Income Taxes: (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2012
Income Taxes:
Non-deductible separation costs	$ 1.7

The portion of the difference between total income tax expense (benefit) as reported in the income statement for the period and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to nondeductible separation costs under enacted tax laws.

No definition available.

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