Accrued Interest Payable, Including Commitment Fees

No definition available.

Name:	mtga_AccruedInterestPayableIncludingCommitmentFees
Namespace Prefix:	mtga_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt Instrument, Amortization Of Principal, Percentage, Annual

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentAmortizationOfPrincipalPercentageAnnual
Namespace Prefix:	mtga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Amortization Of Principal, Percentage, Year One

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentAmortizationOfPrincipalPercentageYearOne
Namespace Prefix:	mtga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Amortization Of Principal, Percentage, Year Three

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentAmortizationOfPrincipalPercentageYearThree
Namespace Prefix:	mtga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Amortization Of Principal, Percentage, Year Two

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentAmortizationOfPrincipalPercentageYearTwo
Namespace Prefix:	mtga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Exit Fee

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentExitFee
Namespace Prefix:	mtga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Interest Rate, Stated Percentage, Due At Maturity

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentInterestRateStatedPercentageDueAtMaturity
Namespace Prefix:	mtga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Interest Rate, Stated Percentage, Due Monthly

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentInterestRateStatedPercentageDueMonthly
Namespace Prefix:	mtga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Variable Rate Basis, Minimum

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentVariableRateBasisMinimum
Namespace Prefix:	mtga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Variable Rate, Leverage-based Margin

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentVariableRateLeveragebasedMargin
Namespace Prefix:	mtga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Variable Rate at Period End

+ References

No definition available.

+ Details

Name:	mtga_DebtInstrumentVariableRateatPeriodEnd
Namespace Prefix:	mtga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Long-term Debt, Including Due to Related Parties

+ References

No definition available.

+ Details

Name:	mtga_LongTermDebtIncludingDueToRelatedParties
Namespace Prefix:	mtga_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-term Debt, Including Due to Related Parties, Excluding Deferred Income, Gain on Sale of Derivatives, Net

+ References

No definition available.

+ Details

Name:	mtga_LongTermDebtIncludingDueToRelatedPartiesExcludingDeferredIncomeGainOnSaleOfDerivativesNet
Namespace Prefix:	mtga_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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

- Definition

Carrying value as of the balance sheet date of [accrued] interest payable on all forms of debt, including trade payables, that has been incurred and is unpaid. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Current Liabilities

-URI http://asc.fasb.org/extlink&oid=6509677

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.20)

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

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 9

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e7018-107765

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6935-107765

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-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=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

+ Details

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

- 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://www.xbrl.org/2003/role/presentationRef

-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=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-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=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

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

- Details

Name:	us-gaap_VariableRateAxis=mtga_EurodollarRateTermLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_VariableRateAxis=mtga_EurodollarRateRevolvingLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_FederalFundsEffectiveSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=mtga_OneMonthLondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

LONG-TERM DEBT - Credit Facilities (Details) - USD ($)	1 Months Ended	9 Months Ended
LONG-TERM DEBT - Credit Facilities (Details) - USD ($)	Nov. 30, 2013	Jun. 30, 2015	Sep. 30, 2014	Jul. 31, 2012
Debt Instrument [Line Items]
Long-term debt, excluding capital leases		$ 1,679,449,000	$ 1,730,936,000
Accrued interest payable		28,718,000	8,659,000
Credit Facility
Debt Instrument [Line Items]
Accrued interest including commitment fees		166,000	212,000
Senior Secured Credit Facility - Term Loan A \| Credit Facility
Debt Instrument [Line Items]
Debt outstanding		114,100,000
Long-term debt, excluding capital leases		$ 113,654,000	119,789,000
Senior Secured Credit Facility - Term Loan A \| Credit Facility \| Eurodollar Rate Term Loans
Debt Instrument [Line Items]
Basis spread on variable rate		4.25%
Variable rate at period end		0.28%
Senior Secured Credit Facility - Term Loan B, due June 2018, net of discount of $6,780 and $8,337, respectively \| Credit Facility
Debt Instrument [Line Items]
Debt outstanding		$ 719,100,000
Long-term debt, excluding capital leases		$ 712,270,000	716,188,000
Senior Secured Credit Facility - Term Loan B, due June 2018, net of discount of $6,780 and $8,337, respectively \| Credit Facility \| Eurodollar Rate Term Loans
Debt Instrument [Line Items]
Basis spread on variable rate		4.50%
Variable rate at period end		1.00%
Senior Secured Credit Facility - Revolving, due June 2018 \| Credit Facility
Debt Instrument [Line Items]
Debt outstanding		$ 8,000,000
Letters of credit issued		3,000,000
Credit facility outstanding		0
Remaining borrowing capacity		89,000,000
Long-term debt, excluding capital leases		$ 8,000,000	37,000,000
Senior Secured Credit Facility - Revolving, due June 2018 \| Credit Facility \| Eurodollar Rate Revolving Loans [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		4.25%
Long-term debt, excluding capital leases		$ 5,000,000
Variable rate at period end		0.19%
Senior Secured Credit Facility - Revolving, due June 2018 \| Credit Facility \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate		3.25%
Long-term debt, excluding capital leases		$ 3,000,000
Variable rate at period end		3.25%
Line of Credit \| Credit Facility
Debt Instrument [Line Items]
Letters of credit issued		$ 0
Long-term debt, excluding capital leases		0	3,041,000
Borrowing capacity	$ 16,500,000.0
Accrued interest payable		18,000	23,000
Downs Lodging Credit Facility \| Credit Facility
Debt Instrument [Line Items]
Long-term debt, excluding capital leases		45,000,000	45,000,000
Downs Lodging Credit Facility \| Credit Facility \| Downs Lodging, LLC
Debt Instrument [Line Items]
Loan face amount				$ 45,000,000.0
Accrued interest payable		$ 375,000	$ 0
Interest rate				13.00%
Interest due monthly				10.00%
Interest due at maturity				3.00%
Exit fee				3.00%
Senior Secured Notes \| Senior Secured Credit Facilities \| Credit Facility
Debt Instrument [Line Items]
Loan face amount	955,000,000.0
Senior Secured Notes \| Senior Secured Credit Facility - Term Loan A \| Credit Facility
Debt Instrument [Line Items]
Loan face amount	$ 125,000,000
Debt instrument, amortization of principal, percentage, year one	5.00%
Debt instrument, amortization of principal, percentage, year two	7.50%
Debt instrument, amortization of principal, percentage, year three	10.00%
Senior Secured Notes \| Senior Secured Credit Facility - Term Loan A \| Credit Facility \| Minimum
Debt Instrument [Line Items]
Variable rate, leverage-based margin	2.50%
Senior Secured Notes \| Senior Secured Credit Facility - Term Loan A \| Credit Facility \| Maximum
Debt Instrument [Line Items]
Variable rate, leverage-based margin	3.50%
Senior Secured Notes \| Senior Secured Credit Facility - Term Loan A \| Credit Facility \| London Interbank Offered Rate (LIBOR) \| Minimum
Debt Instrument [Line Items]
Variable rate, leverage-based margin	3.50%
Senior Secured Notes \| Senior Secured Credit Facility - Term Loan A \| Credit Facility \| London Interbank Offered Rate (LIBOR) \| Maximum
Debt Instrument [Line Items]
Variable rate, leverage-based margin	4.50%
Senior Secured Notes \| Senior Secured Credit Facility - Term Loan A \| Credit Facility \| Federal Funds Effective Swap Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Senior Secured Notes \| Senior Secured Credit Facility - Term Loan A \| Credit Facility \| One-Month London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Senior Secured Notes \| Senior Secured Credit Facility - Term Loan B, due June 2018, net of discount of $6,780 and $8,337, respectively \| Credit Facility
Debt Instrument [Line Items]
Loan face amount	$ 730,000,000
Debt instrument, amortization of principal, percentage, annual	1.00%
Senior Secured Notes \| Senior Secured Credit Facility - Term Loan B, due June 2018, net of discount of $6,780 and $8,337, respectively \| Credit Facility \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate	4.50%
Variable rate basis, minimum	1.00%
Senior Secured Notes \| Senior Secured Credit Facility - Term Loan B, due June 2018, net of discount of $6,780 and $8,337, respectively \| Credit Facility \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	3.50%
Variable rate basis, minimum	2.00%
Revolving Loans \| Senior Secured Credit Facilities \| Credit Facility
Debt Instrument [Line Items]
Loan face amount	$ 100,000,000
Revolving Loans \| Senior Secured Credit Facility - Term Loan B, due June 2018, net of discount of $6,780 and $8,337, respectively \| Credit Facility
Debt Instrument [Line Items]
Fee assessed on unused revolving credit		0.50%
Revolving Loans \| Senior Secured Credit Facility - Term Loan B, due June 2018, net of discount of $6,780 and $8,337, respectively \| Credit Facility \| Minimum
Debt Instrument [Line Items]
Fee assessed on unused revolving credit	0.375%
Revolving Loans \| Senior Secured Credit Facility - Term Loan B, due June 2018, net of discount of $6,780 and $8,337, respectively \| Credit Facility \| Maximum
Debt Instrument [Line Items]
Fee assessed on unused revolving credit	0.50%