Mueller Industries (MLI) 10-K 28 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 30, 2017	Feb. 23, 2018	Jul. 01, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	MUELLER INDUSTRIES INC
Entity Central Index Key	89,439
Current Fiscal Year End Date	--12-30
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 1,698,272,608
Entity Common Stock, Shares Outstanding		57,564,175
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 30, 2017

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Income Statement [Abstract]
Net sales	$ 2,266,073	$ 2,055,622	$ 2,100,002
Cost of goods sold	1,940,617	1,723,499	1,809,702
Depreciation and amortization	33,944	35,133	34,608
Selling, general, and administrative expense	139,580	137,499	130,358
Gain on sale of businesses	(1,491)	0	(15,376)
Impairment charges	1,466	6,778	0
Severance	0	0	3,442
Operating income	151,957	152,713	137,268
Interest expense	(19,502)	(7,387)	(7,667)
Environmental expense	(7,284)	(1,279)	(46)
Other income, net	1,801	1,983	2,234
Income before income taxes	126,972	146,030	131,789
Income tax expense	(37,884)	(48,137)	(43,382)
(Loss) income from unconsolidated affiliates, net of tax	(2,077)	1,861	0
Consolidated net income	87,011	99,754	88,407
Net income attributable to noncontrolling interests	(1,413)	(27)	(543)
Net income attributable to Mueller Industries, Inc.	$ 85,598	$ 99,727	$ 87,864
Weighted average shares for basic earnings per share (in shares)	56,925	56,572	56,316
Effect of dilutive stock-based awards (in shares)	559	597	652
Adjusted weighted average shares for diluted earnings per share (in shares)	57,484	57,169	56,968
Basic earnings per share (in dollars per share)	$ 1.50	$ 1.76	$ 1.56
Diluted earnings per share (in dollars per share)	1.49	1.74	1.54
Dividends per share (in dollars per share)	$ 8.4	$ 0.375	$ 0.300

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Statement of Comprehensive Income [Abstract]
Consolidated net income	$ 87,011	$ 99,754	$ 88,407
Other comprehensive income (loss), net of tax:
Foreign currency translation	13,174	(27,767)	(19,108)
Net change with respect to derivative instruments and hedging activities, net of tax of $(541), $(917), and $575	1,147	1,709	(1,056)
Net change in pension and postretirement obligation adjustments, net of tax of $(1,071), $(2,606), and $(3,221)	2,436	5,383	6,735
Attributable to unconsolidated affiliates, net of tax of $(505) and $(3,375)	895	5,975	0
Other, net	(380)	159	(49)
Total other comprehensive income (loss), net	17,272	(14,541)	(13,478)
Consolidated comprehensive income	104,283	85,213	74,929
Comprehensive (income) loss attributable to noncontrolling interests	(2,785)	2,548	867
Comprehensive income attributable to Mueller Industries, Inc.	$ 101,498	$ 87,761	$ 75,796

CONSOLIDATED STATEMENTS OF COM4

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Statement of Comprehensive Income [Abstract]
Derivative instruments, tax	$ (541)	$ (917)	$ 575
Pension & OPEB obligations, tax	(1,071)	(2,606)	$ (3,221)
Attributable to unconsolidated affiliates, tax	$ (505)	$ (3,375)

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 120,269	$ 351,317
Accounts receivable, less allowance for doubtful accounts of $980 in 2017 and $637 in 2016	244,795	256,291
Inventories	327,901	242,013
Other current assets	46,150	44,702
Total current assets	739,115	894,323
Property, plant, and equipment, net	304,321	295,231
Goodwill, net	130,293	123,993
Intangible assets, net	42,008	36,168
Investment in unconsolidated affiliates	76,434	77,110
Other noncurrent assets	28,002	20,651
Total Assets	1,320,173	1,447,476
Current liabilities:
Current portion of debt	16,480	13,655
Accounts payable	102,503	103,175
Accrued wages and other employee costs	33,546	35,121
Other current liabilities	89,723	67,041
Total current liabilities	242,252	218,992
Long-term debt, less current portion	448,592	213,709
Pension liabilities	11,606	14,890
Postretirement benefits other than pensions	17,107	16,383
Environmental reserves	23,699	21,208
Deferred income taxes	19,403	19,573
Other noncurrent liabilities	21,486	6,284
Total liabilities	784,145	511,039
Mueller Industries, Inc. stockholders' equity:
Preferred stock - $1.00 par value; shares authorized 5,000,000; none outstanding	0	0
Common stock - $.01 par value; shares authorized 100,000,000; issued 80,183,004; outstanding 57,809,509 in 2017 and 57,395,209 in 2016	802	802
Additional paid-in capital	274,585	273,345
Retained earnings	743,503	1,141,831
Accumulated other comprehensive loss	(51,056)	(66,956)
Treasury common stock, at cost	(445,723)	(450,338)
Total Mueller Industries, Inc. stockholders' equity	522,111	898,684
Noncontrolling interests	13,917	37,753
Total equity	536,028	936,437
Commitments and contingencies
Total Liabilities and Equity	$ 1,320,173	$ 1,447,476

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 980	$ 637
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	80,183,004	80,183,004
Common stock, shares outstanding (in shares)	57,809,509	57,395,209

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Operating activities:
Consolidated net income	$ 87,011	$ 99,754	$ 88,407
Reconciliation of net income to net cash provided by operating activities:
Depreciation	30,800	30,827	30,556
Amortization of intangibles	3,144	4,306	4,052
Amortization of debt issuance costs	303	569	432
Loss (income) from unconsolidated affiliates	2,077	(1,861)	0
Insurance proceeds - noncapital related	500	0	0
Stock-based compensation expense	7,450	6,387	6,244
Gain on sale of businesses	(1,491)	0	(15,376)
(Gain) loss on disposal of assets	(624)	(651)	561
Impairment charges	1,466	6,778	0
Income tax benefit from exercise of stock options	0	0	(972)
Deferred income tax (benefit) expense	(3,160)	6,998	(15,818)
Recovery of doubtful accounts receivable	0	(50)	(130)
Changes in assets and liabilities, net of businesses acquired and sold:
Receivables	(1,779)	(16,502)	51,660
Inventories	(86,286)	6,662	41,086
Other assets	(5,325)	5,808	12,449
Current liabilities	10,678	5,646	(45,585)
Other liabilities	64	1,518	436
Other, net	(833)	1,588	1,607
Net cash provided by operating activities	43,995	157,777	159,609
Investing activities:
Proceeds from sale of assets, net of cash transferred	31,564	10,304	5,538
Acquisition of businesses, net of cash acquired	(18,396)	(20,533)	(105,944)
Capital expenditures	(46,131)	(37,497)	(28,834)
Investment in unconsolidated affiliates	(3,317)	0	(65,900)
Net withdrawals from (deposits to) restricted cash balances	2,858	(5,331)	4,333
Net cash used in investing activities	(33,422)	(53,057)	(190,807)
Financing activities:
Dividends paid to stockholders of Mueller Industries, Inc.	(196,944)	(21,224)	(16,903)
Dividends paid to noncontrolling interests	(2,909)	(3,765)	0
Issuance of long-term debt	71,475	3,500	0
Repayments of long-term debt	(111,224)	(1,074)	(1,000)
(Repayment) issuance of debt by consolidated joint ventures, net	(3,369)	2,265	(23,567)
Net cash used to settle stock-based awards	(1,595)	(1,306)	(760)
Income tax benefit from exercise of stock options	0	0	972
Debt issuance costs	0	(957)	0
Net cash used in financing activities	(244,566)	(22,561)	(41,258)
Effect of exchange rate changes on cash	2,945	(5,686)	(4,834)
(Decrease) increase in cash and cash equivalents	(231,048)	76,473	(77,290)
Cash and cash equivalents at the beginning of the year	351,317	274,844	352,134
Cash and cash equivalents at the end of the year	$ 120,269	$ 351,317	$ 274,844

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]
Balance at beginning of year at Dec. 27, 2014		$ 802	$ 268,575	$ 992,798	$ (42,923)	$ (457,102)	$ 33,284
Balance at beginning of year (in shares) at Dec. 27, 2014		80,183				23,282
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under incentive stock option plans			(1,074)			$ 2,930
Stock-based compensation expense			6,244
Income tax benefit from exercise of stock options			972
Issuance of restricted stock			(3,559)			$ 3,784
Net income attributable to Mueller Industries, Inc.	$ 87,864			87,864
Dividends paid or payable to stockholders of Mueller Industries, Inc.				(17,119)
Total other comprehensive income (loss) attributable to Mueller Industries, Inc.	(13,478)				(12,067)
Issuance of shares under incentive stock option plans (in shares)						(149)
Repurchase of common stock						$ (2,840)
Repurchase of common stock (in shares)						84
Dividends paid to noncontrolling interests	0
Net income attributable to noncontrolling interests	(543)						543
Foreign currency translation	(19,108)						(1,410)
Issuance of restricted stock (in shares)						(193)
Balance at end of year at Dec. 26, 2015		$ 802	271,158	1,063,543	(54,990)	$ (453,228)	32,417
Balance at end of year (in shares) at Dec. 26, 2015		80,183				23,024
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under incentive stock option plans			(419)			$ 3,499
Stock-based compensation expense			6,387
Issuance of restricted stock			(3,781)			$ 3,780
Net income attributable to Mueller Industries, Inc.	99,727			99,727
Dividends paid or payable to stockholders of Mueller Industries, Inc.				(21,439)
Total other comprehensive income (loss) attributable to Mueller Industries, Inc.	(14,541)				(11,966)
Issuance of shares under incentive stock option plans (in shares)						(178)
Repurchase of common stock						$ (4,389)
Repurchase of common stock (in shares)						133
Purchase of Jungwoo-Mueller							11,649
Dividends paid to noncontrolling interests	3,765						(3,765)
Net income attributable to noncontrolling interests	(27)						27
Foreign currency translation	(27,767)						(2,575)
Issuance of restricted stock (in shares)						(191)
Balance at end of year at Dec. 31, 2016	936,437	$ 802	273,345	1,141,831	(66,956)	$ (450,338)	37,753
Balance at end of year (in shares) at Dec. 31, 2016		80,183				22,788
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under incentive stock option plans			(2,118)			$ 7,828
Stock-based compensation expense			7,450
Issuance of restricted stock			(4,092)			$ 4,092
Net income attributable to Mueller Industries, Inc.	85,598			85,598
Dividends paid or payable to stockholders of Mueller Industries, Inc.				(483,926)
Total other comprehensive income (loss) attributable to Mueller Industries, Inc.	17,272				15,900
Issuance of shares under incentive stock option plans (in shares)						(395)
Repurchase of common stock						$ (7,305)
Repurchase of common stock (in shares)						188
Sale of Mueller-Xingrong							(23,712)
Dividends paid to noncontrolling interests	2,909						(2,909)
Net income attributable to noncontrolling interests	(1,413)						1,413
Foreign currency translation	13,174						1,372
Issuance of restricted stock (in shares)						(208)
Balance at end of year at Dec. 30, 2017	$ 536,028	$ 802	$ 274,585	$ 743,503	$ (51,056)	$ (445,723)	$ 13,917
Balance at end of year (in shares) at Dec. 30, 2017		80,183				22,373

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Nature of Operations The principal business of Mueller Industries, Inc. is the manufacture and sale of copper tube and fittings; line sets; brass and copper alloy rod, bar, and shapes; aluminum and brass forgings; aluminum impact extrusions; plastic fittings and valves; refrigeration valves and fittings; fabricated tubular products; and steel nipples. The Company also resells imported brass and plastic plumbing valves, malleable iron fittings, faucets, and plumbing specialty products. The Company markets its products to the HVAC, plumbing, refrigeration, hardware, and other industries. Mueller’s operations are located throughout the United States and in Canada, Mexico, Great Britain, South Korea, and China. Fiscal Years The Company’s fiscal year ends on the last Saturday of December, and consisted of 52 weeks in 2017 , 53 weeks in 2016 , and 52 weeks in 2015 . These dates were December 30, 2017 , December 31, 2016 , and December 26, 2015 . Basis of Presentation The Consolidated Financial Statements include the accounts of Mueller Industries, Inc. and its majority-owned subsidiaries. The noncontrolling interests represent separate private ownership interests of 40 percent of Jungwoo Metal Ind. Co., LTD (Jungwoo-Mueller) and 49.5 percent of Jiangsu Mueller-Xingrong Copper Industries Limited (Mueller-Xingrong), which the Company sold during 2017 . See “ Note 2 – Acquisitions and Dispositions ” for additional information. Revenue Recognition Revenue is recognized when title and risk of loss pass to the customer, provided collection is determined to be probable and no significant obligations remain for the Company. Estimates for future rebates on certain product lines and product returns are recognized in the period in which the revenue is recorded. The cost of shipping product to customers is expensed as incurred as a component of cost of goods sold. Acquisitions Accounting for acquisitions requires the Company to recognize separately from goodwill the assets acquired and liabilities assumed at their acquisition date fair values. Goodwill is measured as the excess of the purchase price over the net amount allocated to the identifiable assets acquired and liabilities assumed. While management uses its best estimates and assumptions to accurately value assets acquired and liabilities assumed at the acquisition date, the estimates are inherently uncertain and subject to refinement. As a result, during the measurement period, which may be up to one year from the acquisition date, the Company may record adjustments to the assets acquired and liabilities assumed with the corresponding offset to goodwill. The operating results generated by the acquired businesses are included in the Consolidated Statements of Income from their respective dates of acquisition. Acquisition related costs are expensed as incurred. See “ Note 2 – Acquisitions and Dispositions ” for additional information. Cash Equivalents Temporary investments with original maturities of three months or less are considered to be cash equivalents. These investments are stated at cost. At December 30, 2017 and December 31, 2016 , temporary investments consisted of money market mutual funds, commercial paper, bank repurchase agreements, and U.S. and foreign government securities totaling $0.6 million and $40.9 million , respectively. Included in other current assets is restricted cash of $6.2 million and $9.0 million at December 30, 2017 and December 31, 2016 , respectively. These amounts represent required deposits into brokerage accounts that facilitate the Company’s hedging activities, and in 2016 included deposits that secured certain short-term notes issued under Mueller-Xingrong’s credit facility and funds received in conjunction with the New Markets Tax Credit transactions; see “ Note 10 – New Markets Tax Credit Transaction ” for additional information. Allowance for Doubtful Accounts The Company provides an allowance for receivables that may not be fully collected. In circumstances where the Company is aware of a customer’s inability to meet their financial obligations (e.g., bankruptcy filings or substantial credit rating downgrades), it records an allowance for doubtful accounts against amounts due to reduce the net recognized receivable to the amount it believes most likely will be collected. For all other customers, the Company recognizes an allowance for doubtful accounts based on its historical collection experience. If circumstances change (e.g., greater than expected defaults or an unexpected material change in a major customer’s ability to meet their financial obligations), the Company could change its estimate of the recoverability of amounts due by a material amount. Inventories The Company’s inventories are valued at the lower-of-cost-or-market. The material component of its U.S. copper tube and copper fittings inventories is valued on a LIFO basis and the non-material components of U.S. copper tube and copper fittings inventories are valued on a FIFO basis. The material component of its U.K. and Canadian copper tube inventories are valued on a FIFO basis. The material component of its brass rod and forgings inventories are valued on a FIFO basis. Certain inventories purchased for resale are valued on an average cost basis. Elements of cost in finished goods inventory in addition to the cost of material include depreciation, amortization, utilities, maintenance, production wages, and transportation costs. The market price of copper cathode and scrap is subject to volatility. During periods when open market prices decline below net book value, the Company may need to provide an allowance to reduce the carrying value of its inventory. In addition, certain items in inventory may be considered obsolete and, as such, the Company may establish an allowance to reduce the carrying value of those items to their net realizable value. Changes in these estimates related to the value of inventory, if any, may result in a materially adverse impact on the Company’s reported financial position or results of operations. The Company recognizes the impact of any changes in estimates, assumptions, and judgments in income in the period in which it is determined. See “ Note 4 – Inventories ” for additional information. Property, Plant, and Equipment Property, plant, and equipment is stated at cost less accumulated depreciation. Expenditures for major additions and improvements are capitalized, while minor replacements, maintenance, and repairs are charged to expense as incurred. Depreciation of buildings, machinery, and equipment is provided on the straight-line method over the estimated useful lives ranging from 20 to 40 years for buildings and five to 20 years for machinery and equipment. Leasehold improvements are amortized over the lesser of their useful life or the remaining lease term. The Company continually evaluates these assets to determine whether events or changes in circumstances have occurred that may warrant revision of the estimated useful life or whether the remaining balance should be evaluated for possible impairment. See “ Note 7 – Property, Plant, and Equipment, Net ” for additional information. Goodwill Goodwill is recognized for the excess of the purchase price over the fair value of tangible and identifiable intangible net assets of businesses acquired. Several factors give rise to goodwill in business acquisitions, such as the expected benefit from synergies of the combination and the existing workforce of the acquired business. Goodwill is evaluated annually for possible impairment as of the first day of the fourth quarter unless circumstances indicate the need to accelerate the timing of the evaluation. In the evaluation of goodwill impairment, management performs a qualitative assessment to determine if it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If the qualitative assessment is not conclusive, management compares the fair value of a reporting unit with its carrying amount and will recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value, not to exceed the total amount of goodwill allocated to the reporting unit. Fair value for the Company’s reporting units is determined using a combination of the income and market approaches (level 3 within the fair value hierarchy), incorporating market participant considerations and management’s assumptions on revenue growth rates, operating margins, discount rates and expected capital expenditures. The market approach measures the fair value of a business through the analysis of publicly traded companies or recent sales of similar businesses. The income approach uses a discounted cash flow model to estimate the fair value of reporting units based on expected cash flows (adjusted for capital investment required to support operations) and a terminal value. This cash flow stream is discounted to its present value to arrive at a fair value for each reporting unit. Future earnings are estimated using the Company’s most recent annual projections, applying a growth rate to future periods. Those projections are directly impacted by the condition of the markets in which the Company’s businesses participate. The discount rate selected for the reporting units is generally based on rates of return available for comparable companies at the date of valuation. Fair value determinations may include both internal and third-party valuations. See “ Note 8 – Goodwill and Other Intangible Assets ” for additional information. Investment in Unconsolidated Affiliates The Company owns a 50 percent interest in Tecumseh Products Holding LLC (Joint Venture), an unconsolidated affiliate that acquired Tecumseh Products Company (Tecumseh). The Company also owns a 50 percent interest in a second unconsolidated affiliate that provides financing to Tecumseh. These investments are recorded using the equity method of accounting, as the Company can exercise significant influence but does not own a majority equity interest or otherwise control the respective entities. Under the equity method of accounting, investments are stated at initial cost and are adjusted for subsequent additional investments and the Company’s proportionate share of earnings or losses and distributions. The Company records its proportionate share of the investee’s net income or loss one quarter in arrears as income (loss) from unconsolidated affiliates, net of tax, in the Consolidated Statements of Income. The Company’s proportionate share of the investees’ other comprehensive income (loss), net of income taxes, is recorded in the Consolidated Statements of Comprehensive Income and Consolidated Statements of Changes in Equity. In general, the equity investment in the unconsolidated affiliates is equal to the current equity investment plus the investees’ undistributed earnings. The investment in unconsolidated affiliates is assessed periodically for impairment and is written down when the carrying amount is not considered fully recoverable. See “ Note 9 – Investment in Unconsolidated Affiliates ” for additional information. Self-Insurance Accruals The Company is primarily self-insured for workers’ compensation claims and benefits paid under certain employee health care programs. Accruals are primarily based on estimated undiscounted cost of claims, which includes incurred but not reported claims, and are classified as accrued wages and other employee costs. Pension and Other Postretirement Benefit Plans The Company sponsors several qualified and nonqualified pension and other postretirement benefit plans in the U.S. and certain foreign locations. The Company recognizes the overfunded or underfunded status of the plans as an asset or liability in the Consolidated Balance Sheets with changes in the funded status recorded through comprehensive income in the year in which those changes occur. The obligations for these plans are actuarially determined and affected by assumptions, including discount rates, expected long-term return on plan assets for defined benefit pension plans, and certain employee-related factors, such as retirement age and mortality. The Company evaluates its assumptions periodically and makes adjustments as necessary. The expected return on plan assets is determined using the market value of plan assets. Differences between assumed and actual returns are amortized to the market value of assets on a straight-line basis over the average remaining service period of the plan participants using the corridor approach. The corridor approach defers all actuarial gains and losses resulting from variances between actual results and actuarial assumptions. These unrecognized gains and losses are amortized when the net gains and losses exceed 10 percent of the greater of the market value of the plan assets or the projected benefit obligation. The amount in excess of the corridor is amortized over the average remaining service period of the plan participants. For 2017 , the average remaining service period for the pension plans was nine years . See “ Note 12 –Benefit Plans ” for additional information. Environmental Reserves and Environmental Expenses The Company recognizes an environmental liability when it is probable the liability exists and the amount is reasonably estimable. The Company estimates the duration and extent of its remediation obligations based upon reports of outside consultants, internal and third party estimates and analyses of cleanup costs and ongoing monitoring costs, communications with regulatory agencies, and changes in environmental law. If the Company were to determine that its estimates of the duration or extent of its environmental obligations were no longer accurate, it would adjust environmental liabilities accordingly in the period that such determination is made. Estimated future expenditures for environmental remediation are not discounted to their present value. Environmental expenses that relate to ongoing operations are included as a component of cost of goods sold. Environmental expenses related to non-operating properties are presented below operating income in the Consolidated Statements of Income. See “ Note 13 – Commitments and Contingencies ” for additional information. Earnings Per Share Basic earnings per share is computed based on the weighted average number of common shares outstanding. Diluted earnings per share reflects the increase in weighted average common shares outstanding that would result from the assumed exercise of outstanding stock options and vesting of restricted stock awards calculated using the treasury stock method. Approximately 20 thousand and 190 thousand stock-based awards were excluded from the computation of diluted earnings per share for the years ended December 30, 2017 and December 31, 2016 , respectively, because they were antidilutive. Income Taxes Deferred income tax assets and liabilities are recognized when differences arise between the treatment of certain items for financial statement and tax purposes. Realization of certain components of deferred tax assets is dependent upon the occurrence of future events. The Company records valuation allowances to reduce its deferred tax assets to the amount it believes is more likely than not to be realized. These valuation allowances can be impacted by changes in tax laws, changes to statutory tax rates, and future taxable income levels and are based on the Company’s judgment, estimates, and assumptions regarding those future events. In the event the Company was to determine that it would not be able to realize all or a portion of the net deferred tax assets in the future, it would increase the valuation allowance through a charge to income tax expense in the period that such determination is made. Conversely, if it was to determine that it would be able to realize its deferred tax assets in the future, in excess of the net carrying amounts, the Company would decrease the recorded valuation allowance through a decrease to income tax expense in the period that such determination is made. The Company provides for uncertain tax positions and the related interest and penalties, if any, based upon management’s assessment of whether a tax benefit is more likely than not to be sustained upon examination by tax authorities. Tax benefits for uncertain tax positions that are recognized in the financial statements are measured as the largest amount of benefit, determined on a cumulative probability basis, that is more likely than not to be realized upon ultimate settlement. To the extent the Company prevails in matters for which a liability for an uncertain tax position is established or is required to pay amounts in excess of the liability, the Company’s effective tax rate in a given financial statement period may be affected. These estimates are highly subjective and could be affected by changes in business conditions and other factors. Changes in any of these factors could have a material impact on future income tax expense. See “ Note 14 – Income Taxes ” for additional information. Taxes Collected from Customers and Remitted to Governmental Authorities Taxes assessed by a governmental authority that are directly imposed on a revenue producing transaction between the Company and its customers, primarily value added taxes in foreign jurisdictions, are accounted for on a net (excluded from revenues and costs) basis. Stock-Based Compensation The Company has in effect stock incentive plans under which stock-based awards have been granted to certain employees and members of its Board of Directors. Stock-based compensation expense is recognized in the Consolidated Statements of Income as a component of selling, general, and administrative expense based on the grant date fair value of the awards. See “ Note 16 – Stock-Based Compensation ” for additional information. Concentrations of Credit and Market Risk Concentrations of credit risk with respect to accounts receivable are limited due to the large number of customers comprising the Company’s customer base, and their dispersion across different geographic areas and different industries, including HVAC, plumbing, refrigeration, hardware, automotive, OEMs, and others. The Company minimizes its exposure to base metal price fluctuations through various strategies. Generally, it prices an equivalent amount of copper raw material, under flexible pricing arrangements it maintains with its suppliers, at the time it determines the selling price of finished products to its customers. Derivative Instruments and Hedging Activities The Company’s earnings and cash flows are subject to fluctuations due to changes in commodity prices, foreign currency exchange rates, and interest rates. The Company uses derivative instruments such as commodity futures contracts, foreign currency forward contracts, and interest rate swaps to manage these exposures. All derivatives are recognized in the Consolidated Balance Sheets at their fair value. On the date the derivative contract is entered into, it is either a) designated as a hedge of (i) a forecasted transaction or the variability of cash flow to be paid (cash flow hedge) or (ii) the fair value of a recognized asset or liability (fair value hedge), or b) not designated in a hedge accounting relationship, even though the derivative contract was executed to mitigate an economic exposure (economic hedge), as the Company does not enter into derivative contracts for trading purposes. Changes in the fair value of a derivative that is qualified, designated, and highly effective as a cash flow hedge are recorded in stockholders’ equity within accumulated other comprehensive income (AOCI), to the extent effective, until they are reclassified to earnings in the same period or periods during which the hedged transaction affects earnings. Changes in the fair value of a derivative that is qualified, designated, and highly effective as a fair value hedge, along with the gain or loss on the hedged recognized asset or liability that is attributable to the hedged risk, are recorded in current earnings. Changes in the fair value of undesignated derivative instruments executed as economic hedges and the ineffective portion of designated derivatives are reported in current earnings. The Company documents all relationships between derivative instruments and hedged items, as well as the risk-management objective and strategy for undertaking various hedge transactions. This process includes linking all derivative instruments that are designated as fair value hedges to specific assets and liabilities in the Consolidated Balance Sheets and linking cash flow hedges to specific forecasted transactions or variability of cash flow. The Company also assesses, both at the hedge’s inception and on an ongoing basis, whether the designated derivative instruments that are used in hedging transactions are highly effective in offsetting changes in cash flow or fair values of hedged items. When a derivative instrument is determined not to be highly effective as a hedge or the underlying hedged transaction is no longer probable of occurring, hedge accounting is discontinued prospectively in accordance with the derecognition criteria for hedge accounting. The Company primarily executes derivative contracts with major financial institutions. These counterparties expose the Company to credit risk in the event of non-performance. The amount of such exposure is limited to the fair value of the contract plus the unpaid portion of amounts due to the Company pursuant to terms of the derivative instruments, if any. If a downgrade in the credit rating of these counterparties occurs, management believes that this exposure is mitigated by provisions in the derivative arrangements which allow for the legal right of offset of any amounts due to the Company from the counterparties with any amounts payable to the counterparties by the Company. As a result, management considers the risk of loss from counterparty default to be minimal. See “ Note 6 – Derivative Instruments and Hedging Activities ” for additional information. Fair Value of Financial Instruments The carrying amounts for cash and cash equivalents, accounts receivable, and accounts payable approximate fair value due to the short-term maturity of these instruments. The fair value of long-term debt at December 30, 2017 approximates the carrying value on that date. The estimated fair values were determined based on quoted market prices and the current rates offered for debt with similar terms and maturities. The fair value of long-term debt is classified as level 2 within the fair value hierarchy. This classification is defined as a fair value determined using market-based inputs other than quoted prices that are observable for the liability, either directly or indirectly. Foreign Currency Translation For foreign subsidiaries in which the functional currency is not the U.S. dollar, balance sheet accounts are translated at exchange rates in effect at the end of the year and income statement accounts are translated at average exchange rates for the year. Translation gains and losses are included in equity as a component of AOCI. Transaction gains and losses that arise from exchange rate fluctuations on transactions denominated in a currency other than the functional currency are recognized in selling, general, and administrative expense in the Consolidated Statements of Income. Included in the Consolidated Statements of Income were net transaction losses of $0.4 million in 2017 , gains of $0.4 million in 2016 , and losses of $1.7 million in 2015 . Use of and Changes in Estimates The preparation of financial statements in conformity with generally accepted accounting principles in the United States (U.S. GAAP) requires management to make estimates, assumptions, and judgments that affect the amounts reported in the financial statements and accompanying notes. Management makes its best estimate of the ultimate outcome for these items based on historical trends and other information available when the financial statements are prepared. Changes in estimates are recognized in accordance with the accounting rules for the estimate, which is typically in the period when new information becomes available to management. Areas where the nature of the estimate makes it reasonably possible that actual results could materially differ from amounts estimated include but are not limited to: pension and other postretirement benefit plan obligations, tax liabilities, loss contingencies, litigation claims, environmental reserves, and impairment assessments on long-lived assets (including goodwill). Change in Segment Reporting At the beginning of fiscal year 2016 , the Company made changes to its management reporting structure as a result of a change in the way the Chief Executive Officer, who serves as the Chief Operating Decision Maker, manages and evaluates the business, makes key operating decisions, and allocates resources. Previously, the Company had two reportable segments: Plumbing & Refrigeration and OEM. During 2016 , the Company realigned its operating segments into three reportable segments: Piping Systems, Industrial Metals, and Climate. Management has recast certain prior year amounts to conform to the current year presentation. See “ Note 3 - Segment Information ” for additional information. Recently Adopted Accounting Standard In January 2017, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment . The ASU eliminates step two from the goodwill impairment test and instead requires an entity to perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity is required to recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The updated guidance requires a prospective adoption. The guidance is effective for the Company beginning in 2020 and early adoption is permitted. The Company adopted the ASU during the fourth quarter of 2017 and the adoption had no impact on its Consolidated Financial Statements. Recently Issued Accounting Standards In February 2018, the FASB issued ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . The ASU permits entities to reclassify tax effects stranded in AOCI as a result of tax reform to retained earnings. The guidance is effective for the Company in interim and annual periods beginning in 2019. Early adoption is permitted and can be applied retrospectively or in the period of adoption. The Company does not expect the adoption of the standard to have a material impact on its Consolidated Financial Statements. In March 2017, the FASB issued ASU No. 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . The ASU requires employers that sponsor defined benefit pension and/or other postretirement benefit plans to present the service cost component of net periodic benefit cost in the same income statement line item(s) as other employee compensation costs arising from services rendered during the period and other components of net periodic benefits cost separately from the line item(s) that includes the service cost and outside of any subtotal of operating income. The guidance is effective for the Company in interim and annual periods beginning in 2018. Early adoption is permitted as of the beginning of an annual period for which financial statements have not been issued or made available for issuance. The Company does not expect the adoption of the standard to have a material impact on its Consolidated Financial Statements. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business . The ASU provides guidance to assist entities in evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The updated guidance requires a prospective adoption. Early adoption is permitted. This update will be effective for the Company beginning in 2018. The Company does not expect the provisions of the ASU to have a material impact on its Consolidated Financial Statements. In December 2016, the FASB issued ASU No. 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers . The ASU provides correction or improvement to the guidance previously issued in ASU 2014-09, Revenue from Contracts with Customers (Topic 606) . Under the ASU, an entity will recognize revenue to depict the transfer of promised goods or services to customers at an amount that reflects the consideration that it expects to receive in exchange for the goods or services. It also requires more detailed disclosures to enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. This guidance is effective for the Company at the beginning of 2018. The standard permits the use of either the full retrospective or cumulative transition effect (modified retrospective) method. The ASU requires revenue to be recognized over time (i.e., throughout the production process) rather than at a point in time (generally upon shipment to the customer) if performance does not create an asset with an alternative use to the entity and the entity has an enforceable right to payment for performance completed to date. The Company has evaluated specific contract terms, primarily within the Industrial Metals and Climate segments, related to the production of customized products and payment rights and determined that there will be no significant changes to the timing of revenue recognition under the ASU. As part of the overall evaluation of the standard, the Company has assessed changes to its accounting policies, practices, and internal controls over financial reporting to support the standard. The Company does not expect the adoption of the standard to have a material impact on its Consolidated Financial Statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash . The ASU requires entities to show the changes in the total of cash, cash equivalents, restricted cash, and restricted cash equivalents in the statement of cash flows. As a result, entities will no longer present transfers between cash and cash equivalents and restricted cash and restricted cash equivalents in the statement of cash flows. The guidance will be applied retrospectively and is effective for the Company beginning in 2018. Early adoption is permitted. The Company does not expect the adoption of the standard to have a material impact on its Consolidated Financial Statements. In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory . The ASU requires companies to account for the income tax effects of intercompany transfers of assets other than inventory when the transfer occurs. Companies will still be required to defer the income tax effects of intercompany inventory transactions in an exception to the income tax accounting guidance. The guidance is effective for the Company beginning in 2018. Early adoption is permitted as of the beginning of an annual period. The Company is still evaluating the effects that the provisions of the ASU will have on its Consolidated Financial Statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . The ASU requires an entity to recognize a right-of-use asset and lease liability for all leases with terms of more than 12 months. Recognition, measurement and presentation of expenses will depend on classification as a financing or operating lease. The amendments also require certain quantitative and qualitative disclosures about leasing arrangements. The ASU will be effective for interim and fiscal periods beginning in 2018. Early adoption is permitted. Currently the guidance requires a modified retrospective adoption, but in January 2018 the FASB proposed ASU No. 2018-01, Leases (Topic 842) , which if approved will allow entities to elect a si

Acquisitions and Dispositions

Acquisitions and Dispositions	12 Months Ended
	Dec. 30, 2017
Acquisitions and Dispositions [Abstract]
Acquisitions and Dispositions	Acquisitions and Dispositions 2017 Acquisition On May 31, 2017, the Company entered into a share purchase agreement pursuant to which the Company acquired all of the outstanding shares of Pexcor Manufacturing Company Inc. and Heatlink Group Inc. (collectively, Heatlink Group) for approximately $16.3 million in cash, net of working capital adjustments. Heatlink Group, based out of Calgary, Alberta, Canada, produces and sells a complete line of products for PEX plumbing and radiant systems. The business complements the Company’s existing businesses within the Piping Systems segment. 2016 Acquisition On April 26, 2016, the Company entered into an agreement providing for the purchase of a 60 percent equity interest in Jungwoo-Mueller for approximately $20.5 million in cash. Jungwoo-Mueller, which manufactures copper-based pipe joining products, is headquartered in Seoul, South Korea and serves markets worldwide. This business complements the Company’s existing copper fittings businesses in the Piping Systems segment and is reported in the Company’s Consolidated Financial Statements one month in arrears. 2015 Acquisitions Great Lakes Copper On July 31, 2015, the Company entered into a Share Purchase Agreement with Great Lakes Copper, Inc. providing for the purchase of all of the outstanding shares of Great Lakes Copper Ltd. (Great Lakes) for $70.0 million in cash, including a $1.5 million post-closing working capital adjustment. Great Lakes manufactures copper tube products in Canada. This acquisition complements the Company’s existing copper tube businesses in the Piping Systems segment. Sherwood Valve Products On June 18, 2015, the Company entered into a Membership Interest Purchase Agreement with Sherwood Valve Products Inc. providing for the purchase of all of the outstanding equity interests of Sherwood Valve LLC (Sherwood) for $21.8 million in cash, net of a post-closing working capital adjustment. Sherwood manufactures valves and fluid control solutions for the HVAC, refrigeration, and compressed gas markets. The acquisition of Sherwood complements our existing compressed gas business in the Industrial Metals segment. Turbotec Products, Inc. On March 30, 2015, the Company entered into a Stock Purchase Agreement with Turbotec Products PLC providing for the purchase of all of the outstanding capital stock of Turbotec Products, Inc. (Turbotec) for approximately $14.1 million in cash, net of a post-closing working capital adjustment. Turbotec manufactures coaxial heat exchangers and twisted tubes for the heating, ventilation, and air-conditioning (HVAC), geothermal, refrigeration, swimming pool heat pump, marine, ice machine, commercial boiler, and heat reclamation markets. The acquisition of Turbotec complements the Company’s existing refrigeration business, a component of the Climate segment. These acquisitions were accounted for using the acquisition method of accounting whereby the total purchase price was allocated to tangible and intangible assets acquired and liabilities assumed based on respective fair values. The following table summarizes the allocation of the purchase price to acquire these businesses, which was financed by available cash balances, as well as the assets acquired and liabilities assumed at the respective acquisition dates. The purchase price allocation for Heatlink Group is provisional as of December 30, 2017 and subject to change upon completion of the final valuation of the long-lived assets during the measurement period. During 2017 , the valuation of the Jungwoo-Mueller acquisition was finalized and changes to the purchase price allocation from the amounts presented in the Company’s 2016 Consolidated Financial Statements were immaterial. (in thousands) Heatlink Group Jungwoo-Mueller Great Lakes Sherwood Turbotec Total consideration $ 16,317 $ 20,533 $ 70,011 $ 21,795 $ 14,138 Allocated to: Accounts receivable 2,809 5,551 26,079 6,490 1,936 Inventories 4,648 17,616 15,233 11,892 3,247 Other current assets 508 1,437 22 260 72 Property, plant, and equipment 2,024 24,191 22,771 10,327 9,080 Goodwill 4,071 223 23,208 (1) — 2,088 Intangible assets 6,413 756 27,468 (38 ) 880 Other assets — 277 1,413 — 59 Total assets acquired 20,473 50,051 116,194 28,931 17,362 Accounts payable 3,633 7,252 36,026 6,022 1,603 Accrued wages & other employee costs — — — 471 356 Other current liabilities 523 577 381 487 51 Long-term debt — 8,659 — — — Pension and other postretirement liabilities — 799 5,655 — — Other noncurrent liabilities — 582 4,121 156 1,214 Total liabilities assumed 4,156 17,869 46,183 7,136 3,224 Noncontrolling interest — 11,649 — — — Net assets acquired $ 16,317 $ 20,533 $ 70,011 $ 21,795 $ 14,138 (1) Tax-deductible goodwill The fair value of the noncontrolling interest at Jungwoo-Mueller was determined based on the proportionate share of consideration transferred and adjusted for lack of control and marketability based on the average of the classic put option model and the Finnerty Formula. The following details the total intangible assets identified in the allocation of the purchase price at the respective acquisition dates: (in thousands) Estimated Useful Life Heatlink Group Jungwoo-Mueller Great Lakes Turbotec Intangible asset type: Customer relationships 20 years $ 4,265 $ — $ 20,273 $ 350 Non-compete agreements 3-5 years 74 — 2,269 90 Patents and technology 10-15 years 1,466 756 3,104 220 Trade names, licenses, and other 5-10 years 608 — 1,822 220 Total intangible assets $ 6,413 $ 756 $ 27,468 $ 880 2017 Disposition On June 21, 2017, the Company entered into a definitive equity transfer agreement with Jiangsu Xingrong Hi-Tech Co. Ltd. and Jiangsu Baiyang Industries Co. Ltd. (Baiyang), together, the minority partners in Mueller-Xingrong (the Company’s Chinese joint venture), pursuant to which the Company sold its 50.5 percent equity interest in Mueller-Xingrong to Baiyang for approximately $18.3 million . Mueller-Xingrong manufactured engineered copper tube primarily for air-conditioning applications in China and was included in the Piping Systems segment. Mueller-Xingrong reported net sales of $67.3 million and net losses of $9 thousand in 2017 , compared to net sales of $121.5 million and net income of $62 thousand in 2016 , and net sales of $155.9 million and net income of $555 thousand in 2015 . The carrying value of the assets disposed totaled $56.8 million , consisting primarily of accounts receivable, inventories, and long-lived assets. The carrying value of the liabilities disposed (consisting primarily of current debt and accounts payable), noncontrolling interest, and amounts recognized in accumulated other comprehensive income (AOCI) totaled $36.2 million . Since the disposal constituted a complete liquidation of the Company’s investment in a foreign entity, the Company removed from AOCI and recognized a cumulative translation gain of $3.8 million . As a result of the disposal, the Company recognized a net gain on the sale of this business of $1.5 million in the Consolidated Financial Statements. 2015 Disposition On June 1, 2015, the Company sold certain assets. Simultaneously, the Company entered into a lease agreement with the purchaser of the assets for their continued use for a period of approximately 22 months (Lease Period). The total sales price was $20.2 million , of which $5.0 million was received on June 1, 2015, $5.0 million was received on December 30, 2016, and $10.2 million was received on August 28, 2017. This transaction resulted in a pre-tax gain of $15.4 million in the second quarter of 2015, or 17 cents per diluted share after tax. This gain was recognized in the Piping Systems segment. The net book value of the assets disposed was $2.3 million . For goodwill testing purposes, these assets were part of the Domestic Piping Systems (DPS) reporting unit, which is a component of the Company’s Piping Systems segment. Because these assets met the definition of a business, $2.4 million of the DPS reporting unit’s goodwill balance was allocated to the disposal group based on the relative fair values of the asset group that was disposed and the portion of the DPS reporting unit that was retained.

Segment Information

Segment Information	12 Months Ended
	Dec. 30, 2017
Segment Reporting [Abstract]
Segment Information	Segment Information The Company’s reportable segments are Piping Systems, Industrial Metals, and Climate. Each of the reportable segments is composed of certain operating segments that are aggregated primarily by the nature of products offered as follows: Piping Systems Piping Systems is composed of the following operating segments: DPS, Great Lakes Copper, Heatlink Group, European Operations, Trading Group, and Jungwoo-Mueller (the Company’s South Korean joint venture). DPS manufactures copper tube and fittings, plastic fittings, and line sets. These products are manufactured in the U.S., sold in the U.S., and exported to markets worldwide. Outside the U.S., Great Lakes Copper manufactures copper tube and line sets in Canada and sells the products primarily in the U.S. and Canada, Heatlink Group produces a complete line of products for PEX plumbing and radiant systems in Canada and sells these products in Canada and the U.S., and the European Operations manufacture copper tube in the U.K. which is sold primarily in Europe. The Trading Group manufactures pipe nipples and imports and resells brass and plastic plumbing valves, malleable iron fittings, faucets, and plumbing specialty products in the U.S. and Mexico. Jungwoo-Mueller manufactures copper-based joining products that are sold worldwide. The Piping Systems segment’s products are sold primarily to plumbing, refrigeration, and air-conditioning wholesalers, hardware wholesalers and co-ops, building product retailers, and air-conditioning OEMs. During 2017 , the segment recognized a gain of $1.5 million on the sale of the Company’s interest in Mueller-Xingrong and impairment charges of $1.5 million on certain copper fittings manufacturing equipment. During 2016 , the segment recognized impairment charges of $6.1 million on fixed assets used for product development. During 2015 , the segment recognized approximately $3.4 million of severance costs related to the reorganization of the European Operations as a result of the acquisition of Yorkshire Copper Tube in 2014. Industrial Metals Industrial Metals is composed of the following operating segments: Brass Rod & Copper Bar Products, Impacts & Micro Gauge, and Brass Value-Added Products. These businesses manufacture brass rod, impact extrusions, and forgings, as well as a wide variety of end products including plumbing brass, automotive components, valves, fittings, and gas assemblies. These products are manufactured in the U.S. and sold primarily to OEMs in the U.S., many of which are in the industrial, transportation, construction, heating, ventilation, and air-conditioning, plumbing, refrigeration, and energy markets. During 2016 , the segment recognized impairment charges of $0.7 million on fixed assets related to the rationalization of Sherwood. Climate Climate is composed of the following operating segments: Refrigeration Products, Fabricated Tube Products, Westermeyer, and Turbotec. These domestic businesses manufacture and fabricate valves, assemblies, high pressure components, and coaxial heat exchangers primarily for the heating, ventilation, air-conditioning, and refrigeration markets in the U.S. Performance of segments is generally evaluated by their operating income. Summarized product line, geographic, and segment information is shown in the following tables. Geographic sales data indicates the location from which products are shipped. Unallocated expenses include general corporate expenses, plus certain charges or credits not included in segment activity. During 2017 , 2016 , and 2015 , no single customer exceeded 10 percent of worldwide sales. Net Sales by Major Product Line: (In thousands) 2017 2016 2015 Tube and fittings $ 1,260,105 $ 1,072,242 $ 1,053,761 Brass rod and forgings 450,063 371,237 436,456 OEM components, tube & assemblies 272,567 327,327 342,651 Valves and plumbing specialties 200,409 209,217 198,012 Other 82,929 75,599 69,122 $ 2,266,073 $ 2,055,622 $ 2,100,002 Geographic Information: (In thousands) 2017 2016 2015 Net sales: United States $ 1,556,825 $ 1,400,893 $ 1,519,456 United Kingdom 231,039 197,039 240,823 Canada 280,140 237,162 97,967 Asia 121,295 149,875 162,664 Mexico 76,774 70,653 79,092 $ 2,266,073 $ 2,055,622 $ 2,100,002 (In thousands) 2017 2016 2015 Long-lived assets: United States $ 238,752 $ 223,099 $ 223,398 United Kingdom 17,661 15,978 19,982 Canada 21,327 18,928 20,460 Asia 25,973 36,722 15,863 Mexico 608 504 521 $ 304,321 $ 295,231 $ 280,224 Summarized segment information is as follows: For the Year Ended December 30, 2017 (In thousands) Piping Systems Industrial Metals Climate Corporate and Eliminations Total Net sales $ 1,564,950 $ 602,131 $ 131,448 $ (32,456 ) $ 2,266,073 Cost of goods sold 1,369,161 506,973 98,851 (34,368 ) 1,940,617 Depreciation and amortization 21,777 7,516 2,513 2,138 33,944 Selling, general, and administrative expense 74,479 11,890 9,759 43,452 139,580 Gain on sale of businesses (1,491 ) — — — (1,491 ) Impairment charges 1,466 — — — 1,466 Operating income 99,558 75,752 20,325 (43,678 ) 151,957 Interest expense (19,502 ) Environmental expense (7,284 ) Other income, net 1,801 Income before income taxes $ 126,972 Segment information (continued): For the Year Ended December 31, 2016 (In thousands) Piping Systems Industrial Metals Climate Corporate and Eliminations Total Net sales $ 1,429,589 $ 521,060 $ 119,758 $ (14,785 ) $ 2,055,622 Cost of goods sold 1,228,949 420,905 89,927 (16,282 ) 1,723,499 Depreciation and amortization 22,421 8,162 2,437 2,113 35,133 Selling, general, and administrative expense 68,218 13,162 9,661 46,458 137,499 Impairment charges 6,115 663 — — 6,778 Operating income 103,886 78,168 17,733 (47,074 ) 152,713 Interest expense (7,387 ) Environmental expense (1,279 ) Other income, net 1,983 Income before income taxes $ 146,030 For the Year Ended December 26, 2015 (In thousands) Piping Systems Industrial Metals Climate Corporate and Eliminations Total Net sales $ 1,436,689 $ 567,467 $ 110,727 $ (14,881 ) $ 2,100,002 Cost of goods sold 1,245,929 491,567 86,894 (14,688 ) 1,809,702 Depreciation and amortization 22,559 7,503 2,257 2,289 34,608 Selling, general, and administrative expense 66,903 10,955 9,117 43,383 130,358 Gain on sale of businesses (15,376 ) — — — (15,376 ) Severance 3,442 — — — 3,442 Operating income 113,232 57,442 12,459 (45,865 ) 137,268 Interest expense (7,667 ) Environmental expense (46 ) Other income, net 2,234 Income before income taxes $ 131,789 Segment information (continued): (In thousands) 2017 2016 2015 Expenditures for long-lived assets (including those resulting from business acquisitions): Piping Systems $ 18,124 $ 56,286 $ 41,900 Industrial Metals 5,322 3,302 16,603 Climate 2,191 2,045 12,373 General Corporate 22,518 55 136 $ 48,155 $ 61,688 $ 71,012 During the fourth quarter of 2017 , the Company took early delivery of a Corporate aircraft to replace its existing aircraft. Subsequent to year-end, the existing aircraft was taken out of service and classified as held-for-sale, and the Company expects to recognize an impairment charge of approximately $3.3 million in the first quarter of 2018. The Company expects to sell the aircraft in 2018. Segment assets: Piping Systems $ 801,468 $ 826,663 $ 811,343 Industrial Metals 212,638 160,478 153,102 Climate 73,458 66,968 61,672 General Corporate 232,609 393,367 312,684 $ 1,320,173 $ 1,447,476 $ 1,338,801

Inventories

Inventories	12 Months Ended
	Dec. 30, 2017
Inventory Disclosure [Abstract]
Inventories	Inventories (In thousands) 2017 2016 Raw materials and supplies $ 108,397 $ 57,387 Work-in-process 46,158 42,227 Finished goods 180,143 149,288 Valuation reserves (6,797 ) (6,889 ) Inventories $ 327,901 $ 242,013 Inventories valued using the LIFO method totaled $26.5 million at December 30, 2017 and $14.4 million at December 31, 2016 . At December 30, 2017 and December 31, 2016 , the approximate FIFO cost of such inventories was $ 111.0 million and $ 76.6 million , respectively. Additionally, the Company values certain inventories purchased for resale on an average cost basis. The value of those inventories was $ 43.9 million at December 30, 2017 and $ 43.8 million at December 31, 2016 . During 2016 , inventory quantities valued using the LIFO method declined, which resulted in liquidation of LIFO inventory layers. This liquidation resulted primarily from intercompany sales; therefore $ 2.5 million of the $ 3.3 million loss related to the LIFO liquidation was deferred at the end of 2016 . The deferred loss increased cost of goods sold in the first quarter of 2017 when the inventory was sold to third parties. During September 2017, the Company experienced a casting outage at its brass rod mill which impaired its ability to melt scrap returns, causing an excess build of $38.9 million in inventory. At the end of 2017 and 2016 , the FIFO value of inventory consigned to others was $ 4.4 million and $ 2.5 million , respectively.

Consolidated Financial Statemen

Consolidated Financial Statement Details	12 Months Ended
	Dec. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidated Financial Statement Details	Consolidated Financial Statement Details Other Current Liabilities Included in other current liabilities as of December 30, 2017 and December 31, 2016 were the following: (i) accrued discounts, allowances, and customer rebates of $ 39.5 million and $ 40.4 million , respectively, (ii) current taxes payable of $ 9.2 million and $ 4.6 million , respectively, (iii) accrued interest of $5.9 million and $0.3 million , respectively, and (iv) current environmental liabilities of $4.3 million and $0.8 million , respectively. Other Income, Net (In thousands) 2017 2016 2015 Interest income $ 684 $ 1,185 $ 1,029 Other 1,117 798 1,205 Other income, net $ 1,801 $ 1,983 $ 2,234

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities The Company’s earnings and cash flows are subject to fluctuations due to changes in commodity prices, foreign currency exchange rates, and interest rates. The Company uses derivative instruments such as commodity futures contracts, foreign currency forward contracts, and interest rate swaps to manage these exposures. Commodity Futures Contracts Copper and brass represent the largest component of the Company’s variable costs of production. The cost of these materials is subject to global market fluctuations caused by factors beyond the Company’s control. The Company occasionally enters into forward fixed-price arrangements with certain customers; the risk of these arrangements is generally managed with commodity futures contracts. These futures contracts have been designated as cash flow hedges. At December 30, 2017 , the Company held open futures contracts to purchase approximately $ 19.6 million of copper over the next 12 months related to fixed price sales orders. The fair value of those futures contracts was a $ 1.0 million net gain position, which was determined by obtaining quoted market prices (level 1 within the fair value hierarchy). In the next twelve months, the Company will reclassify into earnings realized gains or losses relating to cash flow hedges. At December 30, 2017 , this amount was approximately $ 0.7 million of deferred net gains , net of tax. The Company may also enter into futures contracts to protect the value of inventory against market fluctuations. At December 30, 2017 , the Company held open futures contracts to sell approximately $ 85.3 million of copper over the next five months related to copper inventory. The fair value of those futures contracts was a $ 3.2 million net loss position, which was determined by obtaining quoted market prices (level 1 within the fair value hierarchy). The Company presents its derivative assets and liabilities in the Consolidated Balance Sheets on a net basis by counterparty. The following table summarizes the location and fair value of the derivative instruments and disaggregates the net derivative assets and liabilities into gross components on a contract-by-contract basis: Asset Derivatives Liability Derivatives Fair Value Fair Value (In thousands) Balance Sheet Location 2017 2016 Balance Sheet Location 2017 2016 Commodity contracts - gains Other current assets $ 1,014 $ 1,013 Other current liabilities $ 55 $ 564 Commodity contracts - losses Other current assets (5 ) (148 ) Other current liabilities (3,210 ) (920 ) Interest rate swap Other current assets — — Other current liabilities — (787 ) Total derivatives (1) $ 1,009 $ 865 $ (3,155 ) $ (1,143 ) (1) Does not include the impact of cash collateral provided to counterparties . The following tables summarize the effects of derivative instruments on the Consolidated Statements of Income: (In thousands) Location 2017 2016 Fair value hedges: Loss on commodity contracts (qualifying) Cost of goods sold $ (724 ) $ (420 ) Gain on hedged item - inventory Cost of goods sold 625 382 Undesignated derivatives: (Loss) gain on commodity contracts (nonqualifying) Cost of goods sold $ (6,078 ) $ 4,068 The following tables summarize amounts recognized in and reclassified from AOCI during the period: Year Ended December 30, 2017 (In thousands) (Loss) Gain Recognized in AOCI (Effective Portion), Net of Tax Classification Gains (Losses) Loss Reclassified from AOCI (Effective Portion), Net of Tax Cash flow hedges: Commodity contracts $ (574 ) Cost of goods sold $ 990 Interest rate swap — Interest expense 546 Other 185 Other — Total $ (389 ) Total $ 1,536 Derivative instruments and hedging activities (continued): Year Ended December 31, 2016 (In thousands) Gain (Loss) Recognized in AOCI (Effective Portion), Net of Tax Classification Gains (Losses) Loss Reclassified from AOCI (Effective Portion), Net of Tax Cash flow hedges: Commodity contracts $ 308 Cost of goods sold $ 1,078 Interest rate swap 305 Interest expense 231 Other (213 ) Other — Total $ 400 Total $ 1,309 The Company enters into futures and forward contracts that closely match the terms of the underlying transactions. As a result, the ineffective portion of the qualifying open hedge contracts through December 30, 2017 was not material to the Consolidated Statements of Income. The Company primarily enters into International Swaps and Derivatives Association master netting agreements with major financial institutions that permit the net settlement of amounts owed under their respective derivative contracts. Under these master netting agreements, net settlement generally permits the Company or the counterparty to determine the net amount payable for contracts due on the same date and in the same currency for similar types of derivative transactions. The master netting agreements generally also provide for net settlement of all outstanding contracts with the counterparty in the case of an event of default or a termination event. The Company does not offset fair value amounts for derivative instruments and fair value amounts recognized for the right to reclaim cash collateral. At December 30, 2017 and December 31, 2016 , the Company had recorded restricted cash in other current assets of $ 5.3 million and $ 1.4 million , respectively, as collateral related to open derivative contracts under the master netting arrangements.

