Segment Information - Summary of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Summary of segment information [Abstract]
Net sales	$ 550,363	$ 506,584	$ 1,742,549	$ 1,583,464
Cost of goods sold	471,262	424,668	1,484,000	1,327,370
Depreciation and amortization	8,266	9,016	25,216	26,997
Selling, general, and administrative expense	33,276	32,413	102,953	102,707
Asset impairments	0	3,000	411	3,000
Operating income	37,559	37,487	129,969	123,390
Interest expense	(5,237)	(1,830)	(14,210)	(5,370)
Other (expense) income, net	(458)	120	324	880
Income before income taxes	31,864	35,777	116,083	118,900
Piping Systems [Member]
Summary of segment information [Abstract]
Asset impairments		3,000		3,000
Operating Segments [Member] | Piping Systems [Member]
Summary of segment information [Abstract]
Net sales	384,078	351,557	1,205,697	1,109,109
Cost of goods sold	340,191	301,867	1,049,098	949,015
Depreciation and amortization	5,290	5,905	16,223	17,341
Selling, general, and administrative expense	17,873	16,647	54,293	51,497
Asset impairments			411
Operating income	20,724	24,138	85,672	88,256
Operating Segments [Member] | Industrial Metals [Member]
Summary of segment information [Abstract]
Net sales	147,578	131,350	451,919	393,608
Cost of goods sold	120,021	107,512	377,036	321,615
Depreciation and amortization	1,845	1,964	5,647	6,219
Selling, general, and administrative expense	2,667	3,125	8,761	9,989
Asset impairments		0	0	0
Operating income	23,045	18,749	60,475	55,785
Operating Segments [Member] | Climate [Member]
Summary of segment information [Abstract]
Net sales	32,488	30,003	103,403	92,068
Cost of goods sold	24,111	22,210	77,124	68,363
Depreciation and amortization	636	612	1,880	1,829
Selling, general, and administrative expense	2,312	2,357	7,244	7,336
Asset impairments		0	0	0
Operating income	5,429	4,824	17,155	14,540
Corporate and Eliminations [Member]
Summary of segment information [Abstract]
Net sales	(13,781)	(6,326)	(18,470)	(11,321)
Cost of goods sold	(13,061)	(6,921)	(19,258)	(11,623)
Depreciation and amortization	495	535	1,466	1,608
Selling, general, and administrative expense	10,424	10,284	32,655	33,885
Asset impairments		0	0	0
Operating income	$ (11,639)	$ (10,224)	$ (33,333)	$ (35,191)