Note 18 - Selected Quarterly Financial Data (Unaudited) (Details) - Quarterly Financial Information (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 28, 2013		Sep. 28, 2013		Jun. 29, 2013		Mar. 30, 2013		Dec. 29, 2012		Sep. 29, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 28, 2013	Dec. 29, 2012	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information [Abstract]
Net sales (in Dollars)	$ 198,129	[1]	$ 201,040	[2]	$ 187,766	[3]	$ 170,918	[3],[4]	$ 158,794	[4],[5]	$ 172,688	[5],[6]	$ 175,853		$ 160,578	[6],[7]	$ 757,853	$ 757,853	$ 667,913	$ 667,913	$ 664,955
Gross profit (in Dollars)	77,109	[1]	80,960	[2]	73,557	[3]	64,606	[3],[4]	59,407	[4],[5]	68,636	[5],[6]	69,562		60,862	[6],[7]		296,232	258,467		256,694
Operating income (in Dollars)	32,823	[1]	37,559	[2]	31,382	[3]	28,117	[3],[4]	18,019	[4],[5]	30,931	[5],[6]	32,096		25,824	[6],[7]	129,881	129,881	106,870	106,870	113,904
Net income (as previously reported) (in Dollars)	23,658	[1]	26,990	[2]	26,648	[3]	14,794	[3],[4]	9,841	[4],[5]	23,998	[5],[6]	23,604		17,889	[6],[7]		88,784	75,332		87,024
Equity method loss adjustments(g) (in Dollars)		[1],[7]		[2],[7]		[3],[7]		[3],[4],[7]	2,188	[4],[5],[7]	(1,220)	[5],[6],[7]	(641)	[7]	(326)	[6],[7]
Tax adjustment(d) (in Dollars)		[1],[4]		[2],[4]		[3],[4]	(3,306)	[4]		[4],[5]		[4],[6]		[4]		[4],[7]
Net income (Q1 2013 as restated) (in Dollars)	$ 23,658	[1]	$ 26,990	[2]	$ 26,648	[3]	$ 11,488	[3],[4]	$ 12,029	[4],[5]	$ 22,778	[5],[6]	$ 22,963		$ 17,563	[6],[7]		$ 88,784	$ 75,332		$ 87,024
Net income per share (as reported):
Basic	$ 1.05	[1]	$ 1.20	[2]	$ 1.19	[3]	$ 0.67	[3],[4]	$ 0.45	[4],[5]	$ 1.09	[5],[6]	$ 1.08		$ 0.83	[6],[7]
Diluted	$ 1.04	[1]	$ 1.19	[2]	$ 1.18	[3]	$ 0.66	[3],[4]	$ 0.44	[4],[5]	$ 1.08	[5],[6]	$ 1.07		$ 0.81	[6],[7]
Impact of equity method loss adjustments:
Basic		[1]		[2]		[3]		[3],[4]	$ 0.10	[4],[5]	$ (0.05)	[5],[6]	$ (0.03)		$ (0.02)	[6],[7]
Diluted		[1]		[2]		[3]		[3],[4]	$ 0.09	[4],[5]	$ (0.05)	[5],[6]	$ (0.03)		$ (0.01)	[6],[7]
Impact of tax adjustment:
Basic		[1]		[2]		[3]	$ (0.15)	[4]		[5]		[6]				[7]
Diluted		[1]		[2]		[3]	$ (0.15)	[4]		[5]		[6]				[7]
Net income per share (Q1 2013 as restated):
Basic	$ 1.05	[1]	$ 1.20	[2]	$ 1.19	[3]	$ 0.52	[3],[4]	$ 0.55	[4],[5]	$ 1.04	[5],[6]	$ 1.05		$ 0.81	[6],[7]		$ 3.98	$ 3.45		$ 3.96
Diluted	$ 1.04	[1]	$ 1.19	[2]	$ 1.18	[3]	$ 0.51	[3],[4]	$ 0.53	[4],[5]	$ 1.03	[5],[6]	$ 1.04		$ 0.80	[6],[7]		$ 3.94	$ 3.40		$ 3.90

[1] In the fourth quarter of 2013, the company recorded a $2.8 million charge to income tax expense related to the company's impairment of its investment in Shocking Technologies in the fourth quarter of 2012. (See Note 6). The company also recorded a $0.5 million non-cash credit related to the step-up of inventory from the Hamlin acquisition (See Note 2) and $0.2 million in acquisition expenses for the Hamlin acquisition.

[2] In the third quarter of 2013, the company recorded a $0.3 million non-cash charge related to the step-up of inventory from the Hamlin acquisition (See Note 2). The company also recorded $0.3 million in acquisition charges related to the Hamlin acquisition.

[3] In the second quarter of 2013, the company recorded a $1.7 million non-cash charge related to step-up of inventory from the Hamlin acquisition (See Note 2). The company also recorded $1.2 million in acquisition charges related to the Hamlin acquisition.

[4] In the first quarter of 2013, the company recorded a $10.7 million charge related to the impairment of Shocking Technologies. Additionally, the company restated net income for a $3.3 million charge to income tax expense related to the company's investment in Shocking Technologies (See Note 6).

[5] In the fourth quarter of 2012, the company recorded a $7.3 million charge related to the impairment and equity method losses of Shocking Technologies. (See Note 6). The company also recorded a $5.1 million charge related to a pension settlement (See Note 12).

[6] In the third quarter of 2012, the company recorded $0.5 million charge related to the impairment of the Dnsen, Germany property (See Note 11). The company also recorded $0.6 million in acquisition charges related to the Accel and Terra Power acquisitions and $0.4 million of non-cash charges related to the step-up of inventory from the Accel acquisition (See Note 2).

[7] In the first quarter of 2012, the company recorded a $0.2 million non-cash charge related to the step-up of inventory from the Selco acquisition (See Note 2).