Segment Information - Summary of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017		Jun. 30, 2018	Jul. 01, 2017
Summary of segment information [Abstract]
Net sales	$ 662,773	$ 614,266	[1]	$ 1,302,833	$ 1,192,186	[1]
Cost of goods sold	563,820	524,311	[1]	1,109,490	1,012,738	[1]
Depreciation and amortization	9,006	8,595	[1]	18,462	16,950	[1]
Selling, general, and administrative expense	38,428	36,299	[1]	72,485	71,873	[1]
(Gain) loss on sale of assets	(409)	(1,631)	[1]	3,060	(1,631)
Asset impairment				0	411	[2]
Operating income	51,928	46,692	[1]	99,336	92,256	[1]
Interest expense	(6,073)	(6,442)	[1]	(11,982)	(8,973)	[1]
Other income, net	586	342	[1]	1,146	936	[1]
Income before income taxes	46,441	40,592	[1]	88,500	84,219	[1]
Operating Segments [Member]
Summary of segment information [Abstract]
Net sales	668,246	613,984		1,312,605	1,196,875
Operating Segments [Member] | Piping Systems [Member]
Summary of segment information [Abstract]
Net sales	453,183	422,844		884,147	821,619
Cost of goods sold	384,821	364,261		757,716	708,907
Depreciation and amortization	5,744	5,591		11,622	10,933
Selling, general, and administrative expense	20,599	19,831		39,841	38,028
(Gain) loss on sale of assets	0	(1,631)		0	(1,631)
Operating income	42,019	34,792		74,968	65,382
Operating Segments [Member] | Industrial Metals [Member]
Summary of segment information [Abstract]
Net sales	175,891	154,504		353,223	304,341
Cost of goods sold	154,401	132,972		303,824	257,015
Depreciation and amortization	1,948	1,904		3,851	3,802
Selling, general, and administrative expense	3,449	3,239		6,822	6,788
(Gain) loss on sale of assets	0	0		0	0
Operating income	16,093	16,389		38,726	36,736
Operating Segments [Member] | Climate [Member]
Summary of segment information [Abstract]
Net sales	39,172	36,636		75,235	70,915
Cost of goods sold	30,688	27,449		57,974	53,013
Depreciation and amortization	627	615		1,248	1,244
Selling, general, and administrative expense	2,510	2,456		5,119	4,932
(Gain) loss on sale of assets	0	0		0	0
Operating income	5,347	6,116		10,894	11,726
Corporate and Eliminations [Member]
Summary of segment information [Abstract]
Net sales	(5,473)	282		(9,772)	(4,689)
Cost of goods sold	(6,090)	(371)		(10,024)	(6,197)
Depreciation and amortization	687	485		1,741	971
Selling, general, and administrative expense	11,870	10,773		20,703	22,125
(Gain) loss on sale of assets	(409)	0		3,060	0
Operating income	$ (11,531)	$ (10,605)		$ (25,252)	$ (21,588)

[1] The Condensed Consolidated Statements of Income for the quarter and six months ended July 1, 2017 have been adjusted to reflect the adoption of ASU 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. The components of net periodic benefit cost (income) other than the service cost component are included in other income, net in the Condensed Consolidated Statements of Income. Refer to Note 1 for further discussion.

[2] The Condensed Consolidated Statement of Cash Flows for the six months ended July 1, 2017 has been adjusted to reflect the adoption of ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash. The Condensed Consolidated Statements of Cash Flows reflects the changes during the periods in the total of cash, cash equivalents, and restricted cash. Therefore, restricted cash activity is included with cash when reconciling the beginning-of-period and end-of-period total amounts shown. Refer to Note 1 for further discussion.