Class Of Warrant Or Right Aggregate Purchase Price

No definition available.

Name:	mtga_ClassOfWarrantOrRightAggregatePurchasePrice
Namespace Prefix:	mtga_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Class Of Warrant Or Right Exercisable Period

+ References

No definition available.

+ Details

Name:	mtga_ClassOfWarrantOrRightExercisablePeriod
Namespace Prefix:	mtga_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Class Of Warrant Or Right Fully Diluted Share Capital Percentage

+ References

No definition available.

+ Details

Name:	mtga_ClassOfWarrantOrRightFullyDilutedShareCapitalPercentage
Namespace Prefix:	mtga_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Fixed Charge, Percentage

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentFixedChargePercentage
Namespace Prefix:	mtga_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument Interest Reserve Period

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentInterestReservePeriod
Namespace Prefix:	mtga_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Number Of Tranches

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentNumberOfTranches
Namespace Prefix:	mtga_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Period After First Draw For Prepayment

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentPeriodAfterFirstDrawForPrepayment
Namespace Prefix:	mtga_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line Of Credit Facility Credit Enhancement Support Amount

+ References

No definition available.

+ Details

Name:	mtga_LineOfCreditFacilityCreditEnhancementSupportAmount
Namespace Prefix:	mtga_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=123467817&loc=d3e21475-112644

+ Details

Name:	us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ References

+ Details

Name:	us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- 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

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

- Definition

Amount, after accumulated amortization, of debt discount.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28541-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1D
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
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=120391452&loc=d3e13212-122682

+ Details

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

- Definition

The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

+ 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 (e)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3291-108585

+ Details

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

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3255-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

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

- Definition

Value of outstanding derivative securities that permit the holder the right to purchase securities (usually equity) from the issuer at a specified price.

+ References

No definition available.

+ Details

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

- Definition

Value of input used to measure outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

Name:	us-gaap_WarrantsAndRightsOutstandingMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=mtga_WarrantsAndPutOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputDiscountRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=us-gaap_ValuationTechniqueDiscountedCashFlowMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputPriceVolatilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OptionIndexedToIssuersEquityTypeAxis=us-gaap_PutOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OptionIndexedToIssuersEquityTypeAxis=us-gaap_CallOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

Long-Term Debt - Narrative (Details) $ / shares in Units, $ in Thousands, ₩ in Millions			3 Months Ended
	Nov. 04, 2021 USD ($) $ / shares shares	Sep. 24, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2021 KRW (₩)	Sep. 24, 2021 KRW (₩) tranche
Short-term Debt [Line Items]
Debt issuance costs incurred			$ 65,050	$ 118
Proceeds from line of credit			341,075	$ 156,287
Inspire Korea Credit Facility
Short-term Debt [Line Items]
Borrowing capacity					$ 878,500	₩ 1,040,000.0	₩ 1,040,000.0
Number of tranches \| tranche							2
Debt instrument, term		48 months
Period after first draw for prepayment		1 year
Undrawn commitment fee percentage		0.30%
Credit enhancement support		$ 100,000
Debt issuance costs incurred		$ 59,000
MGE Korea Term Loan
Short-term Debt [Line Items]
Debt instrument, term	66 months
Stated interest rate	17.00%
Debt issuance costs incurred	$ 9,400
Proceeds from line of credit	$ 275,000
Fixed charge percentage from share capital and debenture	100.00%
Debt discount	$ 84,800
MGE Korea Warrants And Put Option Liability
Short-term Debt [Line Items]
Debt issuance costs incurred	$ 4,200
Number of warrants (in shares) \| shares	4,400
Initial warrant exercise price (in dollars per share) \| $ / shares	$ 0.01
Warrants, fully-diluted share capital percentage	22.00%
Aggregate purchase price	$ 110,000
MGE Korea Warrants And Put Option Liability \| Warrants And Put Option
Short-term Debt [Line Items]
Estimated fair value			$ 84,800
MGE Korea Warrants And Put Option Liability \| Warrants And Put Option \| Measurement Input, Discount Rate \| Valuation Technique, Discounted Cash Flow
Short-term Debt [Line Items]
Warrants, unobservable inputs			0.110
MGE Korea Warrants And Put Option Liability \| Warrants And Put Option \| Measurement Input, Price Volatility \| Valuation Technique, Discounted Cash Flow
Short-term Debt [Line Items]
Warrants, unobservable inputs			0.500
MGE Korea Warrants And Put Option Liability \| Put Option
Short-term Debt [Line Items]
Warrants exercisable period	6 years
MGE Korea Warrants And Put Option Liability \| Call Option
Short-term Debt [Line Items]
Warrants exercisable period	6 months
Tranche A Credit Facility \| Inspire Korea Credit Facility
Short-term Debt [Line Items]
Borrowing capacity					625,100	740,000.0	₩ 740,000.0
Stated interest rate							5.40%
Tranche B Credit Facility \| Inspire Korea Credit Facility
Short-term Debt [Line Items]
Borrowing capacity					$ 253,400	₩ 300,000.0	₩ 300,000.0
Stated interest rate							7.00%
Loan interest reserve period		36 months