Inventories (Details 1) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 26, 2020	Jun. 28, 2019	Jun. 26, 2020	Jun. 28, 2019	Dec. 31, 2019
Inventory Disclosure [Abstract]
LIFO liquidation effect	$ 100	$ 100	$ 100	$ 100
Notional Amount of Nonderivative Instruments			$ 333,900		$ 309,300