Minority interest ownership percentage in consolidated subsidiary.

No definition available.

Name:	mgm_MinorityInterestOwnershipPercentageInConsolidatedSubsidiary
Namespace Prefix:	mgm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Minority interest ownership percentage in unconsolidated affiliate.

+ References

No definition available.

+ Details

Name:	mgm_MinorityInterestOwnershipPercentageInUnconsolidatedAffiliate
Namespace Prefix:	mgm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of integrated casino.

+ References

No definition available.

+ Details

Name:	mgm_NumberOfIntegratedCasino
Namespace Prefix:	mgm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Organization disclosure.

+ References

No definition available.

+ Details

Name:	mgm_OrganizationDisclosureLineItems
Namespace Prefix:	mgm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percent interest in a less than hundred percent owned consolidated affiliate.

+ References

No definition available.

+ Details

Name:	mgm_PercentInterestInALessThanHundredPercentOwnedConsolidatedAffiliate
Namespace Prefix:	mgm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Required minimum ownership percentage in beneficial ownership to entitle majority of voting power.

+ References

No definition available.

+ Details

Name:	mgm_RequiredMinimumOwnershipPercentageInBeneficialOwnershipToEntitleMajorityOfVotingPower
Namespace Prefix:	mgm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of voting rights of common stock. Includes eligibility to vote and votes per share owned. Include also, if any, unusual voting rights.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

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

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

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

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of subsidiary's or equity investee's stock owned by parent company after stock transaction.

+ References

No definition available.

+ Details

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

- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 5A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121559654&loc=SL6759159-111685

+ Details

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

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=mgm_CityCenterHoldingsLLCAsInvesteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=mgm_BetMGMLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OtherOwnershipInterestsByNameAxis=mgm_InfinityWorldDevelopmentCorpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OtherOwnershipInterestsByNameAxis=mgm_EntainPLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mgm_BellagioBREITVentureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mgm_MGPBREITVentureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=mgm_SubsidiaryOfBlackstoneRealEstateIncomeTrustMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=mgm_MGMChinaHoldingsLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CapitalUnitsByClassAxis=us-gaap_CapitalUnitClassAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=mgm_NonGuarantorMGPSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CapitalUnitsByClassAxis=us-gaap_CapitalUnitClassBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=mgm_MGMGrowthPropertiesLimitedLiabilityCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Organization - Additional Information (Detail)	3 Months Ended
Organization - Additional Information (Detail)	Mar. 31, 2021 Property Segment	Dec. 31, 2020
Organization Disclosure [Line Items]
Number of reportable segments \| Segment	3
CityCenter Holdings LLC As Investee [Member]
Organization Disclosure [Line Items]
Percentage ownership interest	50.00%	50.00%
BetMGM LLC [Member]
Organization Disclosure [Line Items]
Percentage ownership interest	50.00%	50.00%
Infinity World Development Corp [Member] \| CityCenter Holdings LLC As Investee [Member]
Organization Disclosure [Line Items]
Percentage ownership interest	50.00%
Entain plc [Member] \| BetMGM LLC [Member]
Organization Disclosure [Line Items]
Percentage ownership interest	50.00%
Bellagio BREIT Venture [Member]
Organization Disclosure [Line Items]
Percentage of minority interest	5.00%
MGP BREIT Venture [Member]
Organization Disclosure [Line Items]
Partnership interest	50.10%
Percentage of minority interest	49.90%
Subsidiary of Blackstone Real Estate Income Trust [Member] \| Bellagio BREIT Venture [Member]
Organization Disclosure [Line Items]
Percentage of ownership interest	95.00%
MGM China [Member]
Organization Disclosure [Line Items]
Percentage ownership interest	56.00%
Number of integrated casino \| Property	2
Class A shares [Member]
Organization Disclosure [Line Items]
Common stock voting rights	one vote per share
Non-Guarantor MGP Subsidiaries [Member] \| Class B shares [Member]
Organization Disclosure [Line Items]
Common stock voting rights	Class B share, is entitled to an amount of votes representing a majority of the total voting power of MGP’s shares so long as the Company and its controlled affiliates’ (excluding MGP) aggregate beneficial ownership of the combined economic interests in MGP and the Operating Partnership does not fall below 30%.
MGM Growth Properties LLC [Member]
Organization Disclosure [Line Items]
Minimum ownership percentage required for majority voting interest	30.00%
Partnership interest	42.10%
Percentage of minority interest	57.90%