Property, Plant, and Equipment,

Property, Plant, and Equipment, Net	12 Months Ended
	Dec. 30, 2017
Property, Plant and Equipment [Abstract]
Property, Plant, and Equipment, Net	Property, Plant, and Equipment, Net (In thousands) 2017 2016 Land and land improvements $ 18,740 $ 19,928 Buildings 144,527 144,914 Machinery and equipment 649,667 607,344 Construction in progress 9,274 30,344 822,208 802,530 Less accumulated depreciation (517,887 ) (507,299 ) Property, plant, and equipment, net $ 304,321 $ 295,231

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill The changes in the carrying amount of goodwill by segment were as follows: (In thousands) Piping Systems Industrial Metals Climate Total Goodwill $ 156,387 $ 8,854 $ 4,416 $ 169,657 Accumulated impairment charges (40,552 ) (8,853 ) — (49,405 ) Balance at December 26, 2015: 115,835 1 4,416 120,252 Additions (1) 4,601 — — 4,601 Currency translation (860 ) — — (860 ) Balance at December 31, 2016: 119,576 1 4,416 123,993 Additions (2) 3,852 — — 3,852 Currency translation 2,448 — — 2,448 Balance at December 30, 2017: Goodwill 166,428 8,854 4,416 179,698 Accumulated impairment charges (40,552 ) (8,853 ) — (49,405 ) Goodwill, net $ 125,876 $ 1 $ 4,416 $ 130,293 (1) Includes finalization of the purchase price allocation adjustment for Great Lakes of $4.1 million . (2) Includes finalization of the purchase price allocation adjustment for Jungwoo-Mueller of $0.2 million . Reporting units with recorded goodwill include DPS, B&K LLC, Great Lakes, Heatlink Group, European Operations, Jungwoo-Mueller, Westermeyer, and Turbotec . Several factors give rise to goodwill in the Company’s acquisitions, such as the expected benefit from synergies of the combination and the existing workforce of the acquired businesses. There were no impairment charges resulting from the 2017 , 2016 , or 2015 annual impairment tests as the estimated fair value of each of the reporting units exceeded its carrying value. Other Intangible Assets The carrying amount of intangible assets at December 30, 2017 was as follows: (In thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Customer relationships $ 36,518 $ (4,644 ) $ 31,874 Non-compete agreements 2,834 (1,497 ) 1,337 Patents and technology 7,673 (1,868 ) 5,805 Trade names and licenses 4,977 (1,575 ) 3,402 Other 213 (623 ) (410 ) Other intangible assets $ 52,215 $ (10,207 ) $ 42,008 The carrying amount of intangible assets at December 31, 2016 was as follows: (In thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Customer relationships $ 29,833 $ (2,845 ) $ 26,988 Non-compete agreements 5,926 (4,063 ) 1,863 Patents and technology 5,922 (1,179 ) 4,743 Trade names and licenses 4,087 (1,032 ) 3,055 Other 213 (694 ) (481 ) Other intangible assets $ 45,981 $ (9,813 ) $ 36,168 Amortization expense for intangible assets was $3.1 million in 2017 , $4.3 million in 2016 , and $4.1 million in 2015 . Future amortization expense is estimated as follows: (In thousands) Amount 2018 $ 3,338 2019 3,253 2020 3,017 2021 2,747 2022 2,851 Thereafter 26,802 Expected amortization expense $ 42,008

Investment in Unconsolidated Af

Investment in Unconsolidated Affiliates	12 Months Ended
	Dec. 30, 2017
Equity Method Investments and Joint Ventures [Abstract]
Investment in Unconsolidated Affiliates	Investment in Unconsolidated Affiliates The Company owns a 50 percent interest in an unconsolidated affiliate that acquired Tecumseh. The Company also owns a 50 percent interest in a second unconsolidated affiliate that provides financing to Tecumseh. Tecumseh is a global manufacturer of hermetically sealed compressors for residential and specialty air conditioning, household refrigerators and freezers, and commercial refrigeration applications, including air conditioning and refrigeration compressors, as well as condensing units, heat pumps, and complete refrigeration systems. The following tables present summarized financial information derived from the Company’s equity method investees’ combined consolidated financial statements, which are prepared in accordance with U.S. GAAP. (In thousands) 2017 2016 Current assets $ 246,127 $ 244,323 Noncurrent assets 139,200 130,400 Current liabilities 174,710 148,806 Noncurrent liabilities 58,334 71,681 Net sales $ 556,600 $ 579,400 Gross profit 75,600 79,600 Net (loss) income (4,153 ) 3,720 Included in the equity method investees’ net income for 2016 is a gain of $17.1 million that resulted from the allocation of the purchase price, which was finalized during Tecumseh’s quarter ended December 31, 2015. That gain was offset by restructuring and impairment charges of $5.3 million and net losses of $8.1 million . On December 30, 2015, the Company entered into a joint venture agreement with Cayan Ventures and Bahrain Mumtalakat Holding Company to build a copper tube mill in Bahrain. The business will operate and brand its products under the Mueller Industries family of brands. The Company has invested approximately $3.9 million of cash to date and will be the technical and marketing lead in return for 40 percent ownership in the joint venture.

New Markets Tax Credit Transact

New Markets Tax Credit Transactions	12 Months Ended
	Dec. 30, 2017
New Markets Tax Credit Transaction [Abstract]
New Markets Tax Credit Transactions	New Markets Tax Credit Transactions On October 18, 2016, the Company entered into a financing transaction with Wells Fargo Community Investment Holdings, LLC (Wells Fargo) related to an equipment modernization project at the Company’s copper tube and line sets production facilities in Fulton, MS. Wells Fargo made a capital contribution and the Company made a loan to MCTC Investment Fund, LLC (Investment Fund) under a qualified New Markets Tax Credit (NMTC) program. The NMTC program was provided for in the Community Renewal Tax Relief Act of 2000 (CRTR Act) and is intended to induce capital investment in qualified lower income communities. The CRTR Act permits taxpayers to claim credits against their Federal income taxes for up to 39 percent of qualified investments in the equity of community development entities (CDEs). CDEs are privately managed investment institutions that are certified to make qualified low-income community investments. In connection with the financing, the Company loaned $13.7 million aggregate principal amount of a one percent loan (Leverage Loan) due October 17, 2041 , to the Investment Fund. Additionally, Wells Fargo contributed $6.6 million to the Investment Fund, and as such, Wells Fargo is entitled to substantially all of the benefits derived from the NMTCs. The Investment Fund then contributed the proceeds to certain CDEs, which, in turn, loaned the funds on similar terms as the Leverage Loan to Mueller Copper Tube Company, Inc. (MCTC), an indirect, wholly-owned subsidiary of the Company. The proceeds of the loans from the CDEs, including loans representing the capital contribution made by Wells Fargo, net of syndication fees, are restricted for use on the modernization project. The NMTC is subject to 100 percent recapture for a period of seven years as provided in the Internal Revenue Code. The Company is required to comply with various regulations and contractual provisions that apply to the NMTC arrangement. Non-compliance with applicable requirements could result in projected tax benefits not being realized and, therefore, require the Company to indemnify Wells Fargo for any loss or recapture of NMTCs related to the financing until such time as the Company’s obligation to deliver tax benefits is relieved. The Company does not anticipate any credit recaptures will be required in connection with this arrangement. This transaction also includes a put/call provision whereby the Company may be obligated or entitled to repurchase Wells Fargo’s interest in the Investment Fund. The Company believes that Wells Fargo will exercise the put option in October 2023, at the end of the recapture period. The value attributed to the put/call is negligible. The Company has determined that the financing arrangement with the Investment Fund and CDEs is a variable interest entity (VIE), and that it is the primary beneficiary of the VIE. This conclusion was reached based on the following: • The ongoing activities of the VIE, collecting and remitting interest and fees, and NMTC compliance were all considered in the initial design and are not expected to significantly affect economic performance throughout the life of the VIE; • Contractual arrangements obligate the Company to comply with NMTC rules and regulations and provide various other guarantees to the Investment Fund and CDEs; • Wells Fargo lacks a material interest in the underling economics of the project; and • The Company is obligated to absorb losses of the VIE. Because the Company is the primary beneficiary of the VIE, it has been included in the Company’s Consolidated Financial Statements. Wells Fargo’s contribution of $ 6.6 million was initially recorded as restricted cash and its interest in the Investment Fund is included in other liabilities.

Debt

Debt	12 Months Ended
	Dec. 30, 2017
Debt Disclosure [Abstract]
Debt	Debt (In thousands) 2017 2016 Subordinated Debentures with interest at 6.00%, due 2027 $ 284,536 $ — Revolving Credit Facility with interest at 3.06%, due 2021 160,000 200,000 Jungwoo-Mueller credit facility with interest at 2.72%, due 2018 5,119 4,724 Jungwoo-Mueller credit facility with interest at 3.19%, due 2017 8,648 7,990 2001 Series IRB's with interest at 2.22%, due 2021 3,250 4,250 Mueller-Xingrong credit facility — 3,048 Other 4,694 8,309 466,247 228,321 Less debt issuance costs (1,175 ) (957 ) Less current portion of debt (16,480 ) (13,655 ) Long-term debt $ 448,592 $ 213,709 Subordinated Debentures On March 9, 2017, the Company distributed a special dividend of $3.00 in cash and $5.00 in principal amount of the Company’s 6% Subordinated Debentures (Debentures) due March 1, 2027 for each share of common stock outstanding. Interest on the Debentures is payable semiannually on September 1 and March 1 and commenced on September 1, 2017. At issuance, the Debentures were recorded at their estimated fair value. The fair value of the Debentures was estimated based on quoted market prices for the same or similar issues, the current rates offered to the Company for debt of the same remaining maturities, or the use of market standard models. The Debentures are subordinated to all other funded debt of the Company and are callable, in whole or in part, at any time at the option of the Company, subject to declining call premiums during the first five years. The Debentures also grant each holder the right to require the Company to repurchase such holder’s Debentures in the event of a change in control at declining repurchase premiums during the first five years. The Debentures may be redeemed, subject to the conditions set forth above, at the following redemption price (expressed as a percentage of principal amount) plus any accrued but unpaid interest to, but excluding, the redemption date: If redeemed during the 12-month period beginning March 9: Year Redemption Price 2017 106% 2018 105 2019 104 2020 103 2021 102 2022 and thereafter 100 The effect of the special dividend was a decrease in stockholders’ equity of approximately $458.7 million , an increase in long-term debt of approximately $284.5 million , and a decrease in cash of approximately $174.2 million . Revolving Credit Facility The Company’s Credit Agreement provides for an unsecured $350.0 million revolving credit facility (Revolving Credit Facility) that matures on December 6, 2021 . Borrowings under the Revolving Credit Facility bear interest, at the Company’s option, at LIBOR or Base Rate as defined by the Credit Agreement, plus a variable premium. LIBOR advances may be based upon the one, three, or six-month LIBOR. The variable premium is based upon the Company’s debt to total capitalization ratio, and can range from 112.5 to 162.5 basis points for LIBOR based loans and 12.5 to 62.5 basis points for Base Rate loans. At December 30, 2017 , the premium was 150.0 basis points for LIBOR loans and 50.0 basis points for Base Rate loans. Additionally, a commitment fee is payable quarterly on the total commitment less any outstanding loans or issued letters of credit, and varies from 15.0 to 30.0 basis points based upon the Company’s debt to total capitalization ratio. Availability of funds under the Revolving Credit Facility is reduced by the amount of certain outstanding letters of credit, which are used to secure the Company’s payment of insurance deductibles and certain retiree health benefits, totaling approximately $8.4 million at December 30, 2017 . Terms of the letters of credit are generally renewable annually. Jungwoo-Mueller Jungwoo-Mueller has several secured revolving credit arrangements with a total borrowing capacity of KRW 29.9 billion (or approximately $27.5 million ). Borrowings are secured by the real property and equipment of Jungwoo-Mueller. Covenants contained in the Company’s financing obligations require, among other things, the maintenance of minimum levels of tangible net worth and the satisfaction of certain minimum financial ratios. At December 30, 2017 , the Company was in compliance with all debt covenants. Aggregate annual maturities of the Company’s debt are as follows: (In thousands) Amount 2018 $ 16,480 2019 1,222 2020 1,222 2021 160,472 2022 222 Thereafter 286,629 Long-term debt $ 466,247 Net interest expense consisted of the following: (In thousands) 2017 2016 2015 Interest expense $ 19,716 $ 7,749 $ 8,335 Capitalized interest (214 ) (362 ) (668 ) $ 19,502 $ 7,387 $ 7,667 Interest paid in 2017 , 2016 , and 2015 was $13.8 million , $7.1 million , and $8.1 million , respectively.

