Represents the notice period required for termination of contract.

No definition available.

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

- Definition

Represents the term of the contract entered with the customer.

+ References

No definition available.

+ Details

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

- Definition

Represents the term of the renewed contract with the customer.

+ References

No definition available.

+ Details

Name:	mgln_TermOfRenewedContract
Namespace Prefix:	mgln_
Data Type:	xbrli:durationItemType
Balance Type:	na
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

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

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

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

- 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_ConcentrationRiskByTypeAxis=mgln_GeographicConcentrationRiskAreaOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_GovernmentContractsConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorCustomersAxis=mgln_CentersForMedicareAndMedicaidServicesMember
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Summary of Significant Accounting Policies - Concentration of Business (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration of Business
Net revenue	$ 1,694,415	$ 1,419,406	$ 1,419,139	$ 1,305,623	$ 1,263,385	$ 1,292,132	$ 1,164,345	$ 1,117,022	$ 5,838,583	$ 4,836,884	$ 4,597,400
Minimum
Concentration of Business
Term of contracts with customers									1 year
Term of renewal contracts									1 year
Notice period for termination of contract									60 days
Maximum
Concentration of Business
Term of contracts with customers									3 years
Term of renewal contracts									2 years
Notice period for termination of contract									180 days
Pennsylvania Counties
Concentration of Business
Net revenue									$ 490,000	461,600	395,700
Agencies and departments of the United States federal government
Concentration of Business
Net revenue									341,500	252,500	$ 164,300
CMS \| Pennsylvania Counties
Concentration of Business
Net revenue									$ 511,000	$ 272,800