Note 6 - Restructuring (Details Textual) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019	Jun. 27, 2020
Q1 2020 Plan [Member]
Restructuring and Related Costs, Incurred Cost, Total	$ 0.6
Restructuring and Related Cost, Cost Incurred to Date	2.0		$ 2.0
Q2 2019 Sales Plan [Member]
Restructuring and Related Costs, Incurred Cost, Total	0.1	$ (0.1)	0.1	$ 2.3
Restructuring and Related Cost, Cost Incurred to Date					$ 2.0
June 2017 Plan [Member]
Restructuring and Related Costs, Incurred Cost, Total	2.0	$ 0.4	2.1	$ 2.4
Restructuring and Related Cost, Cost Incurred to Date	21.2		21.2
June 2017 Plan [Member] | Minimum [Member]
Restructuring and Related Cost, Expected Cost, Total	22.0		22.0
June 2017 Plan [Member] | Maximum [Member]
Restructuring and Related Cost, Expected Cost, Total	23.5		$ 23.5
June 2017 Plan [Member] | Vacated Facility [Member]
Restructuring and Related Costs, Incurred Cost, Total	$ 1.9