Benefit Plans

Benefit Plans	12 Months Ended
	Dec. 30, 2017
Compensation and Retirement Disclosure [Abstract]
Benefit Plans	Benefit Plans Pension and Other Postretirement Plans The Company sponsors several qualified and nonqualified pension plans and other postretirement benefit plans for certain employees. The following tables provide a reconciliation of the changes in the plans’ benefit obligations and the fair value of the plans’ assets for 2017 and 2016 , and a statement of the plans’ aggregate funded status: Pension Benefits Other Benefits (In thousands) 2017 2016 2017 2016 Change in benefit obligation: Obligation at beginning of year $ 178,736 $ 192,761 $ 15,274 $ 15,843 Service cost 128 532 235 232 Interest cost 6,344 7,553 599 594 Actuarial loss (gain) 4,688 9,399 923 (249 ) Plan amendments — — — 43 Benefit payments (10,171 ) (17,572 ) (883 ) (1,023 ) Settlement charge — — (209 ) — Foreign currency translation adjustment 7,041 (13,937 ) 468 (166 ) Obligation at end of year 186,766 178,736 16,407 15,274 Change in fair value of plan assets: Fair value of plan assets at beginning of year 169,140 176,077 — — Actual return on plan assets 19,175 19,319 — — Employer contributions 2,271 2,377 883 1,023 Benefit payments (10,171 ) (17,572 ) (883 ) (1,023 ) Foreign currency translation adjustment 5,921 (11,061 ) — — Fair value of plan assets at end of year 186,336 169,140 — — Underfunded status at end of year $ (430 ) $ (9,596 ) $ (16,407 ) $ (15,274 ) During 2016 , the Company offered a lump sum window to certain inactive participants in one of its pension plans, resulting in incremental benefit payments of $7.0 million and a settlement charge of $1.2 million . The following represents amounts recognized in AOCI (before the effect of income taxes): Pension Benefits Other Benefits (In thousands) 2017 2016 2017 2016 Unrecognized net actuarial loss $ 34,627 $ 39,986 $ 1,540 $ 614 Unrecognized prior service credit — — (7,289 ) (8,180 ) The Company sponsors one pension plan in the U.K. which comprised 44 and 42 percent of the above benefit obligation at December 30, 2017 and December 31, 2016 , respectively, and 39 and 36 percent of the above plan assets at December 30, 2017 and December 31, 2016 , respectively. As of December 30, 2017 , $1.5 million of the actuarial net loss and $0.9 million of the prior service credit will, through amortization, be recognized as components of net periodic benefit cost in 2018 . The aggregate status of all overfunded plans is recognized as an asset and the aggregate status of all underfunded plans is recognized as a liability in the Consolidated Balance Sheets. The amounts recognized as a liability are classified as current or long-term on a plan-by-plan basis. Liabilities are classified as current to the extent the actuarial present value of benefits payable within the next 12 months exceeds the fair value of plan assets, with all remaining amounts classified as long-term. As of December 30, 2017 and December 31, 2016 , the total funded status of the plans recognized in the Consolidated Balance Sheets was as follows: Pension Benefits Other Benefits (In thousands) 2017 2016 2017 2016 Long-term asset $ 9,894 $ 4,442 $ — $ — Current liability — — (1,070 ) (1,128 ) Long-term liability (10,324 ) (14,038 ) (15,337 ) (14,146 ) Total underfunded status $ (430 ) $ (9,596 ) $ (16,407 ) $ (15,274 ) The components of net periodic benefit cost are as follows: (In thousands) 2017 2016 2015 Pension benefits: Service cost $ 128 $ 532 $ 803 Interest cost 6,344 7,553 8,032 Expected return on plan assets (9,374 ) (9,615 ) (10,289 ) Amortization of net loss 2,206 2,898 2,710 Settlement charge — 1,214 — Net periodic benefit (income) cost $ (696 ) $ 2,582 $ 1,256 Other benefits: Service cost $ 235 $ 232 $ 363 Interest cost 599 594 1,005 Amortization of prior service (credit) cost (901 ) (896 ) 6 Amortization of net gain (42 ) (60 ) (28 ) Settlement charge 17 — — Net periodic benefit (income) cost $ (92 ) $ (130 ) $ 1,346 The weighted average assumptions used in the measurement of the Company’s benefit obligations are as follows: Pension Benefits Other Benefits 2017 2016 2017 2016 Discount rate 3.22 % 3.61 % 3.89 % 4.21 % Expected long-term return on plan assets 5.27 % 5.56 % N/A N/A Rate of compensation increases N/A N/A 5.00 % 5.00 % Rate of inflation 3.30 % 3.30 % N/A N/A The weighted average assumptions used in the measurement of the Company’s net periodic benefit cost are as follows: Pension Benefits Other Benefits 2017 2016 2015 2017 2016 2015 Discount rate 3.61 % 4.02 % 4.03 % 4.21 % 4.25 % 4.33 % Expected long-term return on plan assets 5.56 % 5.59 % 5.58 % N/A N/A N/A Rate of compensation increases N/A N/A N/A 5.00 % 5.00 % 5.00 % Rate of inflation 3.30 % 3.20 % 3.10 % N/A N/A N/A The Company’s Mexican postretirement plans use the rate of compensation increase in the benefit formulas. Past service in the U.K. pension plan will be adjusted for the effects of inflation. All other pension and postretirement plans use benefit formulas based on length of service. The annual assumed rate of increase in the per capita cost of covered benefits (i.e., health care cost trend rate) is assumed to range from 6.6 to 10.1 percent for 2018 , gradually decrease to 3.0 percent through 2036 , and remain at that level thereafter. The health care cost trend rate assumption does not have a significant effect on the amounts reported. Pension Assets The weighted average asset allocation of the Company’s pension fund assets are as follows: Pension Plan Assets Asset category 2017 2016 Equity securities (includes equity mutual funds) 46 % 47 % Fixed income securities (includes fixed income mutual funds) 48 48 Cash and equivalents (includes money market funds) 3 3 Alternative investments 3 2 Total 100 % 100 % At December 30, 2017 , the long-term target allocation, by asset category, of assets of the Company’s defined benefit pension plans was: (i) fixed income securities – at least 60 percent ; (ii) equity securities, including equity index funds – not more than 30 percent ; and (iii) alternative investments – not more than 5 percent . The pension plan obligations are long-term and, accordingly, the plan assets are invested for the long-term. Plan assets are monitored periodically. Based upon results, investment managers and/or asset classes are redeployed when considered necessary. None of the plans’ assets are expected to be returned to the Company during the next fiscal year. The assets of the plans do not include investments in securities issued by the Company. The estimated rates of return on plan assets are the expected future long-term rates of earnings on plan assets and are forward-looking assumptions that materially affect pension cost. Establishing the expected future rates of return on pension assets is a judgmental matter. The Company reviews the expected long-term rates of return on an annual basis and revises as appropriate. The expected long-term rate of return on plan assets was 5.27 percent for 2017 and 5.56 percent in 2016 . The Company’s investments for its pension plans are reported at fair value. The following methods and assumptions were used to estimate the fair value of the Company’s plan asset investments: Cash and money market funds – Valued at cost, which approximates fair value. Common stock – Valued at the closing price reported on the active market on which the individual securities are traded. Mutual funds – Valued at the net asset value of shares held by the plans at December 30, 2017 and December 31, 2016 , respectively, based upon quoted market prices. Limited partnerships – Limited partnerships include investments in various Cayman Island multi-strategy hedge funds. The plans’ investments in limited partnerships are valued at the estimated fair value of the class shares owned by the plans based upon the equity in the estimated fair value of those shares. The estimated fair values of the limited partnerships are determined by the investment managers. In determining fair value, the investment managers of the limited partnerships utilize the estimated net asset valuations of the underlying investment entities. The underlying investment entities value securities and other financial instruments on a mark-to-market or estimated fair value basis. The estimated fair value is determined by the investment managers based upon, among other things, the type of investments, purchase price, marketability, current financial condition, operating results, and other information. The estimated fair values of substantially all of the investments of the underlying investment entities, which may include securities for which prices are not readily available, are determined by the investment managers or management of the respective underlying investment entities and may not reflect amounts that could be realized upon immediate sale. Accordingly, the estimated fair values may differ significantly from the values that would have been used had a ready market existed for these investments. The following table sets forth by level, within the fair value hierarchy, the assets of the plans at fair value: Fair Value Measurements at December 30, 2017 (In thousands) Level 1 Level 2 Level 3 Total Cash and money market funds $ 5,364 $ — $ — $ 5,364 Common stock (1) 11,113 — — 11,113 Mutual funds (2) 8,412 156,442 — 164,854 Limited partnerships — — 5,005 5,005 Total $ 24,889 $ 156,442 $ 5,005 $ 186,336 Fair Value Measurements at December 31, 2016 (In thousands) Level 1 Level 2 Level 3 Total Cash and money market funds $ 4,245 $ — $ — $ 4,245 Common stock (3) 18,601 — — 18,601 Mutual funds (4) 5,572 136,027 — 141,599 Limited partnerships — — 4,695 4,695 Total $ 28,418 $ 136,027 $ 4,695 $ 169,140 (1) Approximately 91 percent of common stock represents investments in U.S. companies primarily in the health care, utilities, financials, consumer staples, industrials, and information technology sectors. All investments in common stock are listed on U.S. stock exchanges. (2) Approximately 66 percent of mutual funds are actively managed funds and approximately 34 percent of mutual funds are index funds. Additionally, five percent of the mutual funds’ assets are invested in U.S. equities, 41 percent in non-U.S. equities, 52 percent in U.S. fixed income securities, and two percent in non-U.S. fixed income securities. (3) Approximately 90 percent of common stock represents investments in U.S. companies primarily in the health care, utilities, financials, consumer staples, industrials, and information technology sectors. All investments in common stock are listed on U.S. stock exchanges. (4) Approximately 68 percent of mutual funds are actively managed funds and approximately 32 percent of mutual funds are index funds. Additionally, five percent of the mutual funds’ assets are invested in U.S. equities, 38 percent in non-U.S. equities, 54 percent in U.S. fixed income securities, and three percent in non-U.S. fixed income securities. The table below reflects the changes in the assets of the plan measured at fair value on a recurring basis using significant unobservable inputs (level 3 of fair value hierarchy) during the year ended December 30, 2017 : (In thousands) Limited Partnerships Balance, December 31, 2016 $ 4,695 Redemptions (283 ) Subscriptions 273 Net appreciation in fair value 320 Balance, December 30, 2017 $ 5,005 Contributions and Benefit Payments The Company expects to contribute approximately $1.0 million to its pension plans and $1.2 million to its other postretirement benefit plans in 2017. The Company expects future benefits to be paid from the plans as follows: (In thousands) Pension Benefits Other Benefits 2018 $ 10,423 $ 1,177 2019 10,398 1,056 2020 10,329 1,277 2021 10,246 1,129 2022 10,182 1,157 2023-2027 49,965 6,154 Total $ 101,543 $ 11,950 Multiemployer Plan The Company contributes to the IAM National Pension Fund, National Pension Plan (IAM Plan), a multiemployer defined benefit plan. Participation in the IAM Plan was negotiated under the terms of two collective bargaining agreements in Port Huron, Michigan, the Local 218 IAM and Local 44 UAW that expire on May 5, 2019 and July 21, 2019 , respectively. The Employer Identification Number for this plan is 51-6031295. The risks of participating in multiemployer plans are different from single-employer plans in the following aspects: (i) assets contributed to the multiemployer plan by one employer may be used to provide benefits to employees of other participating employers; (ii) if a participating employer stops contributing to the plan, the underfunded obligations of the plan may be borne by the remaining participating employers; (iii) if the Company chooses to stop participating in the plan, the Company may be required to pay the plan an amount based on the underfunded status of the plan, referred to as a withdrawal liability. The Company makes contributions to the IAM Plan trusts that cover certain union employees; contributions by employees are not permitted. Contributions to the IAM Plan were approximately $1.1 million each year in 2017 , 2016 , and 2015 . The Company’s contributions are less than five percent of total employer contributions made to the IAM Plan indicated in the most recently filed Form 5500. Under the Pension Protection Act of 2006, the IAM Plan’s actuary must certify the plan’s zone status annually. Plans in the red zone are generally less than 65 percent funded, plans in the yellow zone are less than 80 percent funded, and plans in the green zone are at least 80 percent funded. If a plan is determined to be in endangered status, red zone or yellow zone, the plan’s trustees must develop a formal plan of corrective action, a Financial Improvement Plan and/or a Rehabilitation Plan. For 2017 and 2016 the IAM Plan was determined to have green zone status; therefore, no formal plan of corrective action is either pending or has been implemented. 401(k) Plans The Company sponsors voluntary employee savings plans that qualify under Section 401(k) of the Internal Revenue Code of 1986. Compensation expense for the Company’s matching contribution to the 401(k) plans was $5.1 million in 2017 , $5.2 million in 2016 , and $4.2 million in 2015 . The Company match is a cash contribution. Participants direct the investment of their account balances by allocating among a range of asset classes including mutual funds (equity, fixed income, and balanced funds) and money market funds. The plans do not allow direct investment in securities issued by the Company. UMWA Benefit Plans In October 1992, the Coal Industry Retiree Health Benefit Act of 1992 (1992 Act) was enacted. The 1992 Act mandates a method of providing for postretirement benefits to the United Mine Workers of America (UMWA) current and retired employees, including some retirees who were never employed by the Company. In October 1993, beneficiaries were assigned to the Company and the Company began its mandated contributions to the UMWA Combined Benefit Fund, a multiemployer trust. Beginning in 1994, the Company was required to make contributions for assigned beneficiaries under an additional multiemployer trust created by the 1992 Act, the UMWA 1992 Benefit Plan. The ultimate amount of the Company’s liability under the 1992 Act will vary due to factors which include, among other things, the validity, interpretation, and regulation of the 1992 Act, its joint and several obligation, the number of valid beneficiaries assigned, and the extent to which funding for this obligation will be satisfied by transfers of excess assets from the 1950 UMWA pension plan and transfers from the Abandoned Mine Reclamation Fund. Contributions to the plan were $182 thousand , $197 thousand , and $214 thousand for the years ended 2017 , 2016 , and 2015 , respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Environmental The Company is subject to federal, state, local, and foreign environmental laws and regulations. For all properties, the Company has provided and charged to expense $7.5 million in 2017 , $0.9 million in 2016 , and $0.1 million in 2015 for pending environmental matters. Environmental reserves totaled $28.0 million at December 30, 2017 and $21.9 million at December 31, 2016 . As of December 30, 2017 , the Company expects to spend $4.3 million in 2018 , $2.2 million in 2019 , $2.1 million in 2020 , $0.6 million in 2021 , $0.6 million in 2022 , and $18.2 million thereafter for ongoing projects. Non-operating Properties Southeast Kansas Sites The Kansas Department of Health and Environment (KDHE) has contacted the Company regarding environmental contamination at three former smelter sites in Kansas (Altoona, East La Harpe, and Lanyon). The Company is not a successor to the companies that operated these smelter sites, but is exploring possible settlement with KDHE and other potentially responsible parties (PRP) in order to avoid litigation. Another PRP conducted a site investigation of the Altoona site under a consent decree with KDHE and submitted a removal site evaluation report recommending a remedy. The remedial design plan, which covers both on-site and certain off-site cleanup costs, was approved by the KDHE in 2016. At the East La Harpe site, the Company and two other PRPs conducted a site study evaluation under KDHE supervision and prepared a site cleanup plan approved by KDHE. In 2016, the corporate parent of a third party that the Company understands may owe indemnification obligations to one of the other PRPs in connection with the East La Harpe site filed for protection under Chapter 11 of the U.S. Bankruptcy Code. KDHE has extended the deadline for the PRPs to develop a repository design plan to allow for wetlands permitting to take place. With respect to the Lanyon Site, in 2016, the Company received a general notice letter from the United States Environmental Protection Agency (EPA) asserting that the Company is a PRP, which the Company has denied. The Company’s reserve for its proportionate share of the remediation costs associated with the Southeast Kansas sites is $5.6 million . Shasta Area Mine Sites Mining Remedial Recovery Company (MRRC), a wholly owned subsidiary, owns certain inactive mines in Shasta County, California. MRRC has continued a program, begun in the late 1980s, of implementing various remedial measures, including sealing mine portals with concrete plugs in portals that were discharging water. The sealing program achieved significant reductions in the metal load in discharges from these adits; however, additional reductions are required pursuant to an order issued by the California Regional Water Quality Control Board (QCB). In response to a 1996 QCB Order, MRRC completed a feasibility study in 1997 describing measures designed to mitigate the effects of acid rock drainage. In December 1998, the QCB modified the 1996 order extending MRRC’s time to comply with water quality standards. In September 2002, the QCB adopted a new order requiring MRRC to adopt Best Management Practices (BMP) to control discharges of acid mine drainage, and again extended the time to comply with water quality standards until September 2007. During that time, implementation of BMP further reduced impacts of acid rock drainage; however, full compliance has not been achieved. The QCB is presently renewing MRRC’s discharge permit and will concurrently issue a new order. It is expected that the new 10 -year permit will include an order requiring continued implementation of BMP through 2025 to address residual discharges of acid rock drainage. At this site, MRRC spent approximately $1.2 million from 2015 through 2017 for remediation, and currently estimates that it will spend between approximately $12.8 million and $17.6 million over the next 30 years. Lead Refinery Site U.S.S. Lead Refinery, Inc. (Lead Refinery), a non-operating wholly owned subsidiary of MRRC, has conducted corrective action and interim remedial activities (collectively, Site Activities) at Lead Refinery’s East Chicago, Indiana site pursuant to the Resource Conservation and Recovery Act since December 1996. Although the Site Activities have been substantially concluded, Lead Refinery is required to perform monitoring and maintenance-related activities pursuant to a post-closure permit issued by the Indiana Department of Environmental Management effective as of March 2, 2013. Lead Refinery spent approximately $0.6 million from 2015 through 2017 with respect to this site. Approximate costs to comply with the post-closure permit, including associated general and administrative costs, are estimated at between $1.8 million and $3.0 million over the next 19 years. On April 9, 2009, pursuant to the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), the U.S. Environmental Protection Agency (EPA) added the Lead Refinery site and surrounding properties to the National Priorities List (NPL). On July 17, 2009, Lead Refinery received a written notice from the EPA indicating that it may be a PRP under CERCLA due to the release or threat of release of hazardous substances including lead into properties surrounding the Lead Refinery NPL site. The EPA identified two other PRPs in connection with that matter. In November 2012, the EPA adopted a remedy for the surrounding properties and in September 2014, the EPA announced that it had entered into a settlement with the two other PRPs whereby they will pay approximately $26.0 million to fund the cleanup of approximately 300 properties surrounding the Lead Refinery NPL site (zones 1 and 3 of operable unit 1) and perform certain remedial action tasks. On November 8, 2016, the Company, its subsidiary Arava Natural Resources Company, Inc. (Arava), and Arava’s subsidiary MRRC each received general notice letters from the EPA asserting that they may be PRPs in connection with the Lead Refinery NPL site. The Company, Arava, and MRRC have denied liability for any remedial action and response costs associated with the Lead Refinery NPL site. In June 2017, the EPA requested that Lead Refinery conduct, and the Company fund, a remedial investigation and feasibility study of operable unit 2 of the Lead Refinery NPL site pursuant to a proposed administrative settlement agreement and order on consent. The Company and Lead Refinery entered into that agreement in September 2017. The Company will make a capital contribution to Lead Refinery to conduct the remedial investigation and feasibility study with respect to operable unit 2 and provide a financial guarantee in the amount of $1.0 million . The EPA has also asserted its position that Mueller is a responsible party for the Lead Refinery NPL site, and accordingly is responsible for a share of remedial action and response costs at the site and in the adjacent residential area. In January 2018, the EPA issued two unilateral administrative orders (UAOs) directing the Company, Lead Refinery, and four other PRPs to conduct soil and interior remediation of certain residences at the Lead Refinery NPL site (zones 2 and 3 of operable unit 1). The Company and Lead Refinery have reached agreement with the four other PRPs to implement these two UAOs, with the Company agreeing to pay, on an interim basis, (i) an estimated $4.5 million (subject to potential change through a future reallocation process) of the approximately $25.0 million the PRPs currently estimate it will cost to implement the UAOs, which estimate is subject to change, and (ii) $2.0 million relating to past costs incurred by other PRPs for work conducted at the site. These amounts are included in the Company’s reserve for environmental liabilities as of December 30, 2017 . The Company disputes that it was properly named in the UAOs, and has reserved its rights to petition the EPA for reimbursement of any costs incurred to comply with the UAOs upon the completion of the work required therein. In October 2017, a group of private plaintiffs sued the Company, Arava, MRRC, and Lead Refinery, along with other defendants, in a private tort action relating to the site. At this juncture, the Company is unable to determine the likelihood of a material adverse outcome or the amount or range of a potential loss in excess of the current reserve with respect to any remedial action or litigation relating to the Lead Refinery NPL site, either at Lead Refinery’s former operating site (operable unit 2) or the adjacent residential area (operable unit 1). Bonita Peak Mining District Following an August 2015 spill from the Gold King Mine into the Animas River near Silverton, Colorado, the EPA listed the Bonita Peak Mining District on the NPL. Said listing was finalized in September 2016. The Bonita Peak Mining District encompasses 48 mining sites within the Animas River watershed, including the Sunnyside Mine, the American Tunnel, and the Sunbank Group. On or about July 25, 2017, Washington Mining Company (Washington Mining) (a wholly-owned subsidiary of the Company’s wholly-owned subsidiary, Arava), received a general notice letter from the EPA stating that Washington Mining may be a PRP under CERCLA in connection with the Bonita Peak Mining District site and therefore responsible for the remediation of certain portions of the site, along with related costs incurred by the EPA. Shortly thereafter, the Company received a substantively identical letter asserting that it may be a PRP at the Site and similarly responsible for the cleanup of certain portions of the site. The general notice letters identify one other PRP at the site, and do not require specific action by Washington Mining or the Company at this time. At this juncture, the Company is unable to determine the likelihood of a materially adverse outcome or the amount or range of a potential loss with respect to any remedial action related to the Bonita Peak Mining District NPL site. Operating Properties Mueller Copper Tube Products, Inc. In 1999, Mueller Copper Tube Products, Inc. (MCTP), a wholly owned subsidiary, commenced a cleanup and remediation of soil and groundwater at its Wynne, Arkansas plant to remove trichloroethylene, a cleaning solvent formerly used by MCTP. On August 30, 2000, MCTP received approval of its Final Comprehensive Investigation Report and Storm Water Drainage Investigation Report addressing the treatment of soils and groundwater from the Arkansas Department of Environmental Quality (ADEQ). The Company established a reserve for this project in connection with the acquisition of MCTP in 1998. Effective November 17, 2008, MCTP entered into a Settlement Agreement and Administrative Order by Consent to submit a Supplemental Investigation Work Plan (SIWP) and subsequent Final Remediation Work Plan (RWP) for the site. By letter dated January 20, 2010, ADEQ approved the SIWP as submitted, with changes acceptable to the Company. On December 16, 2011, MCTP entered into an amended Administrative Order by Consent to prepare and implement a revised RWP regarding final remediation for the Site. The remediation system was activated in February 2014. Costs to implement the work plans, including associated general and administrative costs, are estimated to approximate $0.8 million to $1.2 million over the next eight years. United States Department of Commerce Antidumping Review On December 24, 2008, the Department of Commerce (DOC) initiated an antidumping administrative review of the antidumping duty order covering circular welded non-alloy steel pipe and tube from Mexico for the November 1, 2007 through October 31, 2008 period of review. The DOC selected Mueller Comercial as a respondent in the review. On April 19, 2010, the DOC published the final results of the review and assigned Mueller Comercial an antidumping duty rate of 48.33 percent . On May 25, 2010, the Company appealed the final results to the U.S. Court of International Trade (CIT). On December 16, 2011, the CIT issued a decision remanding the Department’s final results. While the matter was still pending, the Company and the United States reached an agreement to settle the appeal. Subject to the conditions of the agreement, the Company anticipated that certain of its subsidiaries would incur antidumping duties on subject imports made during the period of review and, as such, established a reserve for this matter. After the lapse of the statutory period of time during which U.S. Customs and Border Protection (CBP) was required, but failed, to liquidate the entries at the settled rate, the Company released the reserve. Between October 30, 2015 and November 27, 2015, CBP sent a series of invoices to Southland Pipe Nipples Co., Inc. (Southland), requesting payment of approximately $3.0 million in duties and interest in connection with 795 import entries made during the November 1, 2007 through October 31, 2008 period. On January 26, 2016 and January 27, 2016, Southland filed protests with CBP in connection with these invoices, noting that CBP’s asserted claims were not made in accordance with applicable law, including statutory provisions governing deemed liquidation. The Company believes in the merits of the legal objections raised in Southland’s protests, and CBP’s response to Southland’s protests is currently pending. Given the procedural posture and issues raised by this legal dispute, the Company cannot estimate the amount of potential duty liability, if any, that may result from CBP’s asserted claims. Equal Employment Opportunity Commission Matter On October 5, 2016, the Company received a demand letter from the Los Angeles District Office of the United States Equal Employment Opportunity Commission (EEOC). The EEOC alleges that between May 2011 and April 2015, various Company employees were terminated in violation of the Americans with Disabilities Act, and that certain of the Company’s employee leave and attendance policies were discriminatory in nature. On that basis, the EEOC’s letter includes a demand for monetary relief on behalf of an identified class of 20 individuals, and an unidentified class of 150 individuals, in addition to injunctive relief. The Company believes the EEOC’s allegations are without merit. Notwithstanding the Company’s position, in consultation with its liability insurers, the Company entered into a conciliation process with the EEOC for purposes of resolving the claims. On April 12, 2017, the Company received a letter from the EEOC stating that the conciliation process had concluded without a resolution of the claims, and that the matter would be referred to its Legal Department for potential litigation. The Company and the EEOC have since engaged in mediation efforts. Due to the procedural stage of this matter, the Company is unable to determine the likelihood of a material adverse outcome in this matter, or the amount or range of a potential loss in excess of any available insurance coverage. Leases The Company leases certain facilities, vehicles, and equipment under operating leases expiring on various dates through 2033 . The lease payments under these agreements aggregate to approximately $7.0 million in 2018 , $5.2 million in 2019 , $4.4 million in 2020 , $3.5 million in 2021 , $3.1 million in 2022 , and $17.3 million thereafter. Total lease expense amounted to $11.9 million in 2017 , $11.6 million in 2016 , and $9.7 million in 2015 . Other The Company is involved in certain litigation as a result of claims that arose in the ordinary course of business, which management believes will not have a material adverse effect on the Company’s financial position, results of operations, or cash flows. It may also realize the benefit of certain legal claims and litigation in the future; these gain contingencies are not recognized in the Consolidated Financial Statements.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The components of income before income taxes were taxed under the following jurisdictions: (In thousands) 2017 2016 2015 Domestic $ 76,876 $ 103,576 $ 121,614 Foreign 50,096 42,454 10,175 Income before income taxes $ 126,972 $ 146,030 $ 131,789 Income tax expense consists of the following: (In thousands) 2017 2016 2015 Current tax expense: Federal $ 28,584 $ 32,262 $ 50,272 Foreign 10,219 5,667 4,042 State and local 2,241 3,210 4,886 Current tax expense 41,044 41,139 59,200 Deferred tax (benefit) expense: Federal (1,764 ) 2,004 (13,739 ) Foreign 1,118 5,099 (1,180 ) State and local (2,514 ) (105 ) (899 ) Deferred tax (benefit) expense (3,160 ) 6,998 (15,818 ) Income tax expense $ 37,884 $ 48,137 $ 43,382 The difference between the reported income tax expense and a tax determined by applying the applicable U.S. federal statutory income tax rate to income before income taxes is reconciled as follows: (In thousands) 2017 2016 2015 Expected income tax expense $ 44,440 $ 51,110 $ 46,126 State and local income tax, net of federal benefit 1,135 1,982 2,673 Effect of foreign statutory rate different from U.S. and other foreign adjustments (6,026 ) (4,092 ) (654 ) U.S. production activities deduction (1,575 ) (3,063 ) (3,500 ) Goodwill disposition — — 646 Investment in unconsolidated affiliates 216 1,030 — Permanent adjustment to deferred tax liabilities — — (4,218 ) Benefit of stock-based compensation deductions (2,160 ) (656 ) — Effect of tax on accumulated foreign earnings 12,893 — — Effect of tax rate change on net deferred tax liability balance (12,067 ) — — Other, net 1,028 1,826 2,309 Income tax expense $ 37,884 $ 48,137 $ 43,382 The Tax Cuts and Jobs Act (the Act) was enacted on December 22, 2017. The Act reduces the U.S. federal corporate tax rate from 35 percent to 21 percent, requires companies to pay a one-time transition tax on the accumulated earnings of certain foreign subsidiaries, and creates new taxes on certain foreign-sourced earnings. At December 30, 2017 , the Company has not completed its accounting for the tax effects of enactment of the Act. However, the Company has made a reasonable estimate of the one-time transition tax on accumulated foreign earnings as well as the impact of the Act on its existing deferred tax balances. The one-time transition tax is based on the Company’s total post-1986 earnings and profits (E&P) for which the accrual of U.S. income taxes has previously been deferred. The Company recorded a provisional amount for its one-time transition tax liability, resulting in an increase in income tax expense of $12.9 million , or 22 cents per diluted share. The Company has not yet completed its calculation of the total post-1986 foreign E&P for these foreign subsidiaries. Further, the transition tax is impacted in part by the amount of those earnings held in cash and other specified assets. Accordingly, the Company’s estimate of the one-time transition tax may change when it finalizes the calculation of post-1986 foreign E&P previously deferred from U.S. federal taxation and finalizes the amounts held in cash or other specified assets. Consistent with prior years, the Company continues to assert that the earnings subject to the transition tax are permanently reinvested. Accordingly, no additional income taxes have been provided for any additional outside basis differences that may exist with respect to these entities or any taxes that may be due upon the repatriation of these earnings. Determining the amount of unrecognized deferred tax liability related to any additional outside basis difference in these entities (i.e., basis differences other than those subject to the one-time transition tax) is not practicable due to the complexities of the hypothetical calculation in determining residual taxes on undistributed earnings, including the availability of foreign tax credits, applicability of any additional local withholding tax, and other indirect tax consequences that may arise due to the distribution of these earnings. The Company remeasured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21 percent. However, the Company is still analyzing certain aspects of the Act and refining its calculations, which could potentially affect the measurement of these balances. The provisional amount recorded related to the remeasurement of the deferred tax balance was an income tax benefit of $12.1 million , or 21 cents per diluted share. The global intangible low-taxed income (GILTI) provisions of the Act impose a tax on the income of certain foreign subsidiaries in excess of a specified return on tangible assets used by the foreign companies. The FASB Staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to either recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or provide for the tax expense related to GILTI in the year the tax is incurred. Given the complexity of the GILTI provisions, the Company is still evaluating the effects of these provisions and has not yet determined the new accounting policy. Accordingly, the Company is unable to make a reasonable estimate and has not reflected any adjustments related to GILTI in its Consolidated Financial Statements. During 2015 , the Company had an adjustment to a deferred tax liability of $4.2 million , or seven cents per diluted share, resulting from the acquisition of a foreign subsidiary. The Company includes interest and penalties related to income tax matters as a component of income tax expense. The income tax expense related to penalties and interest was immaterial in 2017 , 2016 , and 2015 . The Internal Revenue Service completed its audit of the Company’s 2013 tax return during 2016, the results of which were immaterial to the Consolidated Financial Statements. The Company is currently under audit in various other jurisdictions. The statute of limitations is still open for the Company’s federal tax return and most state income tax returns for 2014 and all subsequent years. The statutes of limitations for certain state and foreign returns are also open for some earlier tax years due to differing statute periods. While the Company believes that it is adequately reserved for possible audit adjustments, the final resolution of these examinations cannot be determined with certainty and could result in final settlements that differ from current estimates. The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities are presented below: (In thousands) 2017 2016 Deferred tax assets: Inventories $ 10,598 $ 15,483 Other postretirement benefits and accrued items 9,239 13,180 Other reserves 9,029 9,821 Federal and foreign tax attributes 11,936 5,813 State tax attributes, net of federal benefit 29,720 22,572 Stock-based compensation 2,102 2,416 Basis difference in unconsolidated affiliates — 211 Total deferred tax assets 72,624 69,496 Less valuation allowance (30,316 ) (18,681 ) Deferred tax assets, net of valuation allowance 42,308 50,815 Deferred tax liabilities: Property, plant, and equipment 43,972 52,319 Pension 3,841 4,633 Basis difference in unconsolidated affiliates 203 — Total deferred tax liabilities 48,016 56,952 Net deferred tax liabilities $ (5,708 ) $ (6,137 ) As of December 30, 2017 , after consideration of the federal impact, the Company had state income tax credit carryforwards of $4.5 million , all of which expire by 2020, and other state income tax credit carryforwards of $12.6 million with unlimited lives. The Company had state net operating loss (NOL) carryforwards with potential tax benefits of $13.5 million expiring between 2019 and 2032. The state tax credit and NOL carryforwards are offset by valuation allowances totaling $17.6 million . As of December 30, 2017 , the Company had foreign tax credits with potential tax benefits of $5.1 million , which were fully offset by a valuation allowance. As of December 30, 2017 , the Company had foreign tax attributes with potential tax benefits of $5.9 million which have an unlimited life. These attributes were fully offset by a valuation allowance. Income taxes paid were approximately $42.5 million in 2017 , $40.1 million in 2016 , and $49.9 million in 2015 .

Equity

Equity	12 Months Ended
	Dec. 30, 2017
Equity [Abstract]
Equity	Equity The Company’s Board of Directors has extended, until August 2018 , its authorization to repurchase up to 20 million shares of the Company’s common stock through open market transactions or through privately negotiated transactions. The Company has no obligation to purchase any shares and may cancel, suspend, or extend the time period for the purchase of shares at any time. Any purchases will be funded primarily through existing cash and cash from operations. The Company may hold any shares purchased in treasury or use a portion of the repurchased shares for its stock-based compensation plans, as well as for other corporate purposes. From its initial authorization in 1999 through December 30, 2017 , the Company has repurchased approximately 4.7 million shares under this authorization.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation The Company has in effect stock incentive plans under which stock-based awards have been granted to certain employees and members of its Board of Directors. Under these existing plans, the Company may grant options to purchase shares of common stock at prices not less than the fair market value of the stock on the date of grant, as well as restricted stock awards. Generally, the awards vest within five years from the date of grant. Any unexercised options expire after not more than ten years . During the years ended December 30, 2017 , December 31, 2016 , and December 26, 2015 , the Company recognized stock-based compensation, as a component of selling, general, and administrative expense, in its Consolidated Statements of Income of $7.5 million , $6.4 million , and $6.2 million , respectively. Stock Options The fair value of each option is estimated as a single award and amortized into compensation expense on a straight-line or accrual basis over its vesting period based on its vesting schedule. The weighted average grant-date fair value of options granted during 2017 , 2016 , and 2015 was $9.38 , $7.87 , and $7.58 , respectively. The Company estimates the fair value of all stock option awards as of the grant date by applying the Black-Scholes-Merton option pricing model. The use of this valuation model in the determination of compensation expense involves certain assumptions that are judgmental and/or highly sensitive including the expected life of the option, stock price volatility, risk-free interest rate, and dividend yield. Additionally, forfeitures are not estimated at the time of valuation; they are recognized as they occur. The weighted average of key assumptions used in determining the fair value of options granted and a discussion of the methodology used to develop each assumption are as follows: 2017 2016 2015 Expected term 7.7 years 6.7 years 5.5 years Expected price volatility 28.9 % 25.6 % 26.2 % Risk-free interest rate 2.1 % 1.6 % 1.7 % Dividend yield 1.3 % 1.0 % 0.9 % Expected term – This is the period of time estimated based on historical experience over which the options granted are expected to remain outstanding. An increase in the expected term will increase compensation expense. Expected price volatility – This is a measure of the amount by which a price has fluctuated or is expected to fluctuate. The Company uses actual historical changes in the market value of its stock to calculate the volatility assumption. Daily market value changes from the date of grant over a past period representative of the expected term of the options are used. An increase in the expected price volatility rate will increase compensation expense. Risk-free interest rate – This is the U.S. Treasury rate for the week of the grant, having a term representative of the expected term of the options. An increase in the risk-free rate will increase compensation expense. Dividend yield – This rate is the annual dividends per share as a percentage of the Company’s stock price. An increase in the dividend yield will decrease compensation expense. The total intrinsic value of options exercised was $10.2 million , $2.5 million , and $3.1 million in 2017 , 2016 , and 2015 , respectively. The total fair value of options that vested was $1.0 million , $0.3 million , and $0.8 million in 2017 , 2016 , and 2015 , respectively. At December 30, 2017 , the aggregate intrinsic value of all outstanding options was $12.4 million with a weighted average remaining contractual term of 6.2 years. Of the outstanding options, 476 thousand are currently exercisable with an aggregate intrinsic value of $8.5 million , a weighted average exercise price of $17.57 , and a weighted average remaining contractual term of 4.5 years. The total compensation expense not yet recognized related to unvested options at December 30, 2017 was $1.9 million with an average expense recognition period of 3.5 years. Restricted Stock Awards The fair value of each restricted stock award equals the fair value of the Company’s stock on the grant date and is amortized into compensation expense on a straight-line or accrual basis over its vesting period based on its vesting schedule. The weighted average grant-date fair value of awards granted during 2017 , 2016 , and 2015 was $30.97 , $34.04 , and $32.54 , respectively. The aggregate intrinsic value of outstanding and unvested awards was $27.7 million at December 30, 2017 . Total compensation expense for restricted stock awards not yet recognized was $15.8 million with an average expense recognition period of 3.2 years. The total fair value of awards that vested was $3.5 million , $4.7 million , and $4.8 million in 2017 , 2016 , and 2015 , respectively. The Company generally issues treasury shares when options are exercised or restricted stock awards are granted. A summary of the activity and related information follows: Stock Options Restricted Stock Awards (Shares in thousands) Shares Weighted Average Exercise Price Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 1,034 $ 21.24 709 $ 31.02 Granted 165 31.04 209 30.97 Exercised (395 ) 12.10 (135 ) 26.22 Forfeited (10 ) 26.68 (2 ) 33.13 Equitable Adjustment (1) 153 — Outstanding at December 30, 2017 947 22.31 781 31.83 (1) Represents the adjustment made in conjunction with the special dividend issued on March 9, 2017 to equalize the intrinsic value of stock options pre- and post-distribution. Approximately 0.7 million shares were available for future stock incentive awards at December 30, 2017 .

