Fair value of the amount outstanding under the credit facility.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13433-108611

+ Details

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

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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

- Details

Name:	us-gaap_DebtInstrumentAxis=mtga_InspireKoreaCreditFacilityMember
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 - Inspire Integrated Resort Credit Facility Summary (Details) - Inspire Korea Credit Facility ₩ in Millions, $ in Millions	Dec. 31, 2021 KRW (₩)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 KRW (₩)	Sep. 30, 2021 USD ($)	Sep. 24, 2021 KRW (₩)
Line of Credit Facility [Line Items]
Total Capacity			₩ 1,040,000.0	$ 878.5	₩ 1,040,000.0
Outstanding Borrowings (Face Value)	₩ 208,000.0	$ 175.0
Tranche A Credit Facility
Line of Credit Facility [Line Items]
Total Capacity			740,000.0	625.1	740,000.0
Outstanding Borrowings (Face Value)	148,000.0	124.5
Tranche B Credit Facility
Line of Credit Facility [Line Items]
Total Capacity			₩ 300,000.0	$ 253.4	₩ 300,000.0
Outstanding Borrowings (Face Value)	₩ 60,000.0	$ 50.5