Goodwill and Intangible Assets (Details) - USD ($)	3 Months Ended	9 Months Ended
	Mar. 28, 2020	Sep. 26, 2020	Sep. 28, 2019	Dec. 28, 2019
Changes in the carrying amount of goodwill
Goodwill		$ 160,200,000		$ 164,921,000
Accumulated goodwill impairment		(71,900,000)		(76,417,000)
Balance at the beginning of the period, Goodwill, net	$ 88,504,000	88,504,000
Foreign currency translation adjustment and other		(214,000)
Balance at the end of the period, Goodwill, net		88,290,000
Decrease to goodwill from dissolution and final liquidation of GNU123 Liquidating Corporation	$ 4,500,000
Accumulated impairment		(71,900,000)		$ (76,417,000)
Intangible assets impairment losses		$ 0	$ 0