Income Taxes (Details) $ in Thousands, kr in Millions	3 Months Ended		9 Months Ended
	Oct. 03, 2020 USD ($)	Sep. 28, 2019 USD ($)	Oct. 03, 2020 USD ($)	Oct. 03, 2020 NOK (kr)	Sep. 28, 2019 USD ($)
Income Taxes
Provision (benefit) for income taxes	$ (100)	$ 1,685	$ (306)		$ 28,481
Effective income tax rate (as a percent)	(3.30%)	7.70%	(9.30%)	(9.30%)	74.90%
Gross unrecognized tax benefits	$ 2,900		$ 2,900
Gross unrecognized tax benefits which would affect the effective tax rate if recognized	$ 2,000		2,000
Norwegian | 2013 | Under appeal
Income Taxes
Additional income tax expense			$ 15,200	kr 141.3