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 30, 2017
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) AOCI includes certain foreign currency translation adjustments from those subsidiaries not using the U.S. dollar as their functional currency, net deferred gains and losses on certain derivative instruments accounted for as cash flow hedges, adjustments to pension and OPEB liabilities, unrealized gains and losses on marketable securities classified as available-for-sale, and other comprehensive income attributable to unconsolidated affiliates. The following table provides changes in AOCI by component, net of taxes and noncontrolling interest (amounts in parentheses indicate debits to AOCI): (In thousands) Cumulative Translation Adjustment Unrealized (Loss) Gain on Derivatives Pension/ Unrealized Gain on Equity Securities Attributable to Unconsol. Affiliates Total Balance at December 26, 2015 $ (24,773 ) $ (2,009 ) $ (28,429 ) $ 221 $ — $ (54,990 ) Other comprehensive (loss) income before reclassifications (25,192 ) 400 3,962 159 5,975 (14,696 ) Amounts reclassified from AOCI — 1,309 1,421 — — 2,730 Balance at December 31, 2016 (49,965 ) (300 ) (23,046 ) 380 5,975 (66,956 ) Other comprehensive income (loss) before reclassifications 15,579 (389 ) 1,394 (1 ) 895 17,478 Amounts reclassified from AOCI (3,777 ) 1,536 1,042 (379 ) — (1,578 ) Balance at December 30, 2017 $ (38,163 ) $ 847 $ (20,610 ) $ — $ 6,870 $ (51,056 ) Reclassification adjustments out of AOCI were as follows: Amount reclassified from AOCI (In thousands) 2017 2016 2015 Affected Line Item Unrealized losses on derivatives: Commodity contracts $ 1,309 $ 1,061 $ 4,486 Cost of goods sold Interest rate swap 851 361 372 Interest expense (624 ) (113 ) (1,310 ) Income tax benefit $ 1,536 $ 1,309 $ 3,548 Net of tax and noncontrolling interests Amortization of net loss and prior service cost on employee benefit plans $ 1,263 $ 1,942 $ 2,688 Selling, general, and administrative expense (221 ) (521 ) (719 ) Income tax benefit $ 1,042 $ 1,421 $ 1,969 Net of tax and noncontrolling interests Gain recognized upon sale of business $ (3,777 ) $ — $ — Selling, general, and administrative expense — — — Income tax expense $ (3,777 ) $ — $ — Net of tax and noncontrolling interests Sale of available-for-sale securities $ (611 ) $ — $ — Other income 232 — — Income tax expense $ (379 ) $ — $ — Net of tax and noncontrolling interests

Quarterly Financial Information

Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 30, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (Unaudited)	Quarterly Financial Information (Unaudited) (1) ( In thousands, except per share data) First Quarter Second Quarter Third Quarter Fourth Quarter 2017 Net sales $ 577,920 $ 614,266 $ 550,363 $ 523,524 Gross profit (2) 89,493 89,955 79,101 66,907 Consolidated net income (3) 30,455 27,833 22,754 5,969 (4) Net income attributable to Mueller Industries, Inc. 29,987 27,633 22,258 5,720 Basic earnings per share 0.53 0.49 0.39 0.10 Diluted earnings per share 0.52 0.48 0.39 0.10 Dividends per share 8.10 0.10 0.10 0.10 2016 Net sales $ 532,809 $ 544,071 $ 506,584 $ 472,158 Gross profit (2) 86,167 88,011 81,916 76,029 Consolidated net income (5) 28,665 28,259 26,062 (6) 16,768 (7) Net income attributable to Mueller Industries, Inc. 28,630 27,797 25,978 17,322 Basic earnings per share 0.51 0.49 0.46 0.31 Diluted earnings per share 0.50 0.49 0.45 0.30 Dividends per share 0.075 0.100 0.100 0.100 (1) The sum of quarterly amounts may not equal the annual amounts reported due to rounding. In addition, the earnings per share amounts are computed independently for each quarter, while the full year is based on the weighted average shares outstanding. (2) Gross profit is net sales less cost of goods sold, which excludes depreciation and amortization. (3) Includes income earned by Heatlink Group, acquired during Q2 2017. (4) Includes $1.1 million of pre-tax charges related to asset impairments, $4.3 million of interest expense on the Company’s Subordinated Debentures, and pre-tax environmental expense for non-operating properties of $6.2 million . (5) Includes income earned by Jungwoo-Mueller, acquired during Q2 2016. (6) Includes $3.0 million of pre-tax charges related to asset impairments. (7) Includes $3.8 million of pre-tax charges related to asset impairments.

SCHEDULE II-VALUATION AND QUALI

SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Dec. 30, 2017
Valuation and Qualifying Accounts [Abstract]
SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS	MUELLER INDUSTRIES, INC. SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS Years Ended December 30, 2017 , December 31, 2016 , and December 26, 2015 Additions (In thousands) Balance at beginning of year Charged to costs and expenses Other additions Deductions Balance at end of year 2017 Allowance for doubtful accounts $ 637 $ 422 $ (61 ) $ 18 $ 980 Environmental reserves $ 21,864 $ 7,491 $ — $ 1,351 $ 28,004 Valuation allowance for deferred tax assets $ 18,681 $ 7 $ 11,628 (1) $ — $ 30,316 2016 Allowance for doubtful accounts $ 623 $ 160 $ 2 $ 148 $ 637 Environmental reserves $ 21,667 $ 894 $ — $ 697 $ 21,864 Valuation allowance for deferred tax assets $ 17,650 $ 3 $ 1,028 $ — $ 18,681 2015 Allowance for doubtful accounts $ 666 $ (130 ) $ 201 $ 114 $ 623 Environmental reserves $ 22,661 $ 76 $ — $ 1,070 $ 21,667 Valuation allowance for deferred tax assets $ 17,119 $ (5 ) $ 536 $ — $ 17,650 (1) The valuation allowance increased by $11.6 million during 2017 to a balance of $30.3 million as of December 30, 2017. The change to the valuation allowance in 2017 was attributable to the recording of valuation allowances against tax attributes generated in 2017 primarily resulting from the Act and increased interest expense in state tax jurisdictions where the Company has no tax liability.

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 30, 2017
Accounting Policies [Abstract]
Fiscal Years	Fiscal Years The Company’s fiscal year ends on the last Saturday of December, and consisted of 52 weeks in 2017 , 53 weeks in 2016 , and 52 weeks in 2015 . These dates were December 30, 2017 , December 31, 2016 , and December 26, 2015 .
Basis of Presentation	Basis of Presentation The Consolidated Financial Statements include the accounts of Mueller Industries, Inc. and its majority-owned subsidiaries. The noncontrolling interests represent separate private ownership interests of 40 percent of Jungwoo Metal Ind. Co., LTD (Jungwoo-Mueller) and 49.5 percent of Jiangsu Mueller-Xingrong Copper Industries Limited (Mueller-Xingrong), which the Company sold during 2017 .
Revenue Recognition	Revenue Recognition Revenue is recognized when title and risk of loss pass to the customer, provided collection is determined to be probable and no significant obligations remain for the Company. Estimates for future rebates on certain product lines and product returns are recognized in the period in which the revenue is recorded. The cost of shipping product to customers is expensed as incurred as a component of cost of goods sold.
Acquisitions	Acquisitions Accounting for acquisitions requires the Company to recognize separately from goodwill the assets acquired and liabilities assumed at their acquisition date fair values. Goodwill is measured as the excess of the purchase price over the net amount allocated to the identifiable assets acquired and liabilities assumed. While management uses its best estimates and assumptions to accurately value assets acquired and liabilities assumed at the acquisition date, the estimates are inherently uncertain and subject to refinement. As a result, during the measurement period, which may be up to one year from the acquisition date, the Company may record adjustments to the assets acquired and liabilities assumed with the corresponding offset to goodwill. The operating results generated by the acquired businesses are included in the Consolidated Statements of Income from their respective dates of acquisition. Acquisition related costs are expensed as incurred.
Cash Equivalents	Cash Equivalents Temporary investments with original maturities of three months or less are considered to be cash equivalents. These investments are stated at cost. At December 30, 2017 and December 31, 2016 , temporary investments consisted of money market mutual funds, commercial paper, bank repurchase agreements, and U.S. and foreign government securities totaling $0.6 million and $40.9 million , respectively. Included in other current assets is restricted cash of $6.2 million and $9.0 million at December 30, 2017 and December 31, 2016 , respectively. These amounts represent required deposits into brokerage accounts that facilitate the Company’s hedging activities, and in 2016 included deposits that secured certain short-term notes issued under Mueller-Xingrong’s credit facility and funds received in conjunction with the New Markets Tax Credit transactions; see “ Note 10 – New Markets Tax Credit Transaction ” for additional information.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts The Company provides an allowance for receivables that may not be fully collected. In circumstances where the Company is aware of a customer’s inability to meet their financial obligations (e.g., bankruptcy filings or substantial credit rating downgrades), it records an allowance for doubtful accounts against amounts due to reduce the net recognized receivable to the amount it believes most likely will be collected. For all other customers, the Company recognizes an allowance for doubtful accounts based on its historical collection experience. If circumstances change (e.g., greater than expected defaults or an unexpected material change in a major customer’s ability to meet their financial obligations), the Company could change its estimate of the recoverability of amounts due by a material amount.
Inventories	Inventories The Company’s inventories are valued at the lower-of-cost-or-market. The material component of its U.S. copper tube and copper fittings inventories is valued on a LIFO basis and the non-material components of U.S. copper tube and copper fittings inventories are valued on a FIFO basis. The material component of its U.K. and Canadian copper tube inventories are valued on a FIFO basis. The material component of its brass rod and forgings inventories are valued on a FIFO basis. Certain inventories purchased for resale are valued on an average cost basis. Elements of cost in finished goods inventory in addition to the cost of material include depreciation, amortization, utilities, maintenance, production wages, and transportation costs. The market price of copper cathode and scrap is subject to volatility. During periods when open market prices decline below net book value, the Company may need to provide an allowance to reduce the carrying value of its inventory. In addition, certain items in inventory may be considered obsolete and, as such, the Company may establish an allowance to reduce the carrying value of those items to their net realizable value. Changes in these estimates related to the value of inventory, if any, may result in a materially adverse impact on the Company’s reported financial position or results of operations. The Company recognizes the impact of any changes in estimates, assumptions, and judgments in income in the period in which it is determined.
Property, Plant, and Equipment	Property, Plant, and Equipment Property, plant, and equipment is stated at cost less accumulated depreciation. Expenditures for major additions and improvements are capitalized, while minor replacements, maintenance, and repairs are charged to expense as incurred. Depreciation of buildings, machinery, and equipment is provided on the straight-line method over the estimated useful lives ranging from 20 to 40 years for buildings and five to 20 years for machinery and equipment. Leasehold improvements are amortized over the lesser of their useful life or the remaining lease term. The Company continually evaluates these assets to determine whether events or changes in circumstances have occurred that may warrant revision of the estimated useful life or whether the remaining balance should be evaluated for possible impairment.
Goodwill	Goodwill Goodwill is recognized for the excess of the purchase price over the fair value of tangible and identifiable intangible net assets of businesses acquired. Several factors give rise to goodwill in business acquisitions, such as the expected benefit from synergies of the combination and the existing workforce of the acquired business. Goodwill is evaluated annually for possible impairment as of the first day of the fourth quarter unless circumstances indicate the need to accelerate the timing of the evaluation. In the evaluation of goodwill impairment, management performs a qualitative assessment to determine if it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If the qualitative assessment is not conclusive, management compares the fair value of a reporting unit with its carrying amount and will recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value, not to exceed the total amount of goodwill allocated to the reporting unit. Fair value for the Company’s reporting units is determined using a combination of the income and market approaches (level 3 within the fair value hierarchy), incorporating market participant considerations and management’s assumptions on revenue growth rates, operating margins, discount rates and expected capital expenditures. The market approach measures the fair value of a business through the analysis of publicly traded companies or recent sales of similar businesses. The income approach uses a discounted cash flow model to estimate the fair value of reporting units based on expected cash flows (adjusted for capital investment required to support operations) and a terminal value. This cash flow stream is discounted to its present value to arrive at a fair value for each reporting unit. Future earnings are estimated using the Company’s most recent annual projections, applying a growth rate to future periods. Those projections are directly impacted by the condition of the markets in which the Company’s businesses participate. The discount rate selected for the reporting units is generally based on rates of return available for comparable companies at the date of valuation. Fair value determinations may include both internal and third-party valuations.
Investment in Unconsolidated Affiliate	Investment in Unconsolidated Affiliates The Company owns a 50 percent interest in Tecumseh Products Holding LLC (Joint Venture), an unconsolidated affiliate that acquired Tecumseh Products Company (Tecumseh). The Company also owns a 50 percent interest in a second unconsolidated affiliate that provides financing to Tecumseh. These investments are recorded using the equity method of accounting, as the Company can exercise significant influence but does not own a majority equity interest or otherwise control the respective entities. Under the equity method of accounting, investments are stated at initial cost and are adjusted for subsequent additional investments and the Company’s proportionate share of earnings or losses and distributions. The Company records its proportionate share of the investee’s net income or loss one quarter in arrears as income (loss) from unconsolidated affiliates, net of tax, in the Consolidated Statements of Income. The Company’s proportionate share of the investees’ other comprehensive income (loss), net of income taxes, is recorded in the Consolidated Statements of Comprehensive Income and Consolidated Statements of Changes in Equity. In general, the equity investment in the unconsolidated affiliates is equal to the current equity investment plus the investees’ undistributed earnings. The investment in unconsolidated affiliates is assessed periodically for impairment and is written down when the carrying amount is not considered fully recoverable.
Self-Insurance Accruals	Self-Insurance Accruals The Company is primarily self-insured for workers’ compensation claims and benefits paid under certain employee health care programs. Accruals are primarily based on estimated undiscounted cost of claims, which includes incurred but not reported claims, and are classified as accrued wages and other employee costs.
Pension and Other Postretirement Benefit Plans	Pension and Other Postretirement Benefit Plans The Company sponsors several qualified and nonqualified pension and other postretirement benefit plans in the U.S. and certain foreign locations. The Company recognizes the overfunded or underfunded status of the plans as an asset or liability in the Consolidated Balance Sheets with changes in the funded status recorded through comprehensive income in the year in which those changes occur. The obligations for these plans are actuarially determined and affected by assumptions, including discount rates, expected long-term return on plan assets for defined benefit pension plans, and certain employee-related factors, such as retirement age and mortality. The Company evaluates its assumptions periodically and makes adjustments as necessary. The expected return on plan assets is determined using the market value of plan assets. Differences between assumed and actual returns are amortized to the market value of assets on a straight-line basis over the average remaining service period of the plan participants using the corridor approach. The corridor approach defers all actuarial gains and losses resulting from variances between actual results and actuarial assumptions. These unrecognized gains and losses are amortized when the net gains and losses exceed 10 percent of the greater of the market value of the plan assets or the projected benefit obligation. The amount in excess of the corridor is amortized over the average remaining service period of the plan participants. For 2017 , the average remaining service period for the pension plans was nine years .
Environmental Reserves and Environmental Expenses	Environmental Reserves and Environmental Expenses The Company recognizes an environmental liability when it is probable the liability exists and the amount is reasonably estimable. The Company estimates the duration and extent of its remediation obligations based upon reports of outside consultants, internal and third party estimates and analyses of cleanup costs and ongoing monitoring costs, communications with regulatory agencies, and changes in environmental law. If the Company were to determine that its estimates of the duration or extent of its environmental obligations were no longer accurate, it would adjust environmental liabilities accordingly in the period that such determination is made. Estimated future expenditures for environmental remediation are not discounted to their present value. Environmental expenses that relate to ongoing operations are included as a component of cost of goods sold. Environmental expenses related to non-operating properties are presented below operating income in the Consolidated Statements of Income.
Earnings Per Share	Earnings Per Share Basic earnings per share is computed based on the weighted average number of common shares outstanding. Diluted earnings per share reflects the increase in weighted average common shares outstanding that would result from the assumed exercise of outstanding stock options and vesting of restricted stock awards calculated using the treasury stock method.
Income Taxes	Income Taxes Deferred income tax assets and liabilities are recognized when differences arise between the treatment of certain items for financial statement and tax purposes. Realization of certain components of deferred tax assets is dependent upon the occurrence of future events. The Company records valuation allowances to reduce its deferred tax assets to the amount it believes is more likely than not to be realized. These valuation allowances can be impacted by changes in tax laws, changes to statutory tax rates, and future taxable income levels and are based on the Company’s judgment, estimates, and assumptions regarding those future events. In the event the Company was to determine that it would not be able to realize all or a portion of the net deferred tax assets in the future, it would increase the valuation allowance through a charge to income tax expense in the period that such determination is made. Conversely, if it was to determine that it would be able to realize its deferred tax assets in the future, in excess of the net carrying amounts, the Company would decrease the recorded valuation allowance through a decrease to income tax expense in the period that such determination is made. The Company provides for uncertain tax positions and the related interest and penalties, if any, based upon management’s assessment of whether a tax benefit is more likely than not to be sustained upon examination by tax authorities. Tax benefits for uncertain tax positions that are recognized in the financial statements are measured as the largest amount of benefit, determined on a cumulative probability basis, that is more likely than not to be realized upon ultimate settlement. To the extent the Company prevails in matters for which a liability for an uncertain tax position is established or is required to pay amounts in excess of the liability, the Company’s effective tax rate in a given financial statement period may be affected. These estimates are highly subjective and could be affected by changes in business conditions and other factors. Changes in any of these factors could have a material impact on future income tax expense.
Taxes Collected from Customers and Remitted to Governmental Authorities	Taxes Collected from Customers and Remitted to Governmental Authorities Taxes assessed by a governmental authority that are directly imposed on a revenue producing transaction between the Company and its customers, primarily value added taxes in foreign jurisdictions, are accounted for on a net (excluded from revenues and costs) basis.
Stock-Based Compensation	Stock-Based Compensation The Company has in effect stock incentive plans under which stock-based awards have been granted to certain employees and members of its Board of Directors. Stock-based compensation expense is recognized in the Consolidated Statements of Income as a component of selling, general, and administrative expense based on the grant date fair value of the awards.
Concentrations of Credit and Market Risk	Concentrations of Credit and Market Risk Concentrations of credit risk with respect to accounts receivable are limited due to the large number of customers comprising the Company’s customer base, and their dispersion across different geographic areas and different industries, including HVAC, plumbing, refrigeration, hardware, automotive, OEMs, and others. The Company minimizes its exposure to base metal price fluctuations through various strategies. Generally, it prices an equivalent amount of copper raw material, under flexible pricing arrangements it maintains with its suppliers, at the time it determines the selling price of finished products to its customers.
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities The Company’s earnings and cash flows are subject to fluctuations due to changes in commodity prices, foreign currency exchange rates, and interest rates. The Company uses derivative instruments such as commodity futures contracts, foreign currency forward contracts, and interest rate swaps to manage these exposures. All derivatives are recognized in the Consolidated Balance Sheets at their fair value. On the date the derivative contract is entered into, it is either a) designated as a hedge of (i) a forecasted transaction or the variability of cash flow to be paid (cash flow hedge) or (ii) the fair value of a recognized asset or liability (fair value hedge), or b) not designated in a hedge accounting relationship, even though the derivative contract was executed to mitigate an economic exposure (economic hedge), as the Company does not enter into derivative contracts for trading purposes. Changes in the fair value of a derivative that is qualified, designated, and highly effective as a cash flow hedge are recorded in stockholders’ equity within accumulated other comprehensive income (AOCI), to the extent effective, until they are reclassified to earnings in the same period or periods during which the hedged transaction affects earnings. Changes in the fair value of a derivative that is qualified, designated, and highly effective as a fair value hedge, along with the gain or loss on the hedged recognized asset or liability that is attributable to the hedged risk, are recorded in current earnings. Changes in the fair value of undesignated derivative instruments executed as economic hedges and the ineffective portion of designated derivatives are reported in current earnings. The Company documents all relationships between derivative instruments and hedged items, as well as the risk-management objective and strategy for undertaking various hedge transactions. This process includes linking all derivative instruments that are designated as fair value hedges to specific assets and liabilities in the Consolidated Balance Sheets and linking cash flow hedges to specific forecasted transactions or variability of cash flow. The Company also assesses, both at the hedge’s inception and on an ongoing basis, whether the designated derivative instruments that are used in hedging transactions are highly effective in offsetting changes in cash flow or fair values of hedged items. When a derivative instrument is determined not to be highly effective as a hedge or the underlying hedged transaction is no longer probable of occurring, hedge accounting is discontinued prospectively in accordance with the derecognition criteria for hedge accounting. The Company primarily executes derivative contracts with major financial institutions. These counterparties expose the Company to credit risk in the event of non-performance. The amount of such exposure is limited to the fair value of the contract plus the unpaid portion of amounts due to the Company pursuant to terms of the derivative instruments, if any. If a downgrade in the credit rating of these counterparties occurs, management believes that this exposure is mitigated by provisions in the derivative arrangements which allow for the legal right of offset of any amounts due to the Company from the counterparties with any amounts payable to the counterparties by the Company. As a result, management considers the risk of loss from counterparty default to be minimal.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts for cash and cash equivalents, accounts receivable, and accounts payable approximate fair value due to the short-term maturity of these instruments. The fair value of long-term debt at December 30, 2017 approximates the carrying value on that date. The estimated fair values were determined based on quoted market prices and the current rates offered for debt with similar terms and maturities. The fair value of long-term debt is classified as level 2 within the fair value hierarchy. This classification is defined as a fair value determined using market-based inputs other than quoted prices that are observable for the liability, either directly or indirectly.
Foreign Currency Translation	Foreign Currency Translation For foreign subsidiaries in which the functional currency is not the U.S. dollar, balance sheet accounts are translated at exchange rates in effect at the end of the year and income statement accounts are translated at average exchange rates for the year. Translation gains and losses are included in equity as a component of AOCI. Transaction gains and losses that arise from exchange rate fluctuations on transactions denominated in a currency other than the functional currency are recognized in selling, general, and administrative expense in the Consolidated Statements of Income.
Use of and Changes in Estimates	Use of and Changes in Estimates The preparation of financial statements in conformity with generally accepted accounting principles in the United States (U.S. GAAP) requires management to make estimates, assumptions, and judgments that affect the amounts reported in the financial statements and accompanying notes. Management makes its best estimate of the ultimate outcome for these items based on historical trends and other information available when the financial statements are prepared. Changes in estimates are recognized in accordance with the accounting rules for the estimate, which is typically in the period when new information becomes available to management. Areas where the nature of the estimate makes it reasonably possible that actual results could materially differ from amounts estimated include but are not limited to: pension and other postretirement benefit plan obligations, tax liabilities, loss contingencies, litigation claims, environmental reserves, and impairment assessments on long-lived assets (including goodwill).
Change in Segment Reporting	Change in Segment Reporting At the beginning of fiscal year 2016 , the Company made changes to its management reporting structure as a result of a change in the way the Chief Executive Officer, who serves as the Chief Operating Decision Maker, manages and evaluates the business, makes key operating decisions, and allocates resources. Previously, the Company had two reportable segments: Plumbing & Refrigeration and OEM. During 2016 , the Company realigned its operating segments into three reportable segments: Piping Systems, Industrial Metals, and Climate. Management has recast certain prior year amounts to conform to the current year presentation.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In February 2018, the FASB issued ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . The ASU permits entities to reclassify tax effects stranded in AOCI as a result of tax reform to retained earnings. The guidance is effective for the Company in interim and annual periods beginning in 2019. Early adoption is permitted and can be applied retrospectively or in the period of adoption. The Company does not expect the adoption of the standard to have a material impact on its Consolidated Financial Statements. In March 2017, the FASB issued ASU No. 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . The ASU requires employers that sponsor defined benefit pension and/or other postretirement benefit plans to present the service cost component of net periodic benefit cost in the same income statement line item(s) as other employee compensation costs arising from services rendered during the period and other components of net periodic benefits cost separately from the line item(s) that includes the service cost and outside of any subtotal of operating income. The guidance is effective for the Company in interim and annual periods beginning in 2018. Early adoption is permitted as of the beginning of an annual period for which financial statements have not been issued or made available for issuance. The Company does not expect the adoption of the standard to have a material impact on its Consolidated Financial Statements. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business . The ASU provides guidance to assist entities in evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The updated guidance requires a prospective adoption. Early adoption is permitted. This update will be effective for the Company beginning in 2018. The Company does not expect the provisions of the ASU to have a material impact on its Consolidated Financial Statements. In December 2016, the FASB issued ASU No. 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers . The ASU provides correction or improvement to the guidance previously issued in ASU 2014-09, Revenue from Contracts with Customers (Topic 606) . Under the ASU, an entity will recognize revenue to depict the transfer of promised goods or services to customers at an amount that reflects the consideration that it expects to receive in exchange for the goods or services. It also requires more detailed disclosures to enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. This guidance is effective for the Company at the beginning of 2018. The standard permits the use of either the full retrospective or cumulative transition effect (modified retrospective) method. The ASU requires revenue to be recognized over time (i.e., throughout the production process) rather than at a point in time (generally upon shipment to the customer) if performance does not create an asset with an alternative use to the entity and the entity has an enforceable right to payment for performance completed to date. The Company has evaluated specific contract terms, primarily within the Industrial Metals and Climate segments, related to the production of customized products and payment rights and determined that there will be no significant changes to the timing of revenue recognition under the ASU. As part of the overall evaluation of the standard, the Company has assessed changes to its accounting policies, practices, and internal controls over financial reporting to support the standard. The Company does not expect the adoption of the standard to have a material impact on its Consolidated Financial Statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash . The ASU requires entities to show the changes in the total of cash, cash equivalents, restricted cash, and restricted cash equivalents in the statement of cash flows. As a result, entities will no longer present transfers between cash and cash equivalents and restricted cash and restricted cash equivalents in the statement of cash flows. The guidance will be applied retrospectively and is effective for the Company beginning in 2018. Early adoption is permitted. The Company does not expect the adoption of the standard to have a material impact on its Consolidated Financial Statements. In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory . The ASU requires companies to account for the income tax effects of intercompany transfers of assets other than inventory when the transfer occurs. Companies will still be required to defer the income tax effects of intercompany inventory transactions in an exception to the income tax accounting guidance. The guidance is effective for the Company beginning in 2018. Early adoption is permitted as of the beginning of an annual period. The Company is still evaluating the effects that the provisions of the ASU will have on its Consolidated Financial Statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . The ASU requires an entity to recognize a right-of-use asset and lease liability for all leases with terms of more than 12 months. Recognition, measurement and presentation of expenses will depend on classification as a financing or operating lease. The amendments also require certain quantitative and qualitative disclosures about leasing arrangements. The ASU will be effective for interim and fiscal periods beginning in 2018. Early adoption is permitted. Currently the guidance requires a modified retrospective adoption, but in January 2018 the FASB proposed ASU No. 2018-01, Leases (Topic 842) , which if approved will allow entities to elect a simplified transition approach whereby they would apply the provisions of the new guidance at the effective date without adjusting the comparative periods presented. The Company is still evaluating the effects that the provision of ASU 2016-02 will have on its Consolidated Financial Statements.

