Discontinued Operations - Components of Income from Discontinued Operations - Additional Information (Details) - MCC Business - Discontinued Operations, Held-for-sale - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Discontinued Operations
Stock compensation expense	$ 397	$ 207	$ 1,023	$ 621
Changes in fair value of contingent consideration		$ 4		$ (2,001)
Divestiture related expenses	$ 2,195		$ 6,154

Amount of changes in fair value of contingent consideration attributable to disposal group, including, but not limited to, discontinued operation.

No definition available.

Name:	mgln_DisposalGroupIncludingDiscontinuedOperationIncreaseDecreaseInFairValueOfConsideration
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration