ORGANIZATION AND BASIS OF PRESENTATION (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Senior Secured Credit Facility - Revolving \| Credit Facility \| Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	$ 66,000
Senior Secured Credit Facility - Revolving \| Credit Facility \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	60,803
Senior Secured Credit Facility - Term Loan A \| Credit Facility \| Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	295,424
Senior Secured Credit Facility - Term Loan A \| Credit Facility \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	281,846
Senior Secured Credit Facility - Term Loan B \| Credit Facility \| Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	809,160
Senior Secured Credit Facility - Term Loan B \| Credit Facility \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	$ 735,587
2016 7 7/8% Senior Unsecured Notes \| Senior Unsecured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note stated interest rate	7.875%
2016 7 7/8% Senior Unsecured Notes \| Senior Unsecured Notes \| Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note value	$ 489,323
2016 7 7/8% Senior Unsecured Notes \| Senior Unsecured Notes \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note value	$ 466,875

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

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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
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

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

- Definition

Fair value portion of contractual arrangement with a lender under which borrowings can be made up to a specific amount at any point in time.

+ References

No definition available.

+ Details

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

- Definition

Fair value portion of notes payable.

+ 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 210.5-02.19,20,22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=mtga_SeniorSecuredCreditFacilityRevolvingMaturingOctober2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mtga_SeniorSecuredCreditFacilityTermLoanAMaturingOctober2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mtga_SeniorSecuredCreditFacilityTermLoanBMaturingOctober2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mtga_A2016SeniorUnsecuredNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: