Cash in exchange due to leasehold interest and real property.

No definition available.

Name:	mgm_CashInExchangeDueToLeaseholdInterestAndRealProperty
Namespace Prefix:	mgm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Issuance of operating partnership units.

+ References

No definition available.

+ Details

Name:	mgm_IssuanceOfOperatingPartnershipUnits
Namespace Prefix:	mgm_
Data Type:	xbrli:sharesItemType
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

Stockholders equity note.

+ References

No definition available.

+ Details

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

- Definition

Tender offer expiration date.

+ References

No definition available.

+ Details

Name:	mgm_TenderOfferExpirationDate
Namespace Prefix:	mgm_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Tender offer issued to repurchase shares period value.

+ References

No definition available.

+ Details

Name:	mgm_TenderOfferIssuedToRepurchaseSharesPeriodValue
Namespace Prefix:	mgm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: 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(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Date the declared dividend will be paid, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

+ Details

Name:	us-gaap_DividendPayableDateToBePaidDayMonthAndYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

+ Details

Name:	us-gaap_DividendsPayableAmountPerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Date the dividend to be paid was declared, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_DividendsPayableDateDeclaredDayMonthAndYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

Name:	us-gaap_DividendsPayableDateOfRecordDayMonthAndYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of new stock issued during the period.

+ 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(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: 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(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount remaining of a stock repurchase plan authorized.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of shares that have been repurchased and retired during the period.

+ 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(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 3: 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(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

+ Details

Name:	us-gaap_StockRepurchasedAndRetiredDuringPeriodShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital).

+ 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(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: 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(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

+ Details

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

- Definition

Total cost of shares repurchased divided by the total number of shares repurchased.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

+ Details

Name:	us-gaap_TreasuryStockAcquiredAverageCostPerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=mgm_ShareRepurchaseProgramOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=mgm_ShareRepurchaseProgramTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=mgm_ShareRepurchaseProgramThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=mgm_ShareRepurchaseProgramMember
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:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=mgm_NorthfieldOperatingCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=mgm_TermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_BusinessAcquisitionAxis=mgm_EmpireCityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=mgm_ParkMGMMember
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:	us-gaap_SubsidiarySaleOfStockAxis=mgm_UnderwritersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=mgm_ForwardPurchasersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands							1 Months Ended			12 Months Ended
	Feb. 13, 2020	Feb. 12, 2020	Jan. 01, 2020	Nov. 22, 2019	Oct. 15, 2017	Sep. 11, 2017	Apr. 30, 2019	Mar. 31, 2019	Jan. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 31, 2018	Sep. 30, 2017
Stockholders Equity Note [Line Items]
Long-term debt, Gross										$ 11,271,706,000	$ 15,253,239,000
Repurchase of common stock										$ 1,031,534,000	$ 1,283,333,000	$ 327,500,000
Subsequent Event [Member]
Stockholders Equity Note [Line Items]
Dividend declared date		Feb. 12, 2020
Dividends declared per share		$ 0.15
Dividends paid date		Mar. 16, 2020
Dividend record date		Mar. 10, 2020
Common Stock [Member]
Stockholders Equity Note [Line Items]
Common stock repurchases, Shares										35,854	41,076	10,000
Repurchase of common stock										$ 358,000	$ 411,000	$ 100,000
Share Repurchase Program [Member] \| Common Stock [Member]
Stockholders Equity Note [Line Items]
Authorized amount of stock repurchase										2,000,000,000.0			$ 2,000,000,000.0
Repurchase of common stock, remaining amount										$ 357,000,000
Share Repurchase Program Two [Member] \| Common Stock [Member]
Stockholders Equity Note [Line Items]
Authorized amount of stock repurchase														$ 1,000,000,000.0
Share Repurchase Program Three [Member] \| Common Stock [Member] \| Subsequent Event [Member]
Stockholders Equity Note [Line Items]
Authorized amount of stock repurchase		$ 3,000,000,000.0
Share Repurchase Program [Member]
Stockholders Equity Note [Line Items]
Tender offer expiration date										Mar. 12, 2020
Share Repurchase Program [Member] \| Common Stock [Member]
Stockholders Equity Note [Line Items]
Common stock repurchases, Shares										36,000	41,000
Stock repurchased, average price per share										$ 28.77	$ 31.25
Repurchase of common stock										$ 1,000,000,000.0	$ 1,300,000,000
Share Repurchase Program [Member] \| Common Stock [Member] \| Subsequent Event [Member]
Stockholders Equity Note [Line Items]
Common stock repurchases, Shares			11,000
Stock repurchased, average price per share			$ 32.57
Repurchase of common stock			$ 354,000,000
Tender offer	$ 1,250,000
Share Repurchase Program [Member] \| Common Stock [Member] \| Subsequent Event [Member] \| Maximum [Member]
Stockholders Equity Note [Line Items]
Stock repurchased, average price per share	$ 34
Share Repurchase Program [Member] \| Common Stock [Member] \| Subsequent Event [Member] \| Minimum [Member]
Stockholders Equity Note [Line Items]
Stock repurchased, average price per share	$ 29
Northfield OpCo [Member]
Stockholders Equity Note [Line Items]
Issuance of operating partnership units							9,000
MGM National Harbor Transaction [Member]
Stockholders Equity Note [Line Items]
Issuance of operating partnership units					9,800
Cash in exchange					$ 463,000,000
Term Loan [Member] \| MGM National Harbor Transaction [Member]
Stockholders Equity Note [Line Items]
Long-term debt, Gross					$ 425,000,000
MGM Growth Properties LLC [Member]
Stockholders Equity Note [Line Items]
Partnership interest					73.40%	72.30%	68.80%	69.80%	74.60%	63.70%
MGM Growth Properties LLC [Member] \| Empire City [Member]
Stockholders Equity Note [Line Items]
Issuance of operating partnership units									13,000
MGM Growth Properties LLC [Member] \| Park MGM [Member]
Stockholders Equity Note [Line Items]
Issuance of operating partnership units								1,000
Class A shares [Member] \| MGM Growth Properties LLC [Member]
Stockholders Equity Note [Line Items]
New issuance of shares				30,000		13,200			20,000	5,000
Issuance of operating partnership units				18,000		13,200			20,000	5,000
Partnership interest				63.70%					69.70%	63.70%
Class A shares [Member] \| MGM Growth Properties LLC [Member] \| Underwriters [Member]
Stockholders Equity Note [Line Items]
New issuance of shares				18,000
Class A shares [Member] \| MGM Growth Properties LLC [Member] \| Forward Purchasers [Member]
Stockholders Equity Note [Line Items]
New issuance of shares				12,000