XML 88 R70.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Benefit Plans - Contributions and Benefit Payments, Multiemployer Plan, 401(k) Plans and UMWA Benefit Plans (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 30, 2017 USD ($) bargain_agreement | Dec. 31, 2016 USD ($) | Dec. 26, 2015 USD ($)
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 |  |

X
- Definition Amount of contributions to the United Mine Workers of America 1992 Benefit Plan. + References No definition available. + Details
Name: | mli_CoalIndustryRetireeHealthBenefitActOf1992PlanContributions
Namespace Prefix: | mli_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | mli_IamPlanTrustsAbstract
Namespace Prefix: | mli_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | mli_KPlanAbstract
Namespace Prefix: | mli_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The maximum percentage of employer contributions related to a defined pension plan or trust during the period. + References No definition available. + Details
Name: | mli_MaximumPercentageOfEmployerContributions
Namespace Prefix: | mli_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of collective bargaining agreements related to negotiation on participation on defined benefit plan. + References No definition available. + Details
Name: | mli_NumberOfCollectiveBargainingAgreements
Namespace Prefix: | mli_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of the cost recognized during the period for defined contribution plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
Name: | us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of contributions made to multiemployer plans by the employer. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450702-114947 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450691-114947 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 5 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947 + Details
Name: | us-gaap_MultiemployerPlanPeriodContributions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |