Represents term of option to extend credit facility after the maturity date specified in the agreement.

No definition available.

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

- Definition

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84164817&loc=d3e45280-112737

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

General - Long Term Debt and Finance Lease Obligation (Details) - USD ($) $ in Millions			3 Months Ended
	Aug. 13, 2018	Sep. 22, 2017	Mar. 31, 2019	Dec. 31, 2018
Debt disclosures
Finance lease and deferred financing obligations			$ 31.6	$ 31.2
Deferred loan issuance cost			6.8	5.9
Gross cost of finance leased assets			55.6	51.9
4.400% Senior Notes due 2024
Long Term Debt, Capital Lease and Deferred Financing Obligations
Aggregate principal amount of Senior Notes		$ 400.0	399.3	399.3
Stated interest rate (as a percent)		4.40%
Redemption price as a percentage of the principal amount being redeemed		100.00%
2017 Credit Agreement
Long Term Debt, Capital Lease and Deferred Financing Obligations
Term of option to extend credit facility	1 year
Debt disclosures
Available borrowing capacity			$ 400.0
2017 Credit Agreement \| Revolving Loan borrowings
Long Term Debt, Capital Lease and Deferred Financing Obligations
Maximum borrowing capacity		$ 400.0
Commitment commission (as a percent)			0.20%
2017 Credit Agreement \| Term Loan
Long Term Debt, Capital Lease and Deferred Financing Obligations
Maximum borrowing capacity		$ 350.0
Weighted average interest rate (as a percent)			4.2609%
Long-term Debt, Fiscal Year Maturity
2019			$ 13.1
2020			17.5
2021			17.5
2022			17.5
2023			258.1
2017 Credit Agreement \| Prime rate
Long Term Debt, Capital Lease and Deferred Financing Obligations
Basis spread on variable rate (as a percent)		0.50%
2017 Credit Agreement \| Overnight Federal Funds rate
Long Term Debt, Capital Lease and Deferred Financing Obligations
Basis spread on variable rate (as a percent)		0.50%
2017 Credit Agreement \| Eurodollar rate for one month
Long Term Debt, Capital Lease and Deferred Financing Obligations
Basis spread on variable rate (as a percent)		1.00%
2017 Credit Agreement \| Eurodollar rate for selected interest period
Long Term Debt, Capital Lease and Deferred Financing Obligations
Basis spread on variable rate (as a percent)		1.50%
Standby Letters of Credit with The Bank Of Tokyo-Mitsubishi UFJ, Ltd.
Debt disclosures
Letters of credit outstanding			$ 66.4	$ 66.1