v3.8.0.1
Equity Award Plans - Employee Stock Purchase Plan (Details) - ESPP 2012 Plan [Member] - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
12 Months Ended
Mar. 30, 2012
Mar. 30, 2012
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Stock-based compensation:          
Shares authorized for issuance (in shares) 745 745      
Period for annual increase 8 years        
Percentage increase of outstanding shares   1.00%      
Maximum number of additional shares to be authorized (in shares) 1,490 1,490      
Shares available for future grant under the stock plans     1,608    
Fair value assumptions:          
Expected life (in years)     6 months 6 months 6 months
Dividend yield     0.00% 0.00% 0.00%
Shares issued (in shares)     183 200 161
Weighted average price per share (USD per share)     $ 73.02 $ 45.65 $ 41.84
Unamortized stock-based compensation expense     $ 1,864    
Average remaining vesting term     4 months 14 days    
Minimum [Member]          
Fair value assumptions:          
Volatility     29.00% 37.00% 42.00%
Risk-free interest rate     0.76% 0.38% 0.08%
Maximum [Member]          
Fair value assumptions:          
Volatility     37.00% 48.00% 47.00%
Risk-free interest rate     1.16% 0.45% 0.33%