Share-Based Payments - Share-based payments (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 28, 2020 USD ($) employee shares	Mar. 30, 2019 USD ($)	Dec. 28, 2019
Compensation expense
Total compensation expense for share-based payments	$ 423	$ 580
Number of employee | employee	2,706
Performance shares
Compensation expense
Unrecognized compensation expense	$ 2,100
Period over which unrecognized compensation expense is expected to be recognized	2 years 9 months 18 days
Restricted Stock
Compensation expense
Unrecognized compensation expense	$ 1,600
Period over which unrecognized compensation expense is expected to be recognized	2 years 8 months 12 days
Stock Option
Compensation expense
Unrecognized compensation expense	$ 400
Period over which unrecognized compensation expense is expected to be recognized	10 months 24 days
Additional pre-tax share based compensation expense	$ 100
Stock Option | Retired Executives [Member]
Compensation expense
Vested options, extended post-retirement exercise period	3 years		180 days
Vested Options With Extended Time Period | shares	83,759
Cost of Goods Sold
Compensation expense
Total compensation expense for share-based payments	$ 17	173
Selling, General and Administrative Expenses
Compensation expense
Total compensation expense for share-based payments	$ 406	$ 407