Expected funding deficiency period for determining zone status.

No definition available.

Name:	matx_MultiEmployerPlanExpectedFundingDeficiencyPeriod
Namespace Prefix:	matx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the funded status of a multiemployer plan.

+ References

No definition available.

+ Details

Name:	matx_MultiemployerPlanFundedPercentage
Namespace Prefix:	matx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of contributions made to multiemployer plan by employer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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_MultiemployerPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of accumulated benefit obligation attributable to the 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 7
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450678-114947

+ Details

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

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

PENSION AND POST-RETIREMENT PLANS - MULTI-EMPLOYER DEFINED BENEFIT PLANS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Multiemployer Plans
Multiemployer Plans, Accumulated Benefit Obligation	$ 266.7
Multiemployer Benefit Pension Plans
Multiemployer Plans
Contributions of Matson	$ 27.3	$ 25.5	$ 24.4
Multiemployer Benefit Pension Plans \| Orange Zone
Multiemployer Plans
Expected funding deficiency period	6 years
Multiemployer Benefit Pension Plans \| Minimum \| Green Zone
Multiemployer Plans
Funded status of multiemployer plan (as a percent)	80.00%
Multiemployer Benefit Pension Plans \| Maximum \| Red Zone
Multiemployer Plans
Funded status of multiemployer plan (as a percent)	65.00%
Multiemployer Benefit Pension Plans \| Maximum \| Yellow Zone
Multiemployer Plans
Funded status of multiemployer plan (as a percent)	80.00%
Multiemployer Benefit Pension Plans \| Maximum \| Orange Zone
Multiemployer Plans
Funded status of multiemployer plan (as a percent)	80.00%
Multiemployer Benefit Pension Plans \| American Radio Association Pension Fund \| Green Zone
Multiemployer Plans
Contributions of Matson	$ 1.1	1.0	1.0
Multiemployer Benefit Pension Plans \| Hawaii Terminals Multiemployer Pension Plan \| Orange Zone
Multiemployer Plans
Contributions of Matson	5.7	5.7	5.7
Multiemployer Benefit Pension Plans \| Hawaii Stevedoring Multiemployer Retirement Plan \| Yellow Zone
Multiemployer Plans
Contributions of Matson	4.4	4.3	3.8
Multiemployer Benefit Pension Plans \| Master Mates And Pilots Pension Plan \| Green Zone
Multiemployer Plans
Contributions of Matson	3.4	3.0	3.0
Multiemployer Benefit Pension Plans \| Masters, Mates and Pilots Adjustable Pension Plan
Multiemployer Plans
Contributions of Matson	1.9	1.7	1.7
Multiemployer Benefit Pension Plans \| O C U Trust Pension Plan \| Green Zone
Multiemployer Plans
Contributions of Matson	0.2	0.2	0.2
Multiemployer Benefit Pension Plans \| M F O W Supplementary Pension Plan \| Green Zone
Multiemployer Plans
Contributions of Matson	0.1
Multiemployer Benefit Pension Plans \| SIU Pacific District Pension Plan \| Green Zone
Multiemployer Plans
Contributions of Matson	1.5	1.2	0.7
Multiemployer Benefit Pension Plans \| Alaska Teamster - Employer Pension Plan \| Red Zone
Multiemployer Plans
Contributions of Matson	1.9	1.9	2.4
Multiemployer Benefit Pension Plans \| All Alaska Longshore Pension Plan \| Green Zone
Multiemployer Plans
Contributions of Matson	1.2	1.0	0.1
Multiemployer Benefit Pension Plans \| Western Conference of Teamsters Pension Plan \| Green Zone
Multiemployer Plans
Contributions of Matson	1.5	1.4	1.3
Multiemployer Benefit Pension Plans \| O P E I U Local 153 Pension Plan \| Red Zone
Multiemployer Plans
Contributions of Matson	0.1	0.1	0.1
Multiemployer Benefit Postretirement Plans
Multiemployer Plans
Contributions of Matson	32.8	30.0	27.0
Multi-employer defined contribution pension plans \| M E B A Pension Trust - Defined Benefit Plan \| Green Zone
Multiemployer Plans
Contributions of Matson	$ 4.3	$ 4.0	$ 4.4