Annual report pursuant to Section 13 and 15(d)

Dividends to Shareholders (Details Textual)

v3.10.0.1
Dividends to Shareholders (Details Textual) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Dec. 29, 2018
Sep. 29, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 30, 2017
Sep. 30, 2017
Jul. 01, 2017
Apr. 01, 2017
Dec. 31, 2016
Oct. 01, 2016
Jul. 02, 2016
Apr. 02, 2016
Dec. 29, 2018
Dec. 30, 2017
Dec. 31, 2016
Subsequent Event [Line Items]                              
Dividends declared                         $ 11,444 $ 10,273 $ 10,757
Common Stock, Dividends, Per Share, Declared $ 0.09 $ 0.09 $ 0.09 $ 0.09 $ 0.09 $ 0.09 $ 0.09 $ 0.09 $ 0.09 $ 0.09 $ 0.09 $ 0.09 $ 0.36 $ 0.38 $ 0.40
Dividend paid, date of payment                           Mar. 31, 2017 Mar. 31, 2016
Dividend paid, date of record                           Mar. 15, 2017 Mar. 15, 2016
Special Dividend [Member]                              
Subsequent Event [Line Items]                              
Common Stock, Dividends, Per Share, Declared                           $ 0.02 $ 0.04