Acquisitions and Dispositions (

Acquisitions and Dispositions (Tables)	12 Months Ended
	Dec. 30, 2017
Acquisitions and Dispositions [Abstract]
Schedule of final valuation of the long-lived assets	The following table summarizes the allocation of the purchase price to acquire these businesses, which was financed by available cash balances, as well as the assets acquired and liabilities assumed at the respective acquisition dates. The purchase price allocation for Heatlink Group is provisional as of December 30, 2017 and subject to change upon completion of the final valuation of the long-lived assets during the measurement period. During 2017 , the valuation of the Jungwoo-Mueller acquisition was finalized and changes to the purchase price allocation from the amounts presented in the Company’s 2016 Consolidated Financial Statements were immaterial. (in thousands) Heatlink Group Jungwoo-Mueller Great Lakes Sherwood Turbotec Total consideration $ 16,317 $ 20,533 $ 70,011 $ 21,795 $ 14,138 Allocated to: Accounts receivable 2,809 5,551 26,079 6,490 1,936 Inventories 4,648 17,616 15,233 11,892 3,247 Other current assets 508 1,437 22 260 72 Property, plant, and equipment 2,024 24,191 22,771 10,327 9,080 Goodwill 4,071 223 23,208 (1) — 2,088 Intangible assets 6,413 756 27,468 (38 ) 880 Other assets — 277 1,413 — 59 Total assets acquired 20,473 50,051 116,194 28,931 17,362 Accounts payable 3,633 7,252 36,026 6,022 1,603 Accrued wages & other employee costs — — — 471 356 Other current liabilities 523 577 381 487 51 Long-term debt — 8,659 — — — Pension and other postretirement liabilities — 799 5,655 — — Other noncurrent liabilities — 582 4,121 156 1,214 Total liabilities assumed 4,156 17,869 46,183 7,136 3,224 Noncontrolling interest — 11,649 — — — Net assets acquired $ 16,317 $ 20,533 $ 70,011 $ 21,795 $ 14,138 (1) Tax-deductible goodwill
Intangible assets identified in the allocation of the purchase price	The following details the total intangible assets identified in the allocation of the purchase price at the respective acquisition dates: (in thousands) Estimated Useful Life Heatlink Group Jungwoo-Mueller Great Lakes Turbotec Intangible asset type: Customer relationships 20 years $ 4,265 $ — $ 20,273 $ 350 Non-compete agreements 3-5 years 74 — 2,269 90 Patents and technology 10-15 years 1,466 756 3,104 220 Trade names, licenses, and other 5-10 years 608 — 1,822 220 Total intangible assets $ 6,413 $ 756 $ 27,468 $ 880

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 30, 2017
Segment Reporting [Abstract]
Net sales by major product line	Net Sales by Major Product Line: (In thousands) 2017 2016 2015 Tube and fittings $ 1,260,105 $ 1,072,242 $ 1,053,761 Brass rod and forgings 450,063 371,237 436,456 OEM components, tube & assemblies 272,567 327,327 342,651 Valves and plumbing specialties 200,409 209,217 198,012 Other 82,929 75,599 69,122 $ 2,266,073 $ 2,055,622 $ 2,100,002
Geographic information	Geographic Information: (In thousands) 2017 2016 2015 Net sales: United States $ 1,556,825 $ 1,400,893 $ 1,519,456 United Kingdom 231,039 197,039 240,823 Canada 280,140 237,162 97,967 Asia 121,295 149,875 162,664 Mexico 76,774 70,653 79,092 $ 2,266,073 $ 2,055,622 $ 2,100,002 (In thousands) 2017 2016 2015 Long-lived assets: United States $ 238,752 $ 223,099 $ 223,398 United Kingdom 17,661 15,978 19,982 Canada 21,327 18,928 20,460 Asia 25,973 36,722 15,863 Mexico 608 504 521 $ 304,321 $ 295,231 $ 280,224
Summary of segment information	Summarized segment information is as follows: For the Year Ended December 30, 2017 (In thousands) Piping Systems Industrial Metals Climate Corporate and Eliminations Total Net sales $ 1,564,950 $ 602,131 $ 131,448 $ (32,456 ) $ 2,266,073 Cost of goods sold 1,369,161 506,973 98,851 (34,368 ) 1,940,617 Depreciation and amortization 21,777 7,516 2,513 2,138 33,944 Selling, general, and administrative expense 74,479 11,890 9,759 43,452 139,580 Gain on sale of businesses (1,491 ) — — — (1,491 ) Impairment charges 1,466 — — — 1,466 Operating income 99,558 75,752 20,325 (43,678 ) 151,957 Interest expense (19,502 ) Environmental expense (7,284 ) Other income, net 1,801 Income before income taxes $ 126,972 Segment information (continued): For the Year Ended December 31, 2016 (In thousands) Piping Systems Industrial Metals Climate Corporate and Eliminations Total Net sales $ 1,429,589 $ 521,060 $ 119,758 $ (14,785 ) $ 2,055,622 Cost of goods sold 1,228,949 420,905 89,927 (16,282 ) 1,723,499 Depreciation and amortization 22,421 8,162 2,437 2,113 35,133 Selling, general, and administrative expense 68,218 13,162 9,661 46,458 137,499 Impairment charges 6,115 663 — — 6,778 Operating income 103,886 78,168 17,733 (47,074 ) 152,713 Interest expense (7,387 ) Environmental expense (1,279 ) Other income, net 1,983 Income before income taxes $ 146,030 For the Year Ended December 26, 2015 (In thousands) Piping Systems Industrial Metals Climate Corporate and Eliminations Total Net sales $ 1,436,689 $ 567,467 $ 110,727 $ (14,881 ) $ 2,100,002 Cost of goods sold 1,245,929 491,567 86,894 (14,688 ) 1,809,702 Depreciation and amortization 22,559 7,503 2,257 2,289 34,608 Selling, general, and administrative expense 66,903 10,955 9,117 43,383 130,358 Gain on sale of businesses (15,376 ) — — — (15,376 ) Severance 3,442 — — — 3,442 Operating income 113,232 57,442 12,459 (45,865 ) 137,268 Interest expense (7,667 ) Environmental expense (46 ) Other income, net 2,234 Income before income taxes $ 131,789
Segment information by assets	(In thousands) 2017 2016 2015 Expenditures for long-lived assets (including those resulting from business acquisitions): Piping Systems $ 18,124 $ 56,286 $ 41,900 Industrial Metals 5,322 3,302 16,603 Climate 2,191 2,045 12,373 General Corporate 22,518 55 136 $ 48,155 $ 61,688 $ 71,012 During the fourth quarter of 2017 , the Company took early delivery of a Corporate aircraft to replace its existing aircraft. Subsequent to year-end, the existing aircraft was taken out of service and classified as held-for-sale, and the Company expects to recognize an impairment charge of approximately $3.3 million in the first quarter of 2018. The Company expects to sell the aircraft in 2018. Segment assets: Piping Systems $ 801,468 $ 826,663 $ 811,343 Industrial Metals 212,638 160,478 153,102 Climate 73,458 66,968 61,672 General Corporate 232,609 393,367 312,684 $ 1,320,173 $ 1,447,476 $ 1,338,801

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 30, 2017
Inventory Disclosure [Abstract]
Inventories	(In thousands) 2017 2016 Raw materials and supplies $ 108,397 $ 57,387 Work-in-process 46,158 42,227 Finished goods 180,143 149,288 Valuation reserves (6,797 ) (6,889 ) Inventories $ 327,901 $ 242,013

Consolidated Financial Statem32

Consolidated Financial Statement Details (Tables)	12 Months Ended
	Dec. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Other (expense) income, net	Other Income, Net (In thousands) 2017 2016 2015 Interest income $ 684 $ 1,185 $ 1,029 Other 1,117 798 1,205 Other income, net $ 1,801 $ 1,983 $ 2,234

Derivative Instruments and He33

Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Dec. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative instruments designated as cash flow hedges reflected in the financial statements	The following table summarizes the location and fair value of the derivative instruments and disaggregates the net derivative assets and liabilities into gross components on a contract-by-contract basis: Asset Derivatives Liability Derivatives Fair Value Fair Value (In thousands) Balance Sheet Location 2017 2016 Balance Sheet Location 2017 2016 Commodity contracts - gains Other current assets $ 1,014 $ 1,013 Other current liabilities $ 55 $ 564 Commodity contracts - losses Other current assets (5 ) (148 ) Other current liabilities (3,210 ) (920 ) Interest rate swap Other current assets — — Other current liabilities — (787 ) Total derivatives (1) $ 1,009 $ 865 $ (3,155 ) $ (1,143 ) (1) Does not include the impact of cash collateral provided to counterparties .
Schedule of fair value hedges	The following tables summarize the effects of derivative instruments on the Consolidated Statements of Income: (In thousands) Location 2017 2016 Fair value hedges: Loss on commodity contracts (qualifying) Cost of goods sold $ (724 ) $ (420 ) Gain on hedged item - inventory Cost of goods sold 625 382 Undesignated derivatives: (Loss) gain on commodity contracts (nonqualifying) Cost of goods sold $ (6,078 ) $ 4,068
Summary of activities related to derivative instruments classified as cash flow hedges	The following tables summarize amounts recognized in and reclassified from AOCI during the period: Year Ended December 30, 2017 (In thousands) (Loss) Gain Recognized in AOCI (Effective Portion), Net of Tax Classification Gains (Losses) Loss Reclassified from AOCI (Effective Portion), Net of Tax Cash flow hedges: Commodity contracts $ (574 ) Cost of goods sold $ 990 Interest rate swap — Interest expense 546 Other 185 Other — Total $ (389 ) Total $ 1,536 Derivative instruments and hedging activities (continued): Year Ended December 31, 2016 (In thousands) Gain (Loss) Recognized in AOCI (Effective Portion), Net of Tax Classification Gains (Losses) Loss Reclassified from AOCI (Effective Portion), Net of Tax Cash flow hedges: Commodity contracts $ 308 Cost of goods sold $ 1,078 Interest rate swap 305 Interest expense 231 Other (213 ) Other — Total $ 400 Total $ 1,309

Property, Plant, and Equipmen34

Property, Plant, and Equipment, Net (Tables)	12 Months Ended
	Dec. 30, 2017
Property, Plant and Equipment [Abstract]
Property, plant, and equipment, net	(In thousands) 2017 2016 Land and land improvements $ 18,740 $ 19,928 Buildings 144,527 144,914 Machinery and equipment 649,667 607,344 Construction in progress 9,274 30,344 822,208 802,530 Less accumulated depreciation (517,887 ) (507,299 ) Property, plant, and equipment, net $ 304,321 $ 295,231

Goodwill and Other Intangible35

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the carrying amount of goodwill	The changes in the carrying amount of goodwill by segment were as follows: (In thousands) Piping Systems Industrial Metals Climate Total Goodwill $ 156,387 $ 8,854 $ 4,416 $ 169,657 Accumulated impairment charges (40,552 ) (8,853 ) — (49,405 ) Balance at December 26, 2015: 115,835 1 4,416 120,252 Additions (1) 4,601 — — 4,601 Currency translation (860 ) — — (860 ) Balance at December 31, 2016: 119,576 1 4,416 123,993 Additions (2) 3,852 — — 3,852 Currency translation 2,448 — — 2,448 Balance at December 30, 2017: Goodwill 166,428 8,854 4,416 179,698 Accumulated impairment charges (40,552 ) (8,853 ) — (49,405 ) Goodwill, net $ 125,876 $ 1 $ 4,416 $ 130,293 (1) Includes finalization of the purchase price allocation adjustment for Great Lakes of $4.1 million . (2) Includes finalization of the purchase price allocation adjustment for Jungwoo-Mueller of $0.2 million .
Carrying amount of intangible assets	The carrying amount of intangible assets at December 30, 2017 was as follows: (In thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Customer relationships $ 36,518 $ (4,644 ) $ 31,874 Non-compete agreements 2,834 (1,497 ) 1,337 Patents and technology 7,673 (1,868 ) 5,805 Trade names and licenses 4,977 (1,575 ) 3,402 Other 213 (623 ) (410 ) Other intangible assets $ 52,215 $ (10,207 ) $ 42,008 The carrying amount of intangible assets at December 31, 2016 was as follows: (In thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Customer relationships $ 29,833 $ (2,845 ) $ 26,988 Non-compete agreements 5,926 (4,063 ) 1,863 Patents and technology 5,922 (1,179 ) 4,743 Trade names and licenses 4,087 (1,032 ) 3,055 Other 213 (694 ) (481 ) Other intangible assets $ 45,981 $ (9,813 ) $ 36,168
Amortization expense for intangible assets	Future amortization expense is estimated as follows: (In thousands) Amount 2018 $ 3,338 2019 3,253 2020 3,017 2021 2,747 2022 2,851 Thereafter 26,802 Expected amortization expense $ 42,008

Investment in Unconsolidated 36

Investment in Unconsolidated Affiliates (Tables)	12 Months Ended
	Dec. 30, 2017
Equity Method Investments and Joint Ventures [Abstract]
Summarized financial information derived from the Company's equity method investee's consolidated financial statements	The following tables present summarized financial information derived from the Company’s equity method investees’ combined consolidated financial statements, which are prepared in accordance with U.S. GAAP. (In thousands) 2017 2016 Current assets $ 246,127 $ 244,323 Noncurrent assets 139,200 130,400 Current liabilities 174,710 148,806 Noncurrent liabilities 58,334 71,681 Net sales $ 556,600 $ 579,400 Gross profit 75,600 79,600 Net (loss) income (4,153 ) 3,720

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 30, 2017
Debt Disclosure [Abstract]
Schedule of Debt	(In thousands) 2017 2016 Subordinated Debentures with interest at 6.00%, due 2027 $ 284,536 $ — Revolving Credit Facility with interest at 3.06%, due 2021 160,000 200,000 Jungwoo-Mueller credit facility with interest at 2.72%, due 2018 5,119 4,724 Jungwoo-Mueller credit facility with interest at 3.19%, due 2017 8,648 7,990 2001 Series IRB's with interest at 2.22%, due 2021 3,250 4,250 Mueller-Xingrong credit facility — 3,048 Other 4,694 8,309 466,247 228,321 Less debt issuance costs (1,175 ) (957 ) Less current portion of debt (16,480 ) (13,655 ) Long-term debt $ 448,592 $ 213,709
Debt instrument redemption	If redeemed during the 12-month period beginning March 9: Year Redemption Price 2017 106% 2018 105 2019 104 2020 103 2021 102 2022 and thereafter 100
Aggregate annual maturities of debt	Aggregate annual maturities of the Company’s debt are as follows: (In thousands) Amount 2018 $ 16,480 2019 1,222 2020 1,222 2021 160,472 2022 222 Thereafter 286,629 Long-term debt $ 466,247
Net interest expense	Net interest expense consisted of the following: (In thousands) 2017 2016 2015 Interest expense $ 19,716 $ 7,749 $ 8,335 Capitalized interest (214 ) (362 ) (668 ) $ 19,502 $ 7,387 $ 7,667

Benefit Plans (Tables)

Benefit Plans (Tables)	12 Months Ended
	Dec. 30, 2017
Compensation and Retirement Disclosure [Abstract]
Reconciliation of the changes in the plans' benefit obligations and the fair value of the plans assets	The following tables provide a reconciliation of the changes in the plans’ benefit obligations and the fair value of the plans’ assets for 2017 and 2016 , and a statement of the plans’ aggregate funded status: Pension Benefits Other Benefits (In thousands) 2017 2016 2017 2016 Change in benefit obligation: Obligation at beginning of year $ 178,736 $ 192,761 $ 15,274 $ 15,843 Service cost 128 532 235 232 Interest cost 6,344 7,553 599 594 Actuarial loss (gain) 4,688 9,399 923 (249 ) Plan amendments — — — 43 Benefit payments (10,171 ) (17,572 ) (883 ) (1,023 ) Settlement charge — — (209 ) — Foreign currency translation adjustment 7,041 (13,937 ) 468 (166 ) Obligation at end of year 186,766 178,736 16,407 15,274 Change in fair value of plan assets: Fair value of plan assets at beginning of year 169,140 176,077 — — Actual return on plan assets 19,175 19,319 — — Employer contributions 2,271 2,377 883 1,023 Benefit payments (10,171 ) (17,572 ) (883 ) (1,023 ) Foreign currency translation adjustment 5,921 (11,061 ) — — Fair value of plan assets at end of year 186,336 169,140 — — Underfunded status at end of year $ (430 ) $ (9,596 ) $ (16,407 ) $ (15,274 )
Amounts recognized in accumulated OCI (before the effect of income taxes)	The following represents amounts recognized in AOCI (before the effect of income taxes): Pension Benefits Other Benefits (In thousands) 2017 2016 2017 2016 Unrecognized net actuarial loss $ 34,627 $ 39,986 $ 1,540 $ 614 Unrecognized prior service credit — — (7,289 ) (8,180 )
Funded status of the plans recognized	As of December 30, 2017 and December 31, 2016 , the total funded status of the plans recognized in the Consolidated Balance Sheets was as follows: Pension Benefits Other Benefits (In thousands) 2017 2016 2017 2016 Long-term asset $ 9,894 $ 4,442 $ — $ — Current liability — — (1,070 ) (1,128 ) Long-term liability (10,324 ) (14,038 ) (15,337 ) (14,146 ) Total underfunded status $ (430 ) $ (9,596 ) $ (16,407 ) $ (15,274 )
Components of net periodic benefit costs	The components of net periodic benefit cost are as follows: (In thousands) 2017 2016 2015 Pension benefits: Service cost $ 128 $ 532 $ 803 Interest cost 6,344 7,553 8,032 Expected return on plan assets (9,374 ) (9,615 ) (10,289 ) Amortization of net loss 2,206 2,898 2,710 Settlement charge — 1,214 — Net periodic benefit (income) cost $ (696 ) $ 2,582 $ 1,256 Other benefits: Service cost $ 235 $ 232 $ 363 Interest cost 599 594 1,005 Amortization of prior service (credit) cost (901 ) (896 ) 6 Amortization of net gain (42 ) (60 ) (28 ) Settlement charge 17 — — Net periodic benefit (income) cost $ (92 ) $ (130 ) $ 1,346
Weighted average assumptions used in the measurement of the Company's benefit obligation and net periodic benefit cost are as follows	The weighted average assumptions used in the measurement of the Company’s benefit obligations are as follows: Pension Benefits Other Benefits 2017 2016 2017 2016 Discount rate 3.22 % 3.61 % 3.89 % 4.21 % Expected long-term return on plan assets 5.27 % 5.56 % N/A N/A Rate of compensation increases N/A N/A 5.00 % 5.00 % Rate of inflation 3.30 % 3.30 % N/A N/A The weighted average assumptions used in the measurement of the Company’s net periodic benefit cost are as follows: Pension Benefits Other Benefits 2017 2016 2015 2017 2016 2015 Discount rate 3.61 % 4.02 % 4.03 % 4.21 % 4.25 % 4.33 % Expected long-term return on plan assets 5.56 % 5.59 % 5.58 % N/A N/A N/A Rate of compensation increases N/A N/A N/A 5.00 % 5.00 % 5.00 % Rate of inflation 3.30 % 3.20 % 3.10 % N/A N/A N/A
Weighted average asset allocation of the Company’s pension fund assets are as follows	The weighted average asset allocation of the Company’s pension fund assets are as follows: Pension Plan Assets Asset category 2017 2016 Equity securities (includes equity mutual funds) 46 % 47 % Fixed income securities (includes fixed income mutual funds) 48 48 Cash and equivalents (includes money market funds) 3 3 Alternative investments 3 2 Total 100 % 100 %
Plan assets at fair value within the fair value hierarchy, by level	The following table sets forth by level, within the fair value hierarchy, the assets of the plans at fair value: Fair Value Measurements at December 30, 2017 (In thousands) Level 1 Level 2 Level 3 Total Cash and money market funds $ 5,364 $ — $ — $ 5,364 Common stock (1) 11,113 — — 11,113 Mutual funds (2) 8,412 156,442 — 164,854 Limited partnerships — — 5,005 5,005 Total $ 24,889 $ 156,442 $ 5,005 $ 186,336 Fair Value Measurements at December 31, 2016 (In thousands) Level 1 Level 2 Level 3 Total Cash and money market funds $ 4,245 $ — $ — $ 4,245 Common stock (3) 18,601 — — 18,601 Mutual funds (4) 5,572 136,027 — 141,599 Limited partnerships — — 4,695 4,695 Total $ 28,418 $ 136,027 $ 4,695 $ 169,140 (1) Approximately 91 percent of common stock represents investments in U.S. companies primarily in the health care, utilities, financials, consumer staples, industrials, and information technology sectors. All investments in common stock are listed on U.S. stock exchanges. (2) Approximately 66 percent of mutual funds are actively managed funds and approximately 34 percent of mutual funds are index funds. Additionally, five percent of the mutual funds’ assets are invested in U.S. equities, 41 percent in non-U.S. equities, 52 percent in U.S. fixed income securities, and two percent in non-U.S. fixed income securities. (3) Approximately 90 percent of common stock represents investments in U.S. companies primarily in the health care, utilities, financials, consumer staples, industrials, and information technology sectors. All investments in common stock are listed on U.S. stock exchanges. (4) Approximately 68 percent of mutual funds are actively managed funds and approximately 32 percent of mutual funds are index funds. Additionally, five percent of the mutual funds’ assets are invested in U.S. equities, 38 percent in non-U.S. equities, 54 percent in U.S. fixed income securities, and three percent in non-U.S. fixed income securities.
Plan assets measured at fair value using significant unobservable inputs	The table below reflects the changes in the assets of the plan measured at fair value on a recurring basis using significant unobservable inputs (level 3 of fair value hierarchy) during the year ended December 30, 2017 : (In thousands) Limited Partnerships Balance, December 31, 2016 $ 4,695 Redemptions (283 ) Subscriptions 273 Net appreciation in fair value 320 Balance, December 30, 2017 $ 5,005
Future benefit plans payments	The Company expects future benefits to be paid from the plans as follows: (In thousands) Pension Benefits Other Benefits 2018 $ 10,423 $ 1,177 2019 10,398 1,056 2020 10,329 1,277 2021 10,246 1,129 2022 10,182 1,157 2023-2027 49,965 6,154 Total $ 101,543 $ 11,950

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 30, 2017
Income Tax Disclosure [Abstract]
Components of income before income taxes	The components of income before income taxes were taxed under the following jurisdictions: (In thousands) 2017 2016 2015 Domestic $ 76,876 $ 103,576 $ 121,614 Foreign 50,096 42,454 10,175 Income before income taxes $ 126,972 $ 146,030 $ 131,789
Components of income tax expense	Income tax expense consists of the following: (In thousands) 2017 2016 2015 Current tax expense: Federal $ 28,584 $ 32,262 $ 50,272 Foreign 10,219 5,667 4,042 State and local 2,241 3,210 4,886 Current tax expense 41,044 41,139 59,200 Deferred tax (benefit) expense: Federal (1,764 ) 2,004 (13,739 ) Foreign 1,118 5,099 (1,180 ) State and local (2,514 ) (105 ) (899 ) Deferred tax (benefit) expense (3,160 ) 6,998 (15,818 ) Income tax expense $ 37,884 $ 48,137 $ 43,382
Income tax reconciliation	The difference between the reported income tax expense and a tax determined by applying the applicable U.S. federal statutory income tax rate to income before income taxes is reconciled as follows: (In thousands) 2017 2016 2015 Expected income tax expense $ 44,440 $ 51,110 $ 46,126 State and local income tax, net of federal benefit 1,135 1,982 2,673 Effect of foreign statutory rate different from U.S. and other foreign adjustments (6,026 ) (4,092 ) (654 ) U.S. production activities deduction (1,575 ) (3,063 ) (3,500 ) Goodwill disposition — — 646 Investment in unconsolidated affiliates 216 1,030 — Permanent adjustment to deferred tax liabilities — — (4,218 ) Benefit of stock-based compensation deductions (2,160 ) (656 ) — Effect of tax on accumulated foreign earnings 12,893 — — Effect of tax rate change on net deferred tax liability balance (12,067 ) — — Other, net 1,028 1,826 2,309 Income tax expense $ 37,884 $ 48,137 $ 43,382
Components of deferred tax assets and liabilities	The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities are presented below: (In thousands) 2017 2016 Deferred tax assets: Inventories $ 10,598 $ 15,483 Other postretirement benefits and accrued items 9,239 13,180 Other reserves 9,029 9,821 Federal and foreign tax attributes 11,936 5,813 State tax attributes, net of federal benefit 29,720 22,572 Stock-based compensation 2,102 2,416 Basis difference in unconsolidated affiliates — 211 Total deferred tax assets 72,624 69,496 Less valuation allowance (30,316 ) (18,681 ) Deferred tax assets, net of valuation allowance 42,308 50,815 Deferred tax liabilities: Property, plant, and equipment 43,972 52,319 Pension 3,841 4,633 Basis difference in unconsolidated affiliates 203 — Total deferred tax liabilities 48,016 56,952 Net deferred tax liabilities $ (5,708 ) $ (6,137 )

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted average assumptions used in calculating fair value of stock options	The weighted average of key assumptions used in determining the fair value of options granted and a discussion of the methodology used to develop each assumption are as follows: 2017 2016 2015 Expected term 7.7 years 6.7 years 5.5 years Expected price volatility 28.9 % 25.6 % 26.2 % Risk-free interest rate 2.1 % 1.6 % 1.7 % Dividend yield 1.3 % 1.0 % 0.9 %
Summary of the stock option activity	A summary of the activity and related information follows: Stock Options Restricted Stock Awards (Shares in thousands) Shares Weighted Average Exercise Price Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 1,034 $ 21.24 709 $ 31.02 Granted 165 31.04 209 30.97 Exercised (395 ) 12.10 (135 ) 26.22 Forfeited (10 ) 26.68 (2 ) 33.13 Equitable Adjustment (1) 153 — Outstanding at December 30, 2017 947 22.31 781 31.83 (1) Represents the adjustment made in conjunction with the special dividend issued on March 9, 2017 to equalize the intrinsic value of stock options pre- and post-distribution.

