Note 20 - Quarterly Data and Share Information (Unaudited) - Consolidated Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended													12 Months Ended
	Dec. 30, 2018	[1]	Sep. 30, 2018	[2]	Jul. 01, 2018	[3]	Apr. 01, 2018	Dec. 31, 2017	[4]	Oct. 01, 2017	Jul. 02, 2017	Apr. 02, 2017	[5]	Dec. 30, 2018		Dec. 31, 2017		Jan. 01, 2017
Net Sales	$ 337,059		$ 318,325		$ 283,626		$ 240,563	$ 266,210		$ 257,431	$ 251,700	$ 221,102		$ 1,179,573	[6]	$ 996,443	[6]	$ 958,617	[6]
Gross profit	121,682		99,945		109,148		93,582	101,778		98,544	97,897	87,802		424,357		386,021		368,644
Net income	$ 6,395		$ 8,172		$ 20,602		$ 15,084	$ 4,322		$ 19,439	$ 20,938	$ 8,547		$ 50,253		$ 53,246		$ 54,162
Basic income per share (in dollars per share)	$ 0.11		$ 0.14		$ 0.35		$ 0.25	$ 0.07		$ 0.32	$ 0.33	$ 0.13		$ 0.84		$ 0.86		$ 0.83
Diluted income per share (in dollars per share)	0.11		0.14		0.35		0.25	0.07		0.32	0.33	0.13		0.84		0.86		$ 0.83
Maximum [Member]
Share prices (in dollars per share)	23.50		24.50		26.10		26.25	25.70		22.60	21.05	19.93		23.50	[1]	25.70	[4]
Minimum [Member]
Share prices (in dollars per share)	$ 13.45		$ 21.70		$ 21.25		$ 22.10	$ 21.21		$ 18.30	$ 18.15	$ 17.18		$ 13.45	[1]	$ 21.21	[4]

[1] Results for the fourth quarter of 2018 include tax benefit of $6.7 million as a result of the finalization of the Company's analysis of the U.S. Tax Cuts and Jobs Act, as well as restructuring and asset impairment charges of $20.5 million. Results for the fourth quarter of 2018 include purchase price accounting amortization of $11.8 million and transaction related expense of $1.2 million.

[2] Results for the third quarter of 2018 include purchase price accounting amortization of $20.3 million and transaction related expenses of $2.4 million.

[3] Results for the second quarter of 2018 include transaction related expenses of $5.8 million.

[4] Results for the fourth quarter of 2017 include tax charges of $15.2 million as a result of the U.S. Tax Cuts and Jobs Act.

[5] Results for the first quarter of 2017 include restructuring and asset impairment charges of $7.3 million.

[6] Revenue attributed to geographic areas is based on the location of the customer.