Segment Information - Summary of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016
Summary of segment information [Abstract]
Net sales	$ 614,266	$ 544,071	$ 1,192,186	$ 1,076,880
Cost of goods sold	524,311	456,060	1,012,738	902,702
Depreciation and amortization	8,595	9,061	16,950	17,981
Selling, general, and administrative expense	34,557	34,514	70,088	70,294
Operating income	46,803	44,436	92,410	85,903
Interest expense	(6,442)	(1,692)	(8,973)	(3,540)
Other income, net	231	515	782	760
Income before income taxes	40,592	43,259	84,219	83,123
Operating Segments [Member] | Piping Systems [Member]
Summary of segment information [Abstract]
Net sales	422,844	388,662	821,619	757,552
Cost of goods sold	364,261	333,356	708,907	647,148
Depreciation and amortization	5,591	5,787	10,933	11,436
Selling, general, and administrative expense	18,410	16,560	36,831	34,850
Operating income	34,582	32,959	64,948	64,118
Operating Segments [Member] | Industrial Metals [Member]
Summary of segment information [Abstract]
Net sales	154,504	127,737	304,341	262,258
Cost of goods sold	132,972	104,874	257,015	214,103
Depreciation and amortization	1,904	2,120	3,802	4,255
Selling, general, and administrative expense	2,864	3,619	6,094	6,864
Operating income	16,764	17,124	37,430	37,036
Operating Segments [Member] | Climate [Member]
Summary of segment information [Abstract]
Net sales	36,636	31,359	70,915	62,065
Cost of goods sold	27,449	22,448	53,013	46,153
Depreciation and amortization	615	618	1,244	1,217
Selling, general, and administrative expense	2,456	2,456	4,932	4,979
Operating income	6,116	5,837	11,726	9,716
Corporate and Eliminations [Member]
Summary of segment information [Abstract]
Net sales	282	(3,687)	(4,689)	(4,995)
Cost of goods sold	(371)	(4,618)	(6,197)	(4,702)
Depreciation and amortization	485	536	971	1,073
Selling, general, and administrative expense	10,827	11,879	22,231	23,601
Operating income	$ (10,659)	$ (11,484)	$ (21,694)	$ (24,967)