General - Leases - Maturity Dates (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Leases
2020	$ 14,695
2021	18,349
2022	17,297
2023	11,922
2024	10,040
2025 and beyond	4,658
Total lease payments	76,961
Less interest	(1,913)
Present value of lease liabilities	$ 75,048

Present value of lessee's discounted obligation for lease payments from operating and finance leases.

No definition available.

Name:	mgln_LeaseLiability
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments for operating and finance leases.

+ References

No definition available.

+ Details

Name:	mgln_LeaseLiabilityPaymentsDue
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments for operating and finance lease, due after fifth fiscal year following latest fiscal year.

+ References

No definition available.

+ Details

Name:	mgln_LeaseLiabilityPaymentsDueAfterYearFive
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments for operating and finance lease, due in fifth fiscal year following latest fiscal year.

+ References

No definition available.

+ Details

Name:	mgln_LeaseLiabilityPaymentsDueYearFive
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments for operating and finance lease, due in fourth fiscal year following latest fiscal year.

+ References

No definition available.

+ Details

Name:	mgln_LeaseLiabilityPaymentsDueYearFour
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments for operating and finance lease, due in third fiscal year following latest fiscal year.

+ References

No definition available.

+ Details

Name:	mgln_LeaseLiabilityPaymentsDueYearThree
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments for operating and finance lease, due in second fiscal year following latest fiscal year.

+ References

No definition available.

+ Details

Name:	mgln_LeaseLiabilityPaymentsDueYearTwo
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments for operating and finance lease, due in remainder of fiscal year following latest fiscal year ended.

+ References

No definition available.

+ Details

Name:	mgln_LeaseLiabilityPaymentsRemainderOfFiscalYear
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for operating and finance leases.

+ References

No definition available.

+ Details

Name:	mgln_LeaseLiabilityUndiscountedExcessAmount
Namespace Prefix:	mgln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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