Represents information pertaining to early retirement age under the benefit plan.

No definition available.

Name:	mic_DefinedBenefitPlanEarlyRetirementAge
Namespace Prefix:	mic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Benefit Plan Retirement Age Minimum.

+ References

No definition available.

+ Details

Name:	mic_DefinedBenefitPlanRetirementAgeMinimum
Namespace Prefix:	mic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents information pertaining to consecutive period based on years of service and the employees' highest average compensation during the reporting period.

+ References

No definition available.

+ Details

Name:	mic_DefinedContributionPlanConsecutivePeriodBasedOnYearsOfServiceAndEmployeesHighestAverageCompensation
Namespace Prefix:	mic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of match contributions made by an employer to a defined contribution plan.

+ References

No definition available.

+ Details

Name:	mic_DefinedContributionPlanEmployerMatchingContribution
Namespace Prefix:	mic_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents information pertaining to maximum compensation amount in final year under the benefit plan.

+ References

No definition available.

+ Details

Name:	mic_DefinedContributionPlanFinalYearCompensationMaximumAmount
Namespace Prefix:	mic_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents information pertaining to final year compensation in term of percentage under the benefit plan.

+ References

No definition available.

+ Details

Name:	mic_DefinedContributionPlanFinalYearCompensationPercentage
Namespace Prefix:	mic_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents information pertaining to minimum service period for eligible to participate in defined benefit plan during the reporting period.

+ References

No definition available.

+ Details

Name:	mic_DefinedContributionPlanMinimumServicePeriodForEligibleToParticipate
Namespace Prefix:	mic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Life Insurance Contracts Death Benefits To Insured

+ References

No definition available.

+ Details

Name:	mic_LifeinsuranceContractsDeathBenefitsToInsured
Namespace Prefix:	mic_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The maximum age for which business pays medical premium of the retirees and spouses.

+ References

No definition available.

+ Details

Name:	mic_MaximumAgeForWhichBusinessPaysMedicalPremiumOfTheRetireesAndSpouses
Namespace Prefix:	mic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Medical Premiums Payment

+ References

No definition available.

+ Details

Name:	mic_MedicalPremiumsPayment
Namespace Prefix:	mic_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mic_InternationalMatexTankTerminalsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=mic_BayonneTerminalEmployeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mic_MicHawaiiMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsegmentsAxis=mic_HawaiiGasBusinessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_DefinedBenefitPostretirementLifeInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Employee Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
Employee Benefit Plans (Narrative) (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Contribution Plan Disclosure [Line Items]
Employer contributions - defined contribution plan	$ 5,000,000	$ 5,000,000	$ 4,000,000
IMTT \| DB Plans Benefits
Defined Contribution Plan Disclosure [Line Items]
Consecutive period based on years of service and the employees' highest average compensation	5 years
Final year compensation (as a percentage)	25.00%
Maximum compensation amount in final year	$ 25,000
Early retirement age	62 years
IMTT \| DB Plans Benefits \| Bayonne Terminal Employees
Defined Contribution Plan Disclosure [Line Items]
Minimum required retirement age - defined benefit plan	65 years
MIC Hawaii \| DB Plans Benefits
Defined Contribution Plan Disclosure [Line Items]
Employer contributions - defined contribution plan		$ 0
Minimum
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent of employees' gross pay	0.00%
Maximum
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent of employees' gross pay	7.00%
Hawaii Gas Business \| MIC Hawaii \| DB Plans Benefits
Defined Contribution Plan Disclosure [Line Items]
Employer contributions - defined contribution plan	$ 0
Hawaii Gas Business \| MIC Hawaii \| PMLI Benefits
Defined Contribution Plan Disclosure [Line Items]
Minimum required retirement age - defined benefit plan	62 years
Minimum service period to eligible for participate	15 years
Maximum age for which business pays medical premium of the retirees and spouses	64 years
Maximum monthly premium after attaining age of 65 years	$ 150
Life insurance benefits for retirees - defined benefit plan	$ 1,000