Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings

No definition available.

Name:	mli_TaxCutsandJobsActof2017ReclassificationfromAOCItoRetainedEarnings
Namespace Prefix:	mli_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_AOCIAttributableToParentNetOfTaxRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount after tax, before reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=109228884&loc=d3e1436-108581

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount after tax and reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669619-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=109228884&loc=d3e1436-108581

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669625-108580

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount after tax of reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 17B
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL34724394-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=109228884&loc=d3e1436-108581

+ Details

Name:	us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4568740-111683

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 55
-Paragraph 4I
-URI http://asc.fasb.org/extlink&oid=84234705&loc=SL4590271-111686

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4568447-111683

+ Details

Name:	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedOtherComprehensiveIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedTranslationAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=mli_AccumulatedOtherComprehensiveIncomeAttributabletoUnconsolidatedAffiliatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Accumulated Other Comprehensive Income (Loss) - Changes by Component (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 29, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Changes in accumulated other comprehensive income [Roll Forward]
Beginning balance		$ 536,028		$ 536,028
Total other comprehensive (loss) income, net	$ (5,395)		$ 6,080	(12,848)	$ 13,417
Reclassification of stranded effects of the Act		556
Ending balance	583,408			583,408
Total [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Beginning balance		(51,056)		(51,056)	(66,956)
Other comprehensive (loss) income before reclassifications				(12,220)	14,638
Amounts reclassified from AOCI				(237)	(2,059)
Total other comprehensive (loss) income, net				(12,457)	12,579
Reclassification of stranded effects of the Act				556
Ending balance	(62,957)		(54,377)	(62,957)	(54,377)
Cumulative Translation Adjustment [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Beginning balance		(38,163)		(38,163)	(49,965)
Other comprehensive (loss) income before reclassifications				(5,143)	18,209
Amounts reclassified from AOCI				0	(3,777)
Total other comprehensive (loss) income, net				(5,143)	14,432
Reclassification of stranded effects of the Act				0
Ending balance	(43,306)		(35,533)	(43,306)	(35,533)
Unrealized (Loss) Gain on Derivatives [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Beginning balance		847		847	(300)
Other comprehensive (loss) income before reclassifications				(441)	(1,175)
Amounts reclassified from AOCI				(455)	1,360
Total other comprehensive (loss) income, net				(896)	185
Reclassification of stranded effects of the Act				112
Ending balance	63		(115)	63	(115)
Pension/OPEB Liability Adjustment [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Beginning balance		(20,610)		(20,610)	(23,046)
Other comprehensive (loss) income before reclassifications				551	(1,309)
Amounts reclassified from AOCI				218	737
Total other comprehensive (loss) income, net				769	(572)
Reclassification of stranded effects of the Act				(1,018)
Ending balance	(20,859)		(23,618)	(20,859)	(23,618)
Unrealized Gain (Loss) on Equity Securities [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Beginning balance		0		0	380
Other comprehensive (loss) income before reclassifications				0	(1)
Amounts reclassified from AOCI				0	(379)
Total other comprehensive (loss) income, net				0	(380)
Reclassification of stranded effects of the Act				0
Ending balance	0		0	0	0
Attributable to Unconsolidated Affiliates [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Beginning balance		$ 6,870		6,870	5,975
Other comprehensive (loss) income before reclassifications				(7,187)	(1,086)
Amounts reclassified from AOCI				0	0
Total other comprehensive (loss) income, net				(7,187)	(1,086)
Reclassification of stranded effects of the Act				1,462
Ending balance	$ 1,145		$ 4,889	$ 1,145	$ 4,889