The percentage of the variable rate to determine the interest rate on the debt instrument.

No definition available.

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Namespace Prefix:	mic_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Increased amount of unhedged debt.

+ References

No definition available.

+ Details

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Namespace Prefix:	mic_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of total debt outstanding at the balance sheet date that is not hedged with a derivative instrument.

+ References

No definition available.

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the aggregate of total long-term debt, including current maturities and short-term debt.

+ References

No definition available.

+ Details

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

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of hedged item in hedging relationship. Excludes hedged asset or liability.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Cap rate on an interest rate derivative such as an interest rate cap or collar. If market rates exceed the cap rate, a payment or receipt is triggered on the contract.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeCapInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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

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

- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	duration

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
Namespace Prefix:
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Balance Type:
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- Details

Name:	us-gaap_CreditFacilityAxis=mic_TaxExemptBondsMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mic_InternationalMatexTankTerminalsMember
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Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=mic_TermLoanFacilityMember
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Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mic_AtlanticAviationMember
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- Details

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Derivative Instruments and Hedging Activities (Narrative) (Details) gal in Millions				1 Months Ended		12 Months Ended
	Dec. 06, 2018 USD ($)	Dec. 05, 2018 USD ($)	Jun. 01, 2015 USD ($)	Jul. 31, 2016 USD ($)	May 31, 2015 USD ($)	Dec. 31, 2019 USD ($) gal	Dec. 31, 2018 USD ($)	Oct. 31, 2016 USD ($)	Feb. 29, 2016 USD ($)	Feb. 10, 2016 USD ($)
Derivative [Line Items]
Long-term and short-term debt						$ 2,722,000,000	$ 3,083,000,000
Fixed rate debt						1,103,000,000	1,453,000,000
Unhedged debt						673,000,000	683,000,000
Interest Rate Contracts
Derivative [Line Items]
Debt economically hedged with interest rate contracts						$ 946,000,000	$ 947,000,000
Tax Exempt Bonds \| IMTT
Derivative [Line Items]
Percentage of the variable rate		80.00%				80.00%
Fixed portion of interest rate component		0.45%				0.45%
Increase in unhedged debt		$ 58,000,000
Borrowing capacity		$ 509,000,000
Tax Exempt Bonds \| IMTT \| Interest Rate Swap
Derivative [Line Items]
Notional amount of derivative			$ 361,000,000		$ 361,000,000
Derivative, term of contract			6 years		6 years
Fixed interest rate			1.677%		1.677%
Term Loan Facility \| Atlantic Aviation
Derivative [Line Items]
Borrowing capacity	$ 1,025,000,000					$ 1,025,000,000.0
Debt instrument, term	7 years
Term Loan Facility \| Atlantic Aviation \| Interest Rate Cap
Derivative [Line Items]
Notional amount of derivative								$ 400,000,000
Derivative, cap interest rate								1.00%
Hawaii Gas Business \| MIC Hawaii \| Commodity Price Hedges
Derivative [Line Items]
Nonmonetary notional amount, volume \| gal						38
Hawaii Gas Business \| Term Loan Facility \| MIC Hawaii
Derivative [Line Items]
Borrowing capacity						$ 80,000,000				$ 80,000,000
Hawaii Gas Business \| Term Loan Facility \| MIC Hawaii \| Interest Rate Swap
Derivative [Line Items]
Notional amount of derivative									$ 80,000,000
Fixed interest rate						0.99%
Weighted average interest rate						2.49%
Solar Power Facilities \| Term Loan Facility \| MIC Hawaii
Derivative [Line Items]
Fixed portion of interest rate component				2.00%
Borrowing capacity				$ 18,000,000
Debt instrument, term				10 years
Solar Power Facilities \| Term Loan Facility \| MIC Hawaii \| Interest Rate Swap
Derivative [Line Items]
Notional amount of derivative				$ 18,000,000
Weighted average interest rate						3.38%