Note 13 - Selected Quarterly Financial Data (Unaudited) - Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 30, 2017	[1]	Sep. 30, 2017	[2]	Jul. 01, 2017	[3]	Apr. 01, 2017	[4]	Dec. 31, 2016	[5]	Oct. 01, 2016	[6]	Jul. 02, 2016	[7]	Apr. 02, 2016	[8]	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Net sales	$ 304,849		$ 317,889		$ 313,355		$ 285,441		$ 284,518		$ 280,331		$ 271,912		$ 219,398		$ 1,221,534	$ 1,056,159	$ 867,864
Gross profit	126,624		133,651		132,608		113,650		114,337		113,759		97,866		87,155		506,533	413,117	330,499
Operating income	50,780		58,609		60,270		48,852		40,988		27,526		29,702		32,428		218,511	130,644	104,157
Net income	$ (10,819)		$ 42,808		$ 48,638		$ 38,891		$ 27,245		$ 30,802		$ 27,152		$ 19,289		$ 119,519	$ 104,488	$ 80,866
Basic (in dollars per share)	$ (0.48)		$ 1.88		$ 2.13		$ 1.71		$ 1.20		$ 1.36		$ 1.21		$ 0.86
Diluted (in dollars per share)	$ (0.48)		$ 1.87		$ 2.11		$ 1.69		$ 1.19		$ 1.35		$ 1.20		$ 0.85

[1] In the fourth quarter of 2017, the Company recorded an estimated one-time tax charge of $49 million for the enactment of the Tax Cuts and Jobs Act for deemed repatriation of unremitted earnings of foreign subsidiaries, $1.4 million in acquisition and integration costs and $0.7 million in restructuring and production costs related to the transfer of Asian operations.

[2] In the third quarter of 2017, the Company recorded $4.8 million in acquisition and integration costs and $1.5 million in restructuring and production costs related to the transfer of Asian operations.

[3] In the second quarter of 2017, the Company recorded $0.3 million in acquisition and integration costs.

[4] In the first quarter of 2017, the Company $1.5 million in acquisition and integration costs

[5] In the fourth quarter of 2016, the Company recorded ($0.1) million gain related to the Company's transfer of its reed sensor manufacturing operations from the U.S. and China to the Philippines, $1.2 million of restructuring costs, $3.2 million in acquisition and integration costs and $0.3 million in non-cash inventory charges related to the 2016 acquisitions.

[6] In the third quarter of 2016, the Company recorded $0.9 million of restructuring costs, $5.9 million in acquisition and integration costs, $14.8 million of charges related to the impairment of the Custom Products reporting unit and $0.5 million in non-cash inventory charges as noted above.

[7] In the second quarter of 2016, the Company recorded $0.7 million related to the reed sensor manufacturing transfer as noted above, $0.1 million of restructuring costs, $6.1 million in acquisition and integration costs, $0.3 million in charges related to the closure of the manufacturing facility in Denmark and $6.9 million in non-cash inventory charges as noted above.

[8] In the first quarter of 2016, the Company recorded $1.0 million related to the reed sensor manufacturing transfer as noted above, $0.4 million of restructuring costs, $6.2 million in acquisition and integration costs, and $1.6 million in charges related to the closure of the manufacturing facility in Denmark.