Acquisitions and Dispositions - Acquisition (Details) - USD ($) $ in Thousands						12 Months Ended
	May 31, 2017	Apr. 26, 2016	Jul. 31, 2015	Jun. 18, 2015	Mar. 30, 2015	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015	Feb. 28, 2014
Business Acquisition [Line Items]
Cash paid for acquisition						$ 18,396	$ 20,533	$ 105,944
Allocated to:
Goodwill						130,293	123,993	$ 120,252
Noncontrolling interests						$ 13,917	$ 37,753
Customer Relationships [Member]
Intangible asset type:
Estimated Useful Life						20 years
Non-compete Agreements [Member] | Minimum [Member]
Intangible asset type:
Estimated Useful Life						3 years
Non-compete Agreements [Member] | Maximum [Member]
Intangible asset type:
Estimated Useful Life						5 years
Patents and Technology [Member] | Minimum [Member]
Intangible asset type:
Estimated Useful Life						10 years
Patents and Technology [Member] | Maximum [Member]
Intangible asset type:
Estimated Useful Life						15 years
Trade names and licenses [Member] | Minimum [Member]
Intangible asset type:
Estimated Useful Life						5 years
Trade names and licenses [Member] | Maximum [Member]
Intangible asset type:
Estimated Useful Life						10 years
Pexcor/Heatlink [Member]
Business Acquisition [Line Items]
Cash paid for acquisition	$ 16,300
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Total consideration	16,317
Allocated to:
Accounts receivable	2,809
Inventories	4,648
Other current assets	508
Property, plant, and equipment	2,024
Goodwill	4,071
Intangible assets	6,413	$ 6,413
Other assets	0
Total assets acquired	20,473
Accounts payable	3,633
Accrued wages & other employee costs	0
Other current liabilities	523
Long-term debt	0
Pension and other postretirement liabilities	0
Other noncurrent liabilities	0
Total liabilities assumed	4,156
Noncontrolling interests	0
Net assets acquired	$ 16,317
Pexcor/Heatlink [Member] | Customer Relationships [Member]
Allocated to:
Intangible assets		4,265
Pexcor/Heatlink [Member] | Non-compete Agreements [Member]
Allocated to:
Intangible assets		74
Pexcor/Heatlink [Member] | Patents and Technology [Member]
Allocated to:
Intangible assets		1,466
Pexcor/Heatlink [Member] | Trade names and licenses [Member]
Allocated to:
Intangible assets		608
Jungwoo-Mueller [Member]
Business Acquisition [Line Items]
Cash paid for acquisition		$ 20,500
Equity method investment, ownership percentage		60.00%
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Total consideration		$ 20,533
Allocated to:
Accounts receivable		5,551
Inventories		17,616
Other current assets		1,437
Property, plant, and equipment		24,191
Goodwill		223
Intangible assets		756	$ 756
Other assets		277
Total assets acquired		50,051
Accounts payable		7,252
Accrued wages & other employee costs		0
Other current liabilities		577
Long-term debt		8,659
Pension and other postretirement liabilities		799
Other noncurrent liabilities		582
Total liabilities assumed		17,869
Noncontrolling interests		11,649
Net assets acquired		$ 20,533
Jungwoo-Mueller [Member] | Customer Relationships [Member]
Allocated to:
Intangible assets			0
Jungwoo-Mueller [Member] | Non-compete Agreements [Member]
Allocated to:
Intangible assets			0
Jungwoo-Mueller [Member] | Patents and Technology [Member]
Allocated to:
Intangible assets			756
Jungwoo-Mueller [Member] | Trade names and licenses [Member]
Allocated to:
Intangible assets			0
Great Lakes Copper, Inc [Member]
Business Acquisition [Line Items]
Cash paid for acquisition			70,000
Cost of acquisition, post-closing working capital adjustment			1,500
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Total consideration			70,011
Allocated to:
Accounts receivable			26,079
Inventories			15,233
Other current assets			22
Property, plant, and equipment			22,771
Goodwill			23,208
Intangible assets			27,468		$ 27,468
Other assets			1,413
Total assets acquired			116,194
Accounts payable			36,026
Accrued wages & other employee costs			0
Other current liabilities			381
Long-term debt			0
Pension and other postretirement liabilities			5,655
Other noncurrent liabilities			4,121
Total liabilities assumed			46,183
Noncontrolling interests			0
Net assets acquired			$ 70,011
Great Lakes Copper, Inc [Member] | Customer Relationships [Member]
Allocated to:
Intangible assets					20,273
Great Lakes Copper, Inc [Member] | Non-compete Agreements [Member]
Allocated to:
Intangible assets					2,269
Great Lakes Copper, Inc [Member] | Patents and Technology [Member]
Allocated to:
Intangible assets					3,104
Great Lakes Copper, Inc [Member] | Trade names and licenses [Member]
Allocated to:
Intangible assets					1,822
Sherwood Valve Products, LLC [Member]
Business Acquisition [Line Items]
Cash paid for acquisition				$ 21,800
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Total consideration				21,795
Allocated to:
Accounts receivable				6,490
Inventories				11,892
Other current assets				260
Property, plant, and equipment				10,327
Goodwill				0
Intangible assets				(38)
Other assets				0
Total assets acquired				28,931
Accounts payable				6,022
Accrued wages & other employee costs				471
Other current liabilities				487
Long-term debt				0
Pension and other postretirement liabilities				0
Other noncurrent liabilities				156
Total liabilities assumed				7,136
Noncontrolling interests				0
Net assets acquired				$ 21,795
Turbotec Products, Inc. [Member]
Business Acquisition [Line Items]
Cash paid for acquisition					14,100
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Total consideration					14,138
Allocated to:
Accounts receivable					1,936
Inventories					3,247
Other current assets					72
Property, plant, and equipment					9,080
Goodwill					2,088
Intangible assets					880				$ 880
Other assets					59
Total assets acquired					17,362
Accounts payable					1,603
Accrued wages & other employee costs					356
Other current liabilities					51
Long-term debt					0
Pension and other postretirement liabilities					0
Other noncurrent liabilities					1,214
Total liabilities assumed					3,224
Noncontrolling interests					0
Net assets acquired					$ 14,138
Turbotec Products, Inc. [Member] | Customer Relationships [Member]
Allocated to:
Intangible assets									350
Turbotec Products, Inc. [Member] | Non-compete Agreements [Member]
Allocated to:
Intangible assets									90
Turbotec Products, Inc. [Member] | Patents and Technology [Member]
Allocated to:
Intangible assets									220
Turbotec Products, Inc. [Member] | Trade names and licenses [Member]
Allocated to:
Intangible assets									$ 220