          
Maximum | Options                          
Valuation assumptions                          
Expected term (in years)               5 years 4 months 24 days 6 years 1 month 6 days        
Option One                          
Stock-Based Compensation                          
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period               60 months          
Option Two                          
Stock-Based Compensation                          
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period               48 months          
Stock Options with Market Condition [Member]                          
Stock-Based Compensation                          
Options granted (in shares)                     1,795,000    
Valuation assumptions                          
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number               0 1,135,000        
Chief Executive Officer [Member] | Performance Stock Units [Member]                          
Stock-Based Compensation                          
Stock-based compensation | $               $ 500,000