SIGNIFICANT ACCOUNTING POLICIES - INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
SIGNIFICANT ACCOUNTING POLICIES
Tax Act, income tax expense (benefit)		$ 3.3
Remeasurement and discrete adjustments related to the Tax Act	$ (2.9)
Sequestration rate (as a percent)		6.20%

Amount of reasonable estimate for income tax expense (benefit) for remeasurement of deferred tax from change in tax rate pursuant to Tax Cuts and Jobs Act of 2017 for which accounting for tax effect is incomplete.

No definition available.

Name:	matx_TaxCutsAndJobsActOf2017IncompleteAccountingChangeInTaxRateProvisionalIncomeTaxExpenseBenefit
Namespace Prefix:	matx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration