Debt instrument maturity.

No definition available.

Name:	mgm_DebtInstrumentMaturity
Namespace Prefix:	mgm_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument maturity year.

+ References

No definition available.

+ Details

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Namespace Prefix:	mgm_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- 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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Data Type:	num:percentItemType
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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
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+ Details

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

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details

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

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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-Paragraph 6
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ 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

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

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

- Definition

Average fixed interest rate related to the group of interest rate derivatives.

+ References

No definition available.

+ Details

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

- 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
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-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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+ Details

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

- Definition

Maximum amount borrowed under the credit facility at any time during the period.

+ References

No definition available.

+ Details

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

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

+ Details

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

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

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

- Definition

The cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period.

+ References

+ Details

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

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mgm_SeniorSecuredTermLoanBMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mgm_TermLoanBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_CashFlowHedgingMember
Namespace Prefix:
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- Details

Name:	us-gaap_DebtInstrumentAxis=mgm_OperatingPartnershipSeniorNotesFivePointSevenFivePercentDueInTwoThousandTwentySevenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=mgm_BridgeFacilityMember
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

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Namespace Prefix:
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Namespace Prefix:
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Balance Type:
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- Details

Name:	us-gaap_LineOfCreditFacilityAxis=mgm_SeniorCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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Balance Type:
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Long-Term Debt - Additional Information (Detail) - USD ($)	1 Months Ended					8 Months Ended	9 Months Ended		12 Months Ended
	Aug. 31, 2019	May 31, 2019	Apr. 30, 2019	Feb. 28, 2019	Jan. 31, 2019	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Debt Instrument [Line Items]
Current portion of long-term debt, net of debt issuance costs						$ 0	$ 0		$ 43,411,000
Credit facility amount						15,066,825,000	15,066,825,000		15,253,239,000
Long-term debt, Gross						15,066,825,000	15,066,825,000		15,253,239,000
Repayments of senior notes							1,759,978,000	$ 2,265,000
Long-term debt, fair value						16,000,000,000	16,000,000,000		15,100,000,000
Term Loan A [Member] \| Operating Partnership Senior Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility amount						$ 467,000,000	$ 467,000,000
Debt instrument, interest rate						4.04%	4.04%
Long-term debt, Gross						$ 467,000,000	$ 467,000,000
Term Loan B [Member] \| Operating Partnership Senior Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility amount						$ 1,790,000,000	$ 1,790,000,000
Debt instrument, interest rate						4.04%	4.04%
Long-term debt, Gross						$ 1,790,000,000	$ 1,790,000,000
Term Loan B [Member] \| Interest Rate Swap [Member] \| Cash Flow Hedges [Member]
Debt Instrument [Line Items]
Notional amount						$ 1,500,000,000	$ 1,500,000,000
Weighted Average fixed interest rate						1.707%	1.707%
5.75% Operating Partnership senior notes, due 2027 [Member]
Debt Instrument [Line Items]
Long-term debt, principal amount					$ 750,000,000	$ 750,000,000	$ 750,000,000
Long-term debt, interest rate (as a percent)					5.75%	5.75%	5.75%
Long-term debt, maturity year					2027		2027
5.75% Operating Partnership senior notes, due 2027 [Member] \| Bridge Facility [Member] \| Empire City [Member]
Debt Instrument [Line Items]
Long-term debt, principal amount						$ 246,000,000	$ 246,000,000
Long-term debt, interest rate (as a percent)						5.75%	5.75%
Long-term debt, maturity year							2027
Senior Notes 5.50%, Due in 2027 [Member]
Debt Instrument [Line Items]
Long-term debt, principal amount			$ 1,000,000,000.0
Long-term debt, interest rate (as a percent)			5.50%
Long-term debt, maturity year			2027
6.75% senior notes, due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt, principal amount						$ 1,000,000,000	$ 1,000,000,000		$ 1,000,000,000
Long-term debt, interest rate (as a percent)			6.75%			6.75%	6.75%		6.75%
Long-term debt, maturity year			2020				2020		2020
Long-term debt, aggregate principal amount of debt purchased			$ 639,000,000
5.25% senior notes, due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt, principal amount						$ 500,000,000	$ 500,000,000		$ 500,000,000
Long-term debt, interest rate (as a percent)			5.25%			5.25%	5.25%		5.25%
Long-term debt, maturity year			2020				2020		2020
Long-term debt, aggregate principal amount of debt purchased			$ 233,000,000
8.625% senior notes, due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt, principal amount									$ 850,000,000
Long-term debt, interest rate (as a percent)				8.625%					8.625%
Long-term debt, maturity year				2019					2019
Repayments of senior notes				$ 850,000,000
5.375% MGM China senior notes, due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt, principal amount		$ 750,000,000				$ 750,000,000	$ 750,000,000
Long-term debt, interest rate (as a percent)		5.375%				5.375%	5.375%
Long-term debt, maturity year		2024					2024
5.875% MGM China senior notes, due 2026 [Member]
Debt Instrument [Line Items]
Long-term debt, principal amount		$ 750,000,000				$ 750,000,000	$ 750,000,000
Long-term debt, interest rate (as a percent)		5.875%				5.875%	5.875%
Long-term debt, maturity year		2026					2026
Senior Credit Facility [Member] \| Term Loan A [Member]
Debt Instrument [Line Items]
Credit facility amount						$ 750,000,000	$ 750,000,000
Debt instrument, interest rate						4.04%	4.04%
Long-term debt, Gross						$ 750,000,000	$ 750,000,000
MGM China Credit Facility [Member]
Debt Instrument [Line Items]
Current portion of long-term debt, net of debt issuance costs									$ 43,000,000
Credit facility amount						775,658,000	775,658,000		2,433,562,000
Long-term debt, Gross						775,658,000	775,658,000		$ 2,433,562,000
Revolving Credit Facility [Member] \| Operating Partnership Senior Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility						1,350,000,000	1,350,000,000
Line of credit facility drawn						0	0
Revolving Credit Facility [Member] \| MGM China Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, maturity date	2024-05
Revolving Credit Facility [Member] \| MGM China Credit Facility [Member] \| Hong Kong Interbank Offered Rate HIBOR [Member]
Debt Instrument [Line Items]
Variable interest rate base	HIBOR
Revolving Credit Facility [Member] \| MGM China Credit Facility [Member] \| Minimum [Member] \| Hong Kong Interbank Offered Rate HIBOR [Member]
Debt Instrument [Line Items]
Interest rate margin (as a percent)	1.625%
Revolving Credit Facility [Member] \| MGM China Credit Facility [Member] \| Maximum [Member] \| Hong Kong Interbank Offered Rate HIBOR [Member]
Debt Instrument [Line Items]
Interest rate margin (as a percent)	2.75%
Revolving Credit Facility [Member] \| Senior Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility						1,500,000,000	1,500,000,000
Line of credit facility drawn						$ 510,000,000	$ 510,000,000
Debt instrument, interest rate						4.03%	4.03%
Unsecured Revolving Credit Facility [Member] \| MGM China Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility						$ 1,250,000,000	$ 1,250,000,000
Credit facility amount	$ 1,250,000,000
Line of credit facility drawn	776,000,000
Long-term debt, Gross	$ 1,250,000,000
Term Loan [Member] \| MGM China Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate						4.25%	4.25%
Repayments of previous term loan							$ 1,000,000,000.0
Revolving credit facility outstanding						$ 776,000,000