General - Health Care Reform (Details) $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($)
General
HIF fees	$ 29.9

Affordable Care Act (ACA) fiscal year annual fees paid during the period.

No definition available.

Name:	mgln_AffordableCareActFiscalYearAnnualFeesPaidDuringPeriod
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration