Represents term of option to extend credit facility after the maturity date specified in the agreement.

No definition available.

Name:	mgln_AdditionalPeriodOfCreditFacility
Namespace Prefix:	mgln_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The borrowing margin percentage rate, to which the higher of two alternative variable rates is added.

+ References

No definition available.

+ Details

Name:	mgln_BorrowingMarginPercent
Namespace Prefix:	mgln_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The effective borrowing margin percentage rate, to which the higher of two alternative variable rates is added.

+ References

No definition available.

+ Details

Name:	mgln_EffectiveBorrowingMarginPercent
Namespace Prefix:	mgln_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737

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(22))
-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 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Definition

Amount before accumulated depreciation of leased physical assets used in the normal conduct of business to produce goods and services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6455314&loc=d3e45014-112735

+ Details

Name:	us-gaap_CapitalLeasedAssetsGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

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

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
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

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

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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 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

+ 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

+ 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

+ 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

- References

No definition available.

+ Details

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

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

+ Details

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

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

+ Details

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

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

No definition available.

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Details

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

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CurrencyAxis=currency_EUR
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=mgln_RevolvingAndTermLoanBorrowingsMember
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_DebtInstrumentAxis=mgln_Creditfacility2014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=mgln_CreditFacility2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=mgln_TermLoan2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mgln_CreditFacility2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long-Term Debt and Capital Lease Obligations (Details) - USD ($) $ in Thousands				12 Months Ended
	Jan. 10, 2017	Sep. 30, 2014	Jul. 23, 2014	Dec. 31, 2016	Dec. 31, 2014	Feb. 22, 2017	Jun. 27, 2016	Dec. 31, 2015
Long-term Debt and Capital Lease Obligations
Proceeds from issuance of debt				$ 375,000	$ 250,000
Capital lease obligations				26,000				$ 24,400
Gross cost of capital leased assets				41,700				39,300
Revolving Loan borrowings
Long-term Debt and Capital Lease Obligations
Revolving borrowings outstanding								0
Term Loan
Long-term Debt and Capital Lease Obligations
Available borrowing capacity				218,700
Long-term Debt, Fiscal Year Maturity
2017				225,000
2018				25,000
2019				168,700
Term Loan \| Subsequent event
Long-term Debt and Capital Lease Obligations
Commitment commission (as a percent)	0.25%
Letter of Credit
Long-term Debt and Capital Lease Obligations
Letters of credit outstanding				33,700				$ 33,400
Eurodollar denominated loans \| Revolving Loan borrowings
Long-term Debt and Capital Lease Obligations
Revolving borrowings outstanding				$ 175,000
Eurodollar denominated loans \| Eurodollar rate for selected interest period \| Revolving and Term Loan Borrowings \| Minimum
Long-term Debt and Capital Lease Obligations
Borrowing margin (as a percent)				1.50%
Eurodollar denominated loans \| Eurodollar rate for selected interest period \| Revolving and Term Loan Borrowings \| Maximum
Long-term Debt and Capital Lease Obligations
