Name:	alex_DefinedContributionPlanContributionPercentageMaximum
Namespace Prefix:	alex_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The minimum percentage of contributions to the plan, based on pre-defined criteria (e.g. eligible employee compensation or Company performance above minimum threshold).

No definition available.

Name:	alex_DefinedContributionPlanContributionPercentageMinimum
Namespace Prefix:	alex_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The EIN/Pension Plan Number for the disclosed pension fund in the multiemployer plan.

No definition available.

Name:	alex_MultiemployerPlanEinPensionPlanNumber
Namespace Prefix:	alex_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The Expiration Date of Collective Bargaining Agreement for the disclosed pension fund in the multiemployer plan.

No definition available.

Name:	alex_MultiemployerPlanExpirationDateOfCollectiveBargainingAgreement
Namespace Prefix:	alex_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

The earliest Expiration Date of Collective Bargaining Agreement for the disclosed pension fund in the multiemployer plan.

No definition available.

Name:	alex_MultiEmployerPlanExpirationDateOfCollectiveBargainingAgreementEarliest
Namespace Prefix:	alex_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

The latest Expiration Date of Collective Bargaining Agreement for the disclosed pension fund in the multiemployer plan.

No definition available.

Name:	alex_MultiEmployerPlanExpirationDateOfCollectiveBargainingAgreementLatest
Namespace Prefix:	alex_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

The FIP/RP Status (Pending or Implemented) for the disclosed pension fund in the multiemployer plan.

No definition available.

Name:	alex_MultiemployerPlanFipRpStatusPendingImplemented
Namespace Prefix:	alex_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The maximum funded percentage of multiemployer plans in the red zone.

No definition available.

Name:	alex_MultiemployerPlanMaximumFundedPercentageOfPlansInRedZone
Namespace Prefix:	alex_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The maximum funded percentage of multiemployer plans in the yellow zone.

No definition available.

Name:	alex_MultiemployerPlanMaximumFundedPercentageOfPlansInYellowZone
Namespace Prefix:	alex_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The minimum funded percentage of multiemployer plans in the green zone.

No definition available.

Name:	alex_MultiemployerPlanMinimumFundedPercentageOfPlansInGreenZone
Namespace Prefix:	alex_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The number of multiemployer plans.

No definition available.

Name:	alex_MultiemployerPlanNumberOfMultiemployerPlans
Namespace Prefix:	alex_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The Pension Protection Act Zone Status for the disclosed pension fund in the multiemployer plan.

No definition available.

Name:	alex_MultiemployerPlanPensionProtectionActZoneStatus
Namespace Prefix:	alex_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The Surcharge Imposed for the disclosed pension fund in the multiemployer plan.

No definition available.

Name:	alex_MultiemployerPlanSurchargeImposed
Namespace Prefix:	alex_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The threshold of total contributions for which multiemployer plans and years are disclosed.

No definition available.

Name:	alex_MultiemployerPlanThresholdOfTotalContributionsForWhichPlansAndYearsAreDisclosed
Namespace Prefix:	alex_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The number of collective-bargaining agreements based upon vessels that require contributions to the plan to which Mason is a party to.

No definition available.

Name:	alex_NumberOfCollectiveBargainingAgreementsBasedUponVesselsThatRequireContributionsToPlan
Namespace Prefix:	alex_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The number of vessels covered by Contract A relating to the collective-bargaining agreements.

No definition available.

Name:	alex_NumberOfVesselsCoveredByContractA
Namespace Prefix:	alex_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The number of vessels covered by Contract B relating to the collective-bargaining agreements.

No definition available.

Name:	alex_NumberOfVesselsCoveredByContractB
Namespace Prefix:	alex_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	alex_ScheduleOfMultiemployerPlansLineItems
Namespace Prefix:	alex_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The number of years amortization period provided by Public Law 111-192, Section 211 for the amortization of losses.

No definition available.

Name:	alex_SpecialAmortizationRulesProvidedByPublicLaw
Namespace Prefix:	alex_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

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

The amount of the cost recognized during the period for defined contribution plans.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 11

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: 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=6414718&loc=d3e28014-114942

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

General descriptive information regarding an employer's multiemployer plans. A multiemployer plan is a plan to which two or more unrelated employers contribute, usually pursuant to one or more collective-bargaining agreements. A characteristic of multiemployer plans is that assets contributed by one participating employer may be used to provide benefits to employees of other participating employers since assets contributed by one employer are not segregated in a separate account or restricted to provide benefits only to employees of that employer. A multiemployer plan is usually administered by a board of trustees composed of management and labor representatives and may also be referred to as a "joint trust" or "union" plan. Generally, many employers participate in a multiemployer plan, and an employer may participate in more than one plan. The employers participating in multiemployer plans usually have a common industry bond, but for some plans the employers are in different industries and the labor union may be their only common bond.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Section 50

-Paragraph 1

-SubTopic 80

-Topic 715

-URI http://asc.fasb.org/extlink&oid=6958064&loc=d3e29142-114947

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 87

-Paragraph 67

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Multiemployer Plan

-URI http://asc.fasb.org/extlink&oid=6517991

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

Amount of contributions made to multiemployer plans for each period for which a statement of income is presented. An employer may disclose total contributions to multiemployer plans without disaggregating the amounts attributable to pension plans and other postretirement benefit plans.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Section 50

-Paragraph 1

-SubTopic 80

-Topic 715

-URI http://asc.fasb.org/extlink&oid=6958064&loc=d3e29142-114947