Accumulated Other Comprehensi41

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 30, 2017
Equity [Abstract]
Changes in AOCI by component, net of taxes and noncontrolling interest	The following table provides changes in AOCI by component, net of taxes and noncontrolling interest (amounts in parentheses indicate debits to AOCI): (In thousands) Cumulative Translation Adjustment Unrealized (Loss) Gain on Derivatives Pension/ Unrealized Gain on Equity Securities Attributable to Unconsol. Affiliates Total Balance at December 26, 2015 $ (24,773 ) $ (2,009 ) $ (28,429 ) $ 221 $ — $ (54,990 ) Other comprehensive (loss) income before reclassifications (25,192 ) 400 3,962 159 5,975 (14,696 ) Amounts reclassified from AOCI — 1,309 1,421 — — 2,730 Balance at December 31, 2016 (49,965 ) (300 ) (23,046 ) 380 5,975 (66,956 ) Other comprehensive income (loss) before reclassifications 15,579 (389 ) 1,394 (1 ) 895 17,478 Amounts reclassified from AOCI (3,777 ) 1,536 1,042 (379 ) — (1,578 ) Balance at December 30, 2017 $ (38,163 ) $ 847 $ (20,610 ) $ — $ 6,870 $ (51,056 )
Reclassification adjustments out of AOCI	Reclassification adjustments out of AOCI were as follows: Amount reclassified from AOCI (In thousands) 2017 2016 2015 Affected Line Item Unrealized losses on derivatives: Commodity contracts $ 1,309 $ 1,061 $ 4,486 Cost of goods sold Interest rate swap 851 361 372 Interest expense (624 ) (113 ) (1,310 ) Income tax benefit $ 1,536 $ 1,309 $ 3,548 Net of tax and noncontrolling interests Amortization of net loss and prior service cost on employee benefit plans $ 1,263 $ 1,942 $ 2,688 Selling, general, and administrative expense (221 ) (521 ) (719 ) Income tax benefit $ 1,042 $ 1,421 $ 1,969 Net of tax and noncontrolling interests Gain recognized upon sale of business $ (3,777 ) $ — $ — Selling, general, and administrative expense — — — Income tax expense $ (3,777 ) $ — $ — Net of tax and noncontrolling interests Sale of available-for-sale securities $ (611 ) $ — $ — Other income 232 — — Income tax expense $ (379 ) $ — $ — Net of tax and noncontrolling interests

Quarterly Financial Informati42

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 30, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly financial information (Unaudited)	( In thousands, except per share data) First Quarter Second Quarter Third Quarter Fourth Quarter 2017 Net sales $ 577,920 $ 614,266 $ 550,363 $ 523,524 Gross profit (2) 89,493 89,955 79,101 66,907 Consolidated net income (3) 30,455 27,833 22,754 5,969 (4) Net income attributable to Mueller Industries, Inc. 29,987 27,633 22,258 5,720 Basic earnings per share 0.53 0.49 0.39 0.10 Diluted earnings per share 0.52 0.48 0.39 0.10 Dividends per share 8.10 0.10 0.10 0.10 2016 Net sales $ 532,809 $ 544,071 $ 506,584 $ 472,158 Gross profit (2) 86,167 88,011 81,916 76,029 Consolidated net income (5) 28,665 28,259 26,062 (6) 16,768 (7) Net income attributable to Mueller Industries, Inc. 28,630 27,797 25,978 17,322 Basic earnings per share 0.51 0.49 0.46 0.31 Diluted earnings per share 0.50 0.49 0.45 0.30 Dividends per share 0.075 0.100 0.100 0.100 (1) The sum of quarterly amounts may not equal the annual amounts reported due to rounding. In addition, the earnings per share amounts are computed independently for each quarter, while the full year is based on the weighted average shares outstanding. (2) Gross profit is net sales less cost of goods sold, which excludes depreciation and amortization. (3) Includes income earned by Heatlink Group, acquired during Q2 2017. (4) Includes $1.1 million of pre-tax charges related to asset impairments, $4.3 million of interest expense on the Company’s Subordinated Debentures, and pre-tax environmental expense for non-operating properties of $6.2 million . (5) Includes income earned by Jungwoo-Mueller, acquired during Q2 2016. (6) Includes $3.0 million of pre-tax charges related to asset impairments. (7) Includes $3.8 million of pre-tax charges related to asset impairments.

Summary of Significant Accoun43

Summary of Significant Accounting Policies (Details) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 30, 2017USD ($)shares	Dec. 31, 2016USD ($)reportable_segmentshares	Dec. 26, 2015USD ($)reportable_segment
Noncontrolling Interest [Line Items]
Temporary investments	$ 0.6	$ 40.9
Restricted cash	$ 6.2	$ 9
Specified percentage over which unrecognized gains and losses are amortized	10.00%
Average remaining service period for the pension plans	9 years
Stock-based awards excluded from the computation of diluted earnings per share (in shares) | shares	20	190
Foreign currency transaction gains (losses)	$ (0.4)	$ 0.4	$ (1.7)
Number of reportable segments | reportable_segment		3	2
Tecumseh Products Holdings LLC [Member]
Noncontrolling Interest [Line Items]
Equity method investment, ownership percentage	50.00%
Second Unconsolidated Affiliate [Member]
Noncontrolling Interest [Line Items]
Equity method investment, ownership percentage	50.00%
Building [Member] | Minimum [Member]
Noncontrolling Interest [Line Items]
Property, plant and equipment, useful life	20 years
Building [Member] | Maximum [Member]
Noncontrolling Interest [Line Items]
Property, plant and equipment, useful life	40 years
Machinery and Equipment [Member] | Minimum [Member]
Noncontrolling Interest [Line Items]
Property, plant and equipment, useful life	5 years
Machinery and Equipment [Member] | Maximum [Member]
Noncontrolling Interest [Line Items]
Property, plant and equipment, useful life	20 years
Jungwoo-Mueller [Member]
Noncontrolling Interest [Line Items]
Non-controlling ownership interest	40.00%
Mueller-Xingrong [Member]
Noncontrolling Interest [Line Items]
Non-controlling ownership interest	49.50%

Acquisitions and Dispositions -

Acquisitions and Dispositions - Acquisition (Details) - USD ($) $ in Thousands	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

Acquisitions and Dispositions45

Acquisitions and Dispositions - Disposition (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 28, 2017	Jun. 21, 2017	Dec. 30, 2016	Jun. 01, 2015	Dec. 26, 2015	Jun. 27, 2015	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net (loss) income					$ (8,100)		$ (4,153)	$ 3,720
Gain (Loss) on Disposition of Business							1,491	0	$ 15,376
Proceeds from sale of assets, net of cash transferred							31,564	10,304	5,538
Mueller-Xingrong [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investment, ownership percentage		50.50%
Net sales of equity method investment							67,300	121,500	155,900
Net (loss) income							(9)	$ 62	$ 555
DWV Ontario Manufacturing Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Lease-back term				22 months
Total sales price of property				$ 20,200
Proceeds from sale of assets, net of cash transferred	$ 10,200		$ 5,000	5,000
Gain on sale of manufacturing assets						$ 15,400
Amount of diluted share after tax (in dollars per share)						$ 0.17
Carrying value of assets disposed				2,300
Goodwill allocated to disposal group				$ 2,400
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Mueller-Xingrong [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of interest		$ 18,300
Assets		56,800
Carrying value of the liabilities disposed		36,200
Cumulative translation loss		$ 3,800
Gain (Loss) on Disposition of Business							$ 1,500

Segment Information - Net Sales

Segment Information - Net Sales by Major Product Line (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Revenue from External Customer [Line Items]
Net sales	$ 2,266,073	$ 2,055,622	$ 2,100,002
Tube and Fittings [Member]
Revenue from External Customer [Line Items]
Net sales	1,260,105	1,072,242	1,053,761
Brass Rod and Forgings [Member]
Revenue from External Customer [Line Items]
Net sales	450,063	371,237	436,456
OEM Components, Tube & Assemblies [Member]
Revenue from External Customer [Line Items]
Net sales	272,567	327,327	342,651
Valves and Plumbing Specialties [Member]
Revenue from External Customer [Line Items]
Net sales	200,409	209,217	198,012
Other [Member]
Revenue from External Customer [Line Items]
Net sales	$ 82,929	$ 75,599	$ 69,122

Segment Information - Geographi

Segment Information - Geographic Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 2,266,073	$ 2,055,622	$ 2,100,002
Long-lived assets	304,321	295,231	280,224
Reportable Geographical Components [Member] | United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	1,556,825	1,400,893	1,519,456
Long-lived assets	238,752	223,099	223,398
Reportable Geographical Components [Member] | United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	231,039	197,039	240,823
Long-lived assets	17,661	15,978	19,982
Reportable Geographical Components [Member] | Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	280,140	237,162	97,967
Long-lived assets	21,327	18,928	20,460
Reportable Geographical Components [Member] | Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	121,295	149,875	162,664
Long-lived assets	25,973	36,722	15,863
Reportable Geographical Components [Member] | Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	76,774	70,653	79,092
Long-lived assets	$ 608	$ 504	$ 521

Segment Information - Segment I

Segment Information - Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Mar. 31, 2018	Dec. 30, 2017	Dec. 31, 2016	Oct. 01, 2016	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Net sales					$ 2,266,073	$ 2,055,622	$ 2,100,002
Cost of goods sold					1,940,617	1,723,499	1,809,702
Depreciation and amortization					33,944	35,133	34,608
Selling, general, and administrative expense					139,580	137,499	130,358
Gain on sale of businesses					(1,491)	0	(15,376)
Severance					0	0	3,442
Impairment charges		$ 1,100	$ 3,800	$ 3,000	1,466	6,778	0
Operating income					151,957	152,713	137,268
Interest expense					(19,502)	(7,387)	(7,667)
Environmental expense					(7,284)	(1,279)	(46)
Other income, net					1,801	1,983	2,234
Income before income taxes					126,972	146,030	131,789
Expenditures for long-lived assets					48,155	61,688	71,012
Impairment charges		1,100	3,800	$ 3,000	1,466	6,778	0
Segment assets		1,320,173	1,447,476		1,320,173	1,447,476	1,338,801
Intersegment Eliminations [Member]
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Net sales					(32,456)	(14,785)	(14,881)
Cost of goods sold					(34,368)	(16,282)	(14,688)
Depreciation and amortization					2,138	2,113	2,289
Selling, general, and administrative expense					43,452	46,458	43,383
Gain on sale of businesses					0		0
Severance							0
Impairment charges					0	0
Operating income					(43,678)	(47,074)	(45,865)
Impairment charges					0	0
Piping Systems [Member] | Operating Segments [Member]
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Net sales					1,564,950	1,429,589	1,436,689
Cost of goods sold					1,369,161	1,228,949	1,245,929
Depreciation and amortization					21,777	22,421	22,559
Selling, general, and administrative expense					74,479	68,218	66,903
Gain on sale of businesses					(1,491)		(15,376)
Severance							3,442
Impairment charges					1,500	6,115
Operating income					99,558	103,886	113,232
Expenditures for long-lived assets					18,124	56,286	41,900
Impairment charges					1,500	6,115
Segment assets		801,468	826,663		801,468	826,663	811,343
Industrial Metals [Member] | Operating Segments [Member]
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Net sales					602,131	521,060	567,467
Cost of goods sold					506,973	420,905	491,567
Depreciation and amortization					7,516	8,162	7,503
Selling, general, and administrative expense					11,890	13,162	10,955
Gain on sale of businesses					0		0
Severance							0
Impairment charges					0	663
Operating income					75,752	78,168	57,442
Expenditures for long-lived assets					5,322	3,302	16,603
Impairment charges					0	663
Segment assets		212,638	160,478		212,638	160,478	153,102
Climate [Member] | Operating Segments [Member]
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Net sales					131,448	119,758	110,727
Cost of goods sold					98,851	89,927	86,894
Depreciation and amortization					2,513	2,437	2,257
Selling, general, and administrative expense					9,759	9,661	9,117
Gain on sale of businesses					0		0
Severance							0
Impairment charges					0	0
Operating income					20,325	17,733	12,459
Expenditures for long-lived assets					2,191	2,045	12,373
Impairment charges					0	0
Segment assets		73,458	66,968		73,458	66,968	61,672
Corporate Segment [Member]
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Expenditures for long-lived assets					22,518	55	136
Segment assets		$ 232,609	$ 393,367		$ 232,609	$ 393,367	$ 312,684
Forecast [Member] | Aircraft [Member] | Held-for-sale [Member]
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Impairment charges	$ 3,300
Impairment charges	$ 3,300

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw materials and supplies	$ 108,397	$ 57,387
Work-in-process	46,158	42,227
Finished goods	180,143	149,288
Valuation reserves	(6,797)	(6,889)
Inventories	$ 327,901	$ 242,013

Inventories, Additional Informa

Inventories, Additional Information (Details) - USD ($) $ in Millions	Dec. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
LIFO inventory amount	$ 26.5		$ 14.4
FIFO cost of inventories	111		76.6
Average cost basis inventories	43.9		43.8
Liquidation of LIFO inventory layers deferred			2.5
Liquidation of LIFO inventory layers			3.3
Excess inventory		$ 38.9
FIFO value of inventory consigned to others	$ 4.4		$ 2.5

Consolidated Financial Statem51

Consolidated Financial Statement Details (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 30, 2017	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Other Current Liabilities [Abstract]
Accrued discounts and allowances	$ 39,500	$ 39,500	$ 40,400
Taxes payable, current	9,200	9,200	4,600
Accrued interest	5,900	5,900	300
Environmental expense, non operating properties	$ 6,200	4,300	800
Other (Expense) Income, Net [Abstract]
Interest income		684	1,185	$ 1,029
Other		1,117	798	1,205
Other income, net		$ 1,801	$ 1,983	$ 2,234

Derivative Instruments and He52

Derivative Instruments and Hedging Activities - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Restricted cash in other current assets as collateral related to open derivative contracts	$ 5.3	$ 1.4
Commodity Contract [Member]
Derivative [Line Items]
Deferred net gains (losses), net of tax, included in AOCI	0.7
Cash Flow Hedging [Member] | Commodity Contract [Member] | Long [Member]
Derivative [Line Items]
Open future contracts to purchase copper	$ 19.6
Time period for open copper future contract	12 months
Fair value of future contracts with gain (loss) position	$ 1
Fair Value Hedging [Member] | Commodity Contract [Member] | Short [Member]
Derivative [Line Items]
Fair value of future contracts with gain (loss) position	(3.2)
Open future contracts to sell copper	$ 85.3
Time period for open copper future contract sales	5 months

Derivative Instruments and He53

Derivative Instruments and Hedging Activities - Derivative Assets and Liabilities (Details) - Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Assets fair value	$ 1,009	$ 865
Liabilities fair value	(3,155)	(1,143)
Other Current Asset [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Other current assets: Gain positions	1,014	1,013
Other current assets: Loss positions	(5)	(148)
Other Current Asset [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Other current assets: Loss positions	0	0
Other Current Liabilities [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Other current liability: Gain positions	55	564
Other current liability: Loss positions	(3,210)	(920)
Other Current Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Other current liability: Loss positions	$ 0	$ (787)

Derivative Instruments and He54

Derivative Instruments and Hedging Activities - Effects on Statement of Income and Amounts Recognized In and Reclassified From AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) Gain Recognized in AOCI (Effective Portion), Net of Tax	$ (389)	$ 400
Loss Reclassified from AOCI (Effective Portion), Net of Tax	1,536	1,309
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) gain on commodity contracts (nonqualifying)	(6,078)	4,068
Commodity Contract [Member] | Fair Value Hedging [Member] | Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on the derivatives in designated and qualifying fair value hedges	(724)	(420)
Commodity Contract [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) Gain Recognized in AOCI (Effective Portion), Net of Tax	(574)	308
Commodity Contract [Member] | Cash Flow Hedging [Member] | Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Loss Reclassified from AOCI (Effective Portion), Net of Tax	990	1,078
Inventories [Member] | Fair Value Hedging [Member] | Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on the derivatives in designated and qualifying fair value hedges	625	382
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) Gain Recognized in AOCI (Effective Portion), Net of Tax	0	305
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Loss Reclassified from AOCI (Effective Portion), Net of Tax	546	231
Other [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) Gain Recognized in AOCI (Effective Portion), Net of Tax	185	(213)
Other [Member] | Cash Flow Hedging [Member] | Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Loss Reclassified from AOCI (Effective Portion), Net of Tax	$ 0	$ 0

Property, Plant, and Equipmen55

Property, Plant, and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 822,208	$ 802,530
Less accumulated depreciation	(517,887)	(507,299)
Property, plant, and equipment, net	304,321	295,231
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	18,740	19,928
Building [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	144,527	144,914
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	649,667	607,344
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 9,274	$ 30,344

Goodwill and Other Intangible56

Goodwill and Other Intangible Assets (Details) - USD ($)	12 Months Ended
	Dec. 30, 2017		Dec. 31, 2016		Dec. 26, 2015
Goodwill [Roll Forward]
Goodwill			$ 169,657,000
Accumulated impairment charges, beginning of year			(49,405,000)
Goodwill, net, beginning balance	$ 123,993,000		120,252,000
Additions	3,852,000	[1]	4,601,000	[2]
Currency translation	2,448,000		(860,000)
Goodwill	179,698,000				$ 169,657,000
Accumulated impairment loss, end of year	(49,405,000)				(49,405,000)
Goodwill, net, ending balance	130,293,000		123,993,000		120,252,000
Impairment charges	0		0		0
Great Lakes Copper, Inc [Member]
Goodwill [Roll Forward]
Purchase price allocation adjustments	4,100,000
Jungwoo-Mueller [Member]
Goodwill [Roll Forward]
Purchase price allocation adjustments	200,000
Piping Systems [Member]
Goodwill [Roll Forward]
Goodwill			156,387,000
Accumulated impairment charges, beginning of year			(40,552,000)
Goodwill, net, beginning balance	119,576,000		115,835,000
Additions	3,852,000	[1]	4,601,000	[2]
Currency translation	2,448,000		(860,000)
Goodwill	166,428,000				156,387,000
Accumulated impairment loss, end of year	(40,552,000)				(40,552,000)
Goodwill, net, ending balance	125,876,000		119,576,000		115,835,000
Industrial Metals [Member]
Goodwill [Roll Forward]
Goodwill			8,854,000
Accumulated impairment charges, beginning of year			(8,853,000)
Goodwill, net, beginning balance	1,000		1,000
Additions	0	[1]	0	[2]
Currency translation	0		0
Goodwill	8,854,000				8,854,000
Accumulated impairment loss, end of year	(8,853,000)				(8,853,000)
Goodwill, net, ending balance	1,000		1,000		1,000
Climate [Member]
Goodwill [Roll Forward]
Goodwill			4,416,000
Accumulated impairment charges, beginning of year			0
Goodwill, net, beginning balance	4,416,000		4,416,000
Additions	0	[1]	0	[2]
Currency translation	0		0
Goodwill	4,416,000				4,416,000
Accumulated impairment loss, end of year	0				0
Goodwill, net, ending balance	$ 4,416,000		$ 4,416,000		$ 4,416,000
[1]	Includes finalization of the purchase price allocation adjustment for Jungwoo-Mueller of $0.2 million.
[2]	Includes finalization of the purchase price allocation adjustment for Great Lakes of $4.1 million.

Goodwill and Other Intangible57

Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Carrying amount of intangible assets [Abstract]
Net Carrying Amount	$ 42,008
Amortization	3,100	$ 4,300	$ 4,100
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2,018	3,338
2,019	3,253
2,020	3,017
2,021	2,747
2,022	2,851
Thereafter	26,802
Net Carrying Amount	42,008
Customer relationships [Member]
Carrying amount of intangible assets [Abstract]
Gross Carrying Amount	36,518	29,833
Accumulated Amortization	(4,644)	(2,845)
Net Carrying Amount	31,874	26,988
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	31,874	26,988
Non-compete agreements [Member]
Carrying amount of intangible assets [Abstract]
Gross Carrying Amount	2,834	5,926
Accumulated Amortization	(1,497)	(4,063)
Net Carrying Amount	1,337	1,863
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	1,337	1,863
Patents and technology [Member]
Carrying amount of intangible assets [Abstract]
Gross Carrying Amount	7,673	5,922
Accumulated Amortization	(1,868)	(1,179)
Net Carrying Amount	5,805	4,743
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	5,805	4,743
Trade names and licenses [Member]
Carrying amount of intangible assets [Abstract]
Gross Carrying Amount	4,977	4,087
Accumulated Amortization	(1,575)	(1,032)
Net Carrying Amount	3,402	3,055
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	3,402	3,055
Other [Member]
Carrying amount of intangible assets [Abstract]
Gross Carrying Amount	213	213
Accumulated Amortization	(623)	(694)
Net Carrying Amount	(410)	(481)
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	(410)	(481)
Other intangible assets [Member]
Carrying amount of intangible assets [Abstract]
Gross Carrying Amount	52,215	45,981
Accumulated Amortization	(10,207)	(9,813)
Net Carrying Amount	42,008	36,168
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	$ 42,008	$ 36,168

Investment in Unconsolidated 58

Investment in Unconsolidated Affiliates (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 26, 2015	Dec. 30, 2017	Dec. 31, 2016
Balance sheet data [Abstract]
Current assets		$ 246,127	$ 244,323
Noncurrent assets		139,200	130,400
Current liabilities		174,710	148,806
Noncurrent liabilities		58,334	71,681
Income statement data [Abstract]
Net sales		556,600	579,400
Gross profit		75,600	79,600
Net (loss) income	$ (8,100)	$ (4,153)	$ 3,720

Investment in Unconsolidated 59

Investment in Unconsolidated Affiliates - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 26, 2015	Dec. 30, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Gain resulted from the allocation of the purchase price included in Joint Venture's net income			$ 17,100
Restructuring and impairment charges	$ 5,300
Net (loss) income	$ (8,100)	$ (4,153)	$ 3,720
Tecumseh Products Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Interest in joint venture		50.00%
Second Unconsolidated Affiliate [Member]
Schedule of Equity Method Investments [Line Items]
Interest in joint venture		50.00%
Cayan Ventures and Bahrain Mumtalakat Holding Company [Member]
Schedule of Equity Method Investments [Line Items]
Interest in joint venture		40.00%
Cash invested in joint venture		$ 3,900

New Markets Tax Credit Transa60

New Markets Tax Credit Transactions (Details) $ in Millions	12 Months Ended
	Dec. 30, 2017USD ($)
Variable Interest Entity [Line Items]
Percentage of qualifying investments on tax credits	39.00%
Aggregate principal amount	$ 13.7
Percentage of aggregate principal amount, leverage loan	1.00%
Percentage of recapture to the tax credits	100.00%
Compliance period	7 years
Wells Fargo [Member]
Variable Interest Entity [Line Items]
Contribution to investment fund	$ 6.6

Debt (Details)

Debt (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt, gross	$ 466,247	$ 228,321
Less debt issuance costs	(1,175)	(957)
Less current portion of debt	(16,480)	(13,655)
Long-term debt	448,592	213,709
Subordinated Debt [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 284,536	0
Debt, stated interest rate	6.00%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 160,000	200,000
Debt, stated interest rate	3.06%
Jungwoo Mueller Line of Credit Due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 5,119	4,724
Debt, stated interest rate	2.72%
Jungwoo Mueller Line of Credit Due 2017 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 8,648	7,990
Debt, stated interest rate	3.19%
2001 Series IRB's With Interest at 1.23% Due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 3,250	4,250
Debt, stated interest rate	2.22%
Mueller Xingrong Credit Facility [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 0	3,048
Other [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 4,694	$ 8,309

Debt - Additional Information (

Debt - Additional Information (Details)	Mar. 09, 2017USD ($)$ / shares	Dec. 30, 2017USD ($)	Dec. 30, 2017KRW (₩)
Debt Instrument [Line Items]
Cash dividend (in dollars per share) | $ / shares	$ 3
Cash dividend, subordinated debentures (in dollars per share) | $ / shares	$ 5
Decrease in stockholders' equity	$ 458,700,000
Increase in long term debt	284,500,000
Decrease in cash	$ 174,200,000
Subordinated Debt [Member]
Debt Instrument [Line Items]
Debt, stated interest rate		6.00%	6.00%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity		$ 350,000,000
Credit Agreement [Member]
Debt Instrument [Line Items]
Outstanding letters of credit		8,400,000
Jungwoo-Mueller [Member]
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity		$ 27,500,000	₩ 29,900,000,000
Minimum [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Credit facility commitment fee		0.15%
Maximum [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Credit facility commitment fee		0.30%
LIBOR [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		1.50%
LIBOR [Member] | Minimum [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		1.125%
LIBOR [Member] | Maximum [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		1.625%
Base Rate [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		0.50%
Base Rate [Member] | Minimum [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		0.125%
Base Rate [Member] | Maximum [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		0.625%

Debt - Redemption Schedule (Det

Debt - Redemption Schedule (Details) - Subordinated Debt [Member]	12 Months Ended
	Dec. 30, 2017
2017 [Member]
Debt Instrument [Line Items]
Redemption Price	106.00%
2018 [Member]
Debt Instrument [Line Items]
Redemption Price	105.00%
2019 [Member]
Debt Instrument [Line Items]
Redemption Price	104.00%
2020 [Member]
Debt Instrument [Line Items]
Redemption Price	103.00%
2021 [Member]
Debt Instrument [Line Items]
Redemption Price	102.00%
2022 and thereafter [Member]
Debt Instrument [Line Items]
Redemption Price	100.00%

Debt - Aggregate Annual Maturit

Debt - Aggregate Annual Maturities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Long-term Debt, Fiscal Year Maturity [Abstract]
2,018	$ 16,480
2,019	1,222
2,020	1,222
2,021	160,472
2,022	222
Thereafter	286,629
Long-term debt	466,247
Interest paid	$ 13,800	$ 7,100	$ 8,100

Debt - Net Interest Expense (De

Debt - Net Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Debt Disclosure [Abstract]
Interest expense	$ 19,716	$ 7,749	$ 8,335
Capitalized interest	(214)	(362)	(668)
Net interest expense	$ 19,502	$ 7,387	$ 7,667

Benefit Plans (Details)

Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Change in fair value of plan assets:
Actuarial net loss	$ 1,500
Prior service credit	$ (900)
Payable maximum period to be considered current	12 months
Funded status of the plans recognized [Abstract]
Long-term liability	$ (11,606)	$ (14,890)
Weighted average assumptions in net periodic benefit calculations [Abstract]
Ultimate health care cost trend rate	3.00%
Minimum [Member]
Weighted average assumptions in net periodic benefit calculations [Abstract]
Annual assumed rate of increase in the per capita cost of covered benefits	6.60%
Maximum [Member]
Weighted average assumptions in net periodic benefit calculations [Abstract]
Annual assumed rate of increase in the per capita cost of covered benefits	10.10%
Pension Plan [Member]
Change in benefit obligation [Roll Forward]
Obligation at beginning of year	$ 178,736	192,761
Service cost	128	532	$ 803
Interest cost	6,344	7,553	8,032
Actuarial loss (gain)	4,688	9,399
Plan amendments	0	0
Benefit payments	(10,171)	(17,572)
Settlement charge	0	0
Foreign currency translation adjustment	7,041	(13,937)
Obligation at end of year	186,766	178,736	192,761
Change in fair value of plan assets:
Fair value of plan assets at beginning of year	169,140	176,077
Actual return on plan assets	19,175	19,319
Employer contributions	2,271	2,377
Benefit payments	(10,171)	(17,572)
Foreign currency translation adjustment	5,921	(11,061)
Fair value of plan assets at end of year	186,336	169,140	176,077
Underfunded status at end of year	(430)	(9,596)
Incremental benefit payments		7,000
Settlement charge	0	1,214	0
Unrecognized net actuarial loss	34,627	39,986
Unrecognized prior service credit	0	0
Funded status of the plans recognized [Abstract]
Long-term asset	9,894	4,442
Current liability	0	0
Long-term liability	(10,324)	(14,038)
Total underfunded status	(430)	(9,596)
Components of net periodic benefit cost [Abstract]
Service cost	128	532	803
Interest cost	6,344	7,553	8,032
Expected return on plan assets	(9,374)	(9,615)	(10,289)
Amortization of net (gain) loss	2,206	2,898	2,710
Settlement charge	0	1,214	0
Net periodic benefit (income) cost	$ (696)	$ 2,582	$ 1,256
Weighted average assumptions in benefit obligations calculations [Abstract]
Discount rate	3.22%	3.61%
Expected long-term return on plan assets	5.27%	5.56%
Rate of inflation	3.30%	3.30%
Weighted average assumptions in net periodic benefit calculations [Abstract]
Discount rate	3.61%	4.02%	4.03%
Expected long-term return on plan assets	5.56%	5.59%	5.58%
Rate of inflation	3.30%	3.20%	3.10%
Other Postretirement Benefit Plan [Member]
Change in benefit obligation [Roll Forward]
Obligation at beginning of year	$ 15,274	$ 15,843
Service cost	235	232	$ 363
Interest cost	599	594	1,005
Actuarial loss (gain)	923	(249)
Plan amendments	0	43
Benefit payments	(883)	(1,023)
Settlement charge	(209)	0
Foreign currency translation adjustment	468	(166)
Obligation at end of year	16,407	15,274	15,843
Change in fair value of plan assets:
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	883	1,023
Benefit payments	(883)	(1,023)
Foreign currency translation adjustment	0	0
Fair value of plan assets at end of year	0	0	0
Underfunded status at end of year	(16,407)	(15,274)
Settlement charge	17	0	0
Unrecognized net actuarial loss	1,540	614
Unrecognized prior service credit	(7,289)	(8,180)
Funded status of the plans recognized [Abstract]
Long-term asset	0	0
Current liability	(1,070)	(1,128)
Long-term liability	(15,337)	(14,146)
Total underfunded status	(16,407)	(15,274)
Components of net periodic benefit cost [Abstract]
Service cost	235	232	363
Interest cost	599	594	1,005
Amortization of net (gain) loss	(42)	(60)	(28)
Amortization of prior service (credit) cost	(901)	(896)	6
Settlement charge	17	0	0
Net periodic benefit (income) cost	$ (92)	$ (130)	$ 1,346
Weighted average assumptions in benefit obligations calculations [Abstract]
Discount rate	3.89%	4.21%
Rate of compensation increases	5.00%	5.00%
Weighted average assumptions in net periodic benefit calculations [Abstract]
Discount rate	4.21%	4.25%	4.33%
Rate of compensation increases	5.00%	5.00%	5.00%
U.K Plan [Member]
Change in fair value of plan assets:
Percent of above benefit obligation on company sponsored UK pension plan	44.00%	42.00%
Percent above plan assets on company sponsored UK pension plan	39.00%	36.00%

Benefit Plans - Pension Assets

Benefit Plans - Pension Assets by Percentage (Details) - Pension Plan [Member]	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Asset category [Abstract]
Total plan assets	100.00%	100.00%
Expected long-term rate of return on plan assets	5.27%	5.56%
Equity Securities [Member]
Asset category [Abstract]
Total plan assets	46.00%	47.00%
Fixed Income Funds [Member]
Asset category [Abstract]
Total plan assets	48.00%	48.00%
Cash and Cash Equivalents [Member]
Asset category [Abstract]
Total plan assets	3.00%	3.00%
Alternative Investments [Member]
Asset category [Abstract]
Total plan assets	3.00%	2.00%
Minimum [Member] | Fixed Income Funds [Member]
Asset category [Abstract]
Total plan assets	60.00%
Maximum [Member] | Equity Securities [Member]
Asset category [Abstract]
Total plan assets	30.00%
Maximum [Member] | Alternative Investments [Member]
Asset category [Abstract]
Total plan assets	5.00%

Benefit Plans - Pension Asset68

Benefit Plans - Pension Assets by Fair Value Level (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	$ 186,336	$ 169,140
Approximate percentage of common stock invested in major industry	91.00%	90.00%
Approximate percentage of mutual funds actively managed	66.00%	68.00%
Approximate percentage of mutual funds indexed funds	34.00%	32.00%
Percentage of mutual funds' assets invested in U.S equities	5.00%	5.00%
Percent of mutual funds assets invested in non US equities	41.00%	38.00%
Percent of mutual funds assets invested in US fixed income securities	52.00%	54.00%
Percent of mutual funds assets invested in non US fixed income securities	2.00%	3.00%
Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	$ 24,889	$ 28,418
Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	156,442	136,027
Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	5,005	4,695
Cash and Cash Equivalents [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	5,364	4,245
Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	5,364	4,245
Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Cash and Cash Equivalents [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Common Stock [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	11,113	18,601
Common Stock [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	11,113	18,601
Common Stock [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Common Stock [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Mutual Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	164,854	141,599
Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	8,412	5,572
Mutual Funds [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	156,442	136,027
Mutual Funds [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Limited Partnerships [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	5,005	4,695
Limited Partnerships [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Limited Partnerships [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Limited Partnerships [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	$ 5,005	$ 4,695

Benefit Plans - Assets of the P

Benefit Plans - Assets of the Plan Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Details) - Limited Partnerships [Member] $ in Thousands	12 Months Ended
	Dec. 30, 2017USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 4,695
Redemptions	(283)
Subscriptions	273
Net appreciation in fair value	320
Ending balance	$ 5,005

Benefit Plans - Contributions a

Benefit Plans - Contributions and Benefit Payments, Multiemployer Plan, 401(k) Plans and UMWA Benefit Plans (Details) $ in Thousands	12 Months Ended
	Dec. 30, 2017USD ($)bargain_agreement	Dec. 31, 2016USD ($)	Dec. 26, 2015USD ($)
IAM Plan Trusts [Abstract]
Number of collective bargaining agreements | bargain_agreement	2
Pension contributions under the I.A.M. pension plan trusts	$ 1,100	$ 1,100	$ 1,100
Maximum percentage of employer contributions	5.00%
401 (k) Plan [Abstract]
Compensation expense for the Company's matching contribution	$ 5,100	5,200	4,200
Contributions to UMWA 1992 Benefit Plan	182	$ 197	$ 214
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Company's expected contribution to benefit plans in next fiscal year	1,000
Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Company's expected contribution to benefit plans in next fiscal year	$ 1,200

Benefit Plans - Contributions71

Benefit Plans - Contributions and Benefit Payments (Details) $ in Thousands	Dec. 30, 2017USD ($)
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,018	$ 10,423
2,019	10,398
2,020	10,329
2,021	10,246
2,022	10,182
2023-2027	49,965
Total	101,543
Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,018	1,177
2,019	1,056
2,020	1,277
2,021	1,129
2,022	1,157
2023-2027	6,154
Total	$ 11,950

Commitments and Contingencies -

Commitments and Contingencies - Environmental (Details) $ in Millions	1 Months Ended		12 Months Ended			36 Months Ended
	Jan. 31, 2018USD ($)unilateral_administrative_orders	Sep. 30, 2014USD ($)property	Dec. 30, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 26, 2015USD ($)	Dec. 30, 2017USD ($)	Dec. 30, 2017smelter_site	Dec. 30, 2017Party
Site Contingency [Line Items]
Environmental expense			$ 7.5	$ 0.9	$ 0.1
Environmental reserves			28	$ 21.9		$ 28
Expected environmental expenditures for 2018			4.3			4.3
Expected environmental expenditures for 2019			2.2			2.2
Expected environmental expenditures for 2020			2.1			2.1
Expected environmental expenditures for 2021			0.6			0.6
Expected environmental expenditures for 2022			0.6			0.6
Expected environmental expenditures after 2022			18.2			18.2
Lead Refinery Site [Member]
Lead Refinery Site [Abstract]
Site contingency, financial guarantee			$ 1			1
Non-Operating Properties [Member] | Lead Refinery Site [Member]
Site Contingency [Line Items]
Environmental expense						0.6
Estimated number of years until mitigation resolution			19 years
Lead Refinery Site [Abstract]
EPA's estimated cost of site remediation		$ 26
Number of surrounding properties | property		300
Non-Operating Properties [Member] | Lead Refinery Site [Member] | Minimum [Member]
Site Contingency [Line Items]
Mitigation estimates			$ 1.8
Non-Operating Properties [Member] | Lead Refinery Site [Member] | Maximum [Member]
Site Contingency [Line Items]
Mitigation estimates			3
Non-Operating Properties [Member] | Southeast Kansas Sites [Member]
Site Contingency [Line Items]
Environmental reserves			$ 5.6			5.6
Number of parties involved in settlement negotiations							3	2
Non-Operating Properties [Member] | Shasta Area Mine Sites [Member]
Site Contingency [Line Items]
Period of permit, implementation of Best Management Practices			10 years
Environmental spending						$ 1.2
Estimated number of years until mitigation resolution			30 years
Non-Operating Properties [Member] | Shasta Area Mine Sites [Member] | Minimum [Member]
Site Contingency [Line Items]
Mitigation estimates			$ 12.8
Non-Operating Properties [Member] | Shasta Area Mine Sites [Member] | Maximum [Member]
Site Contingency [Line Items]
Mitigation estimates			$ 17.6
Operating Properties [Member] | Mueller Copper Tube Products, Inc. [Member]
Site Contingency [Line Items]
Estimated number of years until mitigation resolution			8 years
Operating Properties [Member] | Mueller Copper Tube Products, Inc. [Member] | Minimum [Member]
Site Contingency [Line Items]
Mitigation estimates			$ 0.8
Operating Properties [Member] | Mueller Copper Tube Products, Inc. [Member] | Maximum [Member]
Site Contingency [Line Items]
Mitigation estimates			$ 1.2
Subsequent Event [Member] | Lead Refinery NPL Site [Member]
Site Contingency [Line Items]
Environmental reserves	$ 4.5
Lead Refinery Site [Abstract]
Number of UAOs issued | unilateral_administrative_orders	2
Site contingency, total costs	$ 25
Site contingency, amount agreed upon to pay PRPs for past costs	$ 2

Commitments and Contingencies73

Commitments and Contingencies - United States Department of Commerce Antidumping Review (Details) $ in Millions	Oct. 05, 2016individual	Nov. 27, 2015USD ($)	Oct. 31, 2008Import_entry	Apr. 19, 2010
United States Department of Commerce Antidumping Review [Member]
Loss Contingencies [Line Items]
Assignment of antidumping duty rate on U.S. imports by Company subsidiaries				48.33%
Payment request for interest and duties | $		$ 3
Number of import entries | Import_entry			795
Equal Employment Opportunity Commission Matter [Member]
Loss Contingencies [Line Items]
Number of identified class individuals	20
Number of unidentified class individuals	150

Commitments and Contingencies74

Commitments and Contingencies - Leases (Details) - Facilities Vehicles and Equipment [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Operating Leased Assets [Line Items]
Lease payments scheduled for 2018	$ 7
Lease payments scheduled for 2019	5.2
Lease payments scheduled for 2020	4.4
Lease payments scheduled for 2021	3.5
Lease payments scheduled for 2022	3.1
Lease payments scheduled after 2022	17.3
Lease expense	$ 11.9	$ 11.6	$ 9.7

Income Taxes - Components of In

Income Taxes - Components of Income Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Income Tax Disclosure [Abstract]
Domestic	$ 76,876	$ 103,576	$ 121,614
Foreign	50,096	42,454	10,175
Income before income taxes	$ 126,972	$ 146,030	$ 131,789

Income Taxes - Components of 76

Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Current tax expense:
Federal	$ 28,584	$ 32,262	$ 50,272
Foreign	10,219	5,667	4,042
State and local	2,241	3,210	4,886
Current tax expense	41,044	41,139	59,200
Deferred tax (benefit) expense:
Federal	(1,764)	2,004	(13,739)
Foreign	1,118	5,099	(1,180)
State and local	(2,514)	(105)	(899)
Deferred tax (benefit) expense	(3,160)	6,998	(15,818)
Income tax expense	$ 37,884	$ 48,137	$ 43,382

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Income Tax Disclosure [Abstract]
Increase in tax expense due to one-time transition tax liability	$ 12,900
Increase in income tax expense recorded for its one-time transition tax liability, effect on diluted earnings per share (in dollars per share)	$ 0.22
Income tax benefit as a result of the remeasurement of deferred tax balance	$ 12,100
Income tax benefit as a result of the remeasurement of deferred tax balance, effect on diluted earnings per share (in dollars per share)	$ 0.21
Adjustment to deferred tax liability	$ 0	$ 0	$ (4,218)
Permanent adjustment to deferred tax liabilities (in dollars per share)			$ 0.07
Income tax expense related to penalties and interest	0	0	$ 0
State income tax credit carryforwards with expiration	4,500
Other state income tax credit carryforwards with unlimited life	12,600
State net operating loss carryforwards with potential tax benefits	13,500
Valuation allowances	17,600
Foreign tax credits	5,100
Federal and foreign tax attributes with potential tax benefits	5,900
Income taxes paid	$ 42,500	$ 40,100	$ 49,900

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Income Tax Disclosure [Abstract]
Expected income tax expense	$ 44,440	$ 51,110	$ 46,126
State and local income tax, net of federal benefit	1,135	1,982	2,673
Effect of foreign statutory rate different from U.S. and other foreign adjustments	(6,026)	(4,092)	(654)
U.S. production activities deduction	(1,575)	(3,063)	(3,500)
Goodwill disposition	0	0	646
Investment in unconsolidated affiliates	216	1,030	0
Permanent adjustment to deferred tax liabilities	0	0	(4,218)
Benefit of stock-based compensation deductions	(2,160)	(656)	0
Effect of tax on accumulated foreign earnings	12,893	0	0
Effect of tax rate change on net deferred tax liability balance	(12,067)	0	0
Other, net	1,028	1,826	2,309
Income tax expense	$ 37,884	$ 48,137	$ 43,382

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Deferred tax assets [Abstract]
Inventories	$ 10,598	$ 15,483
Other postretirement benefits and accrued items	9,239	13,180
Other reserves	9,029	9,821
Federal and foreign tax attributes	11,936	5,813
State tax attributes, net of federal benefit	29,720	22,572
Stock-based compensation	2,102	2,416
Basis difference in unconsolidated affiliates	0	211
Total deferred tax assets	72,624	69,496
Less valuation allowance	(30,316)	(18,681)
Deferred tax assets, net of valuation allowance	42,308	50,815
Deferred tax liabilities:
Property, plant, and equipment	43,972	52,319
Pension	3,841	4,633
Basis difference in unconsolidated affiliates	203	0
Total deferred tax liabilities	48,016	56,952
Net deferred tax liabilities	$ (5,708)	$ (6,137)

Equity (Details)

Equity (Details)	Dec. 30, 2017shares
Equity [Abstract]
Authorization to repurchase shares of common stock (in shares)	20,000,000
Shares repurchased (in shares)	4,700,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 7.5	$ 6.4	$ 6.2
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of options granted (in dollars per share)	$ 9.38	$ 7.87	$ 7.58
Total intrinsic value of options exercised	$ 10.2	$ 2.5	$ 3.1
Fair value of options vested	1	0.3	0.8
Aggregate intrinsic value of all outstanding options	$ 12.4
Weighted average remaining contractual term of all outstanding options	6 years 2 months
Outstanding options, exercisable (in shares)	476
Aggregate intrinsic value of current exercisable shares	$ 8.5
Weighted average exercise price (in dollars per share)	$ 17.57
Weighted average remaining contractual term	4 years 6 months 18 days
Compensation for stock awards not yet recognized	$ 1.9
Compensation recognition period	3 years 6 months 18 days
Shares available for future issuance (in shares)	700
Employee Stock Option [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options vesting period	5 years
Stock options expiration period	10 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of options vested	$ 3.5	$ 4.7	$ 4.8
Compensation for stock awards not yet recognized	$ 15.8
Compensation recognition period	3 years 2 months 24 days
Granted (in dollars per share)	$ 30.97	$ 34.04	$ 32.54
Aggregate intrinsic value	$ 27.7

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions in Determining Fair Value of Options Granted (Details) - Employee Stock Option [Member]	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	7 years 8 months 12 days	6 years 8 months 12 days	5 years 6 months
Expected price volatility	28.90%	25.60%	26.20%
Risk-free interest rate	2.10%	1.60%	1.70%
Dividend yield	1.30%	1.00%	0.90%

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Options and Restricted Stock Awards (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Employee Stock Option [Member]
Options outstanding [Roll Forward]
Beginning balance (in shares)	1,034
Granted (in shares)	165
Exercised (in shares)	(395)
Forfeited (in shares)	(10)
Equitable Adjustment (in shares)	(153)
Ending balance (in shares)	947	1,034
Weighted average exercise price [Roll Forward]
Beginning balance (in dollars per share)	$ 21.24
Granted (in dollars per share)	31.04
Exercised (in dollars per share)	12.10
Forfeited (in dollars per share)	26.68
Ending balance (in dollars per share)	$ 22.31	$ 21.24
Restricted Stock [Member]
Restricted stock [Roll Forward]
Beginning balance (in shares)	709
Granted (in shares)	209
Exercised (in shares)	(135)
Forfeited (in shares)	(2)
Equitable Adjustment (in shares)	0
Ending balance (in shares)	781	709
Weighted average grant date fair value [Abstract]
Beginning balance (in dollars per share)	$ 31.02
Granted (in dollars per share)	30.97	$ 34.04	$ 32.54
Exercised (in dollars per share)	26.22
Forfeited (in dollars per share)	33.13
Ending balance (in dollars per share)	$ 31.83	$ 31.02

Accumulated Other Comprehensi84

Accumulated Other Comprehensive Income (Loss) - Changes in AOCI by Component (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Changes in accumulated other comprehensive income [Roll Forward]
Balance at beginning of year	$ 936,437
Other comprehensive (loss) income before reclassifications	17,478	$ (14,696)
Amounts reclassified from AOCI	(1,578)	2,730
Balance at end of year	536,028	936,437
Cumulative Translation Adjustment [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Balance at beginning of year	(49,965)	(24,773)
Other comprehensive (loss) income before reclassifications	15,579	(25,192)
Amounts reclassified from AOCI	(3,777)	0
Balance at end of year	(38,163)	(49,965)	$ (24,773)
Unrealized Losses on Derivatives [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Balance at beginning of year	(300)	(2,009)
Other comprehensive (loss) income before reclassifications	(389)	400
Amounts reclassified from AOCI	1,536	1,309
Balance at end of year	847	(300)	(2,009)
Minimum Pension/OPEB Liability Adjustment [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Balance at beginning of year	(23,046)	(28,429)
Other comprehensive (loss) income before reclassifications	1,394	3,962
Amounts reclassified from AOCI	1,042	1,421	1,969
Balance at end of year	(20,610)	(23,046)	(28,429)
Unrealized Gains on Equity Investments [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Balance at beginning of year	380	221
Other comprehensive (loss) income before reclassifications	(1)	159
Amounts reclassified from AOCI	(379)	0
Balance at end of year	0	380	221
Attributable to Unconsolidated Affiliates [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Balance at beginning of year	5,975	0
Other comprehensive (loss) income before reclassifications	895	5,975
Amounts reclassified from AOCI	0	0
Balance at end of year	6,870	5,975	0
AOCI Attributable to Parent [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Balance at beginning of year	(66,956)	(54,990)	(42,923)
Balance at end of year	$ (51,056)	$ (66,956)	$ (54,990)

Accumulated Other Comprehensi85

Accumulated Other Comprehensive Income (Loss) - Reclassification Adjustments out of AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Reclassification Adjustments out of AOCI [Abstract]
Cost of goods sold	$ (1,940,617)	$ (1,723,499)	$ (1,809,702)
Interest expense	(19,502)	(7,387)	(7,667)
Income tax expense	(37,884)	(48,137)	(43,382)
Other income	1,801	1,983	2,234
Net of tax and noncontrolling interests	(1,578)	2,730
Selling, general, and administrative expense	(139,580)	(137,499)	(130,358)
Unrealized Losses on Derivatives [Member] | Amount Reclassified from AOCI [Member]
Reclassification Adjustments out of AOCI [Abstract]
Cost of goods sold	1,309	1,061	4,486
Interest expense	851	361	372
Income tax expense	(624)	(113)	(1,310)
Consolidated net income	1,536	1,309	3,548
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Reclassification Adjustments out of AOCI [Abstract]
Selling, general, and administrative expense	1,263	1,942	2,688
Income tax benefit	(221)	(521)	(719)
Net of tax and noncontrolling interests	1,042	1,421	1,969
Gain Recognized Upon Sale of Business [Member] | Amount Reclassified from AOCI [Member]
Reclassification Adjustments out of AOCI [Abstract]
Income tax expense	0	0	0
Consolidated net income	(3,777)	0	0
Selling, general, and administrative expense	(3,777)	0	0
Unrealized Gains on Equity Investments [Member]
Reclassification Adjustments out of AOCI [Abstract]
Net of tax and noncontrolling interests	(379)	0
Unrealized Gains on Equity Investments [Member] | Amount Reclassified from AOCI [Member]
Reclassification Adjustments out of AOCI [Abstract]
Income tax expense	232	0	0
Consolidated net income	(379)	0	0
Other income	$ (611)	$ 0	$ 0

Quarterly Financial Informati86

Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Apr. 02, 2016	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 523,524	$ 550,363	$ 614,266	$ 577,920	$ 472,158	$ 506,584	$ 544,071	$ 532,809
Gross profit	66,907	79,101	89,955	89,493	76,029	81,916	88,011	86,167
Consolidated net income	5,969	22,754	27,833	30,455	16,768	26,062	28,259	28,665	$ 87,011	$ 99,754	$ 88,407
Net income attributable to Mueller Industries, Inc.	$ 5,720	$ 22,258	$ 27,633	$ 29,987	$ 17,322	$ 25,978	$ 27,797	$ 28,630	$ 85,598	$ 99,727	$ 87,864
Basic earnings per share (in dollars per share)	$ 0.10	$ 0.39	$ 0.49	$ 0.53	$ 0.31	$ 0.46	$ 0.49	$ 0.51	$ 1.50	$ 1.76	$ 1.56
Diluted earnings per share (in dollars per share)	0.10	0.39	0.48	0.52	0.30	0.45	0.49	0.50	1.49	1.74	1.54
Dividends per share (in dollars per share)	$ 0.10	$ 0.10	$ 0.10	$ 8.1	$ 0.10	$ 0.10	$ 0.10	$ 0.075	$ 8.4	$ 0.375	$ 0.300
Impairment charges	$ 1,100				$ 3,800	$ 3,000			$ 1,466	$ 6,778	$ 0
Interest expense	4,300
Environmental expense, non operating properties	$ 6,200								$ 4,300	$ 800

SCHEDULE II-VALUATION AND QUA87

SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 637	$ 623	$ 666
Charged to costs and expenses	422	160	(130)
Other additions	(61)	2	201
Deductions	18	148	114
Balance at end of year	980	637	623
Balance of valuation allowance	637	623	666
Environmental Reserves [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	21,864	21,667	22,661
Charged to costs and expenses	7,491	894	76
Other additions	0	0	0
Deductions	1,351	697	1,070
Balance at end of year	28,004	21,864	21,667
Balance of valuation allowance	21,864	21,667	22,661
Valuation Allowance of Deferred Tax Assets [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	18,681	17,650	17,119
Charged to costs and expenses	7	3	(5)
Other additions	11,628	1,028	536
Deductions	0	0	0
Balance at end of year	30,316	18,681	17,650
Period increase in valuation allowance	11,600
Balance of valuation allowance	$ 18,681	$ 17,650	$ 17,119