Borrowing margin (as a percent)				2.00%
2014 Credit Facility
Long-term Debt and Capital Lease Obligations
Maximum borrowing capacity			$ 500,000
Term of option to extend credit facility			1 year
2014 Credit Facility \| Subsequent event
Long-term Debt and Capital Lease Obligations
Available borrowing capacity						$ 222,300
2014 Credit Facility \| Revolving Loan borrowings
Long-term Debt and Capital Lease Obligations
Maximum borrowing capacity			$ 250,000
2014 Credit Facility \| Revolving Loan borrowings \| Minimum
Long-term Debt and Capital Lease Obligations
Commitment commission (as a percent)				0.20%
2014 Credit Facility \| Revolving Loan borrowings \| Maximum
Long-term Debt and Capital Lease Obligations
Commitment commission (as a percent)				0.35%
2014 Credit Facility \| Term Loan
Long-term Debt and Capital Lease Obligations
Maximum borrowing capacity			250,000
2014 Credit Facility \| Letter of Credit
Long-term Debt and Capital Lease Obligations
Maximum borrowing capacity			$ 70,000
2014 Credit Facility \| Letter of Credit \| Minimum
Long-term Debt and Capital Lease Obligations
Stated interest rate (as a percent)				1.50%
2014 Credit Facility \| Letter of Credit \| Maximum
Long-term Debt and Capital Lease Obligations
Stated interest rate (as a percent)				2.00%
2014 Credit Facility \| Overnight Federal Funds rate \| Revolving and Term Loan Borrowings \| Minimum
Long-term Debt and Capital Lease Obligations
Borrowing margin (as a percent)				0.50%
2014 Credit Facility \| Overnight Federal Funds rate \| Revolving and Term Loan Borrowings \| Maximum
Long-term Debt and Capital Lease Obligations
Borrowing margin (as a percent)				1.00%
2014 Credit Facility \| Eurodollar rate for one month \| Revolving and Term Loan Borrowings
Long-term Debt and Capital Lease Obligations
Basis spread on variable rate (as a percent)				1.00%
2014 Credit Facility \| Eurodollar denominated loans \| Eurodollar rate for selected interest period \| Term Loan
Long-term Debt and Capital Lease Obligations
Proceeds from issuance of debt		$ 250,000
Effective borrowing margin (as a percent)				1.625%
Effective interest rate (as a percent)				2.395%
Weighted average interest rate (as a percent)				2.034%
2016 Credit Facility \| 2016 Term Loan
Long-term Debt and Capital Lease Obligations
Maximum borrowing capacity							$ 200,000
2016 Credit Facility \| Overnight Federal Funds rate \| Term Loan \| Minimum
Long-term Debt and Capital Lease Obligations
Borrowing margin (as a percent)				0.25%
2016 Credit Facility \| Overnight Federal Funds rate \| Term Loan \| Maximum
Long-term Debt and Capital Lease Obligations
Borrowing margin (as a percent)				0.75%
2016 Credit Facility \| Eurodollar rate for one month \| Term Loan
Long-term Debt and Capital Lease Obligations
Basis spread on variable rate (as a percent)				1.00%
2016 Credit Facility \| Eurodollar denominated loans \| Eurodollar rate for selected interest period \| Term Loan
Long-term Debt and Capital Lease Obligations
Effective borrowing margin (as a percent)				1.375%
Effective interest rate (as a percent)				2.145%
Weighted average interest rate (as a percent)				1.901%
2016 Credit Facility \| Eurodollar denominated loans \| Eurodollar rate for selected interest period \| Term Loan \| Minimum
Long-term Debt and Capital Lease Obligations
Borrowing margin (as a percent)				1.25%
2016 Credit Facility \| Eurodollar denominated loans \| Eurodollar rate for selected interest period \| Term Loan \| Maximum
Long-term Debt and Capital Lease Obligations
Borrowing margin (as a percent)				1.75%
2017 Credit Facility \| Subsequent event
Long-term Debt and Capital Lease Obligations
Available borrowing capacity						$ 100,000
2017 Credit Facility \| Overnight Federal Funds rate \| Subsequent event
Long-term Debt and Capital Lease Obligations
Basis spread on variable rate (as a percent)	0.50%
2017 Credit Facility \| Overnight Federal Funds rate \| Term Loan \| Subsequent event
Long-term Debt and Capital Lease Obligations
Basis spread on variable rate (as a percent)	0.625%
2017 Credit Facility \| Eurodollar rate for one month \| Term Loan \| Subsequent event
Long-term Debt and Capital Lease Obligations
Basis spread on variable rate (as a percent)	1.00%
2017 Credit Facility \| Eurodollar rate for selected interest period \| Term Loan \| Subsequent event
Long-term Debt and Capital Lease Obligations
Borrowing margin (as a percent)	1.625%