Consolidated Statement of Shareholders' Equity (Parenthetical) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Apr. 01, 2018 |
Apr. 02, 2017 |
|
| Statement of Stockholders' Equity [Abstract] | ||
| Tax effect of unrealized gain (loss) on available-for-sale investments | $ (114) | $ 92 |