General - Cash And Cash Equivalents (Details) $ in Millions	Sep. 30, 2018 USD ($)
Cash and Cash Equivalents
Excess capital and undistributed earnings for regulated subsidiaries included in cash and cash equivalents	$ 134.2

Represents the amount of excess capital and undistributed earnings for regulated subsidiaries which are included in cash and cash equivalents.

No definition available.

Name:	mgln_ExcessCapitalAndUndistributedEarningsIncludedInCashAndCashEquivalents
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant