The amount of interest payable and waived interest due to related party.

No definition available.

Name:	mdgl_InterestPayableAndWaivedInterestRelatedPartyCurrent
Namespace Prefix:	mdgl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of interest payable due to related party.

+ References

No definition available.

+ Details

Name:	mdgl_InterestPayableRelatedPartyCurrent
Namespace Prefix:	mdgl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of interest payable waived due to related party.

+ References

No definition available.

+ Details

Name:	mdgl_InterestPayableWaivedRelatedPartyCurrent
Namespace Prefix:	mdgl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The value of financial instruments that the original debt payable to related party is being converted into in a non cash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

No definition available.

+ Details

Name:	mdgl_RelatedPartyTransactionsDebtConversionConvertedInstrumentAmount
Namespace Prefix:	mdgl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from a long-term borrowing made from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth. Alternate caption: Proceeds from Advances from Affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3255-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

Name:	us-gaap_ProceedsFromRelatedPartyDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Identify the stated interest rate per the agreement, for example, leasing and debt arrangements between related parties.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_ConvertibleNotesPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mdgl_AmendedAndRestatedMarch12016ConvertiblePromissoryNotesPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mdgl_LenderDMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Convertible Promissory Notes - Related Parties (Details) - USD ($)		3 Months Ended		5 Months Ended
	Apr. 13, 2016	Mar. 31, 2017	Mar. 31, 2016	Jul. 22, 2016	Dec. 31, 2016
Cash received			$ 750,000
Conversion option on promissory notes - related parties
Interest rate		8.00%
Total accrued and waived interest	$ 13,680,000
Accrued interest					$ 2,456,000
Net waived interest recorded as an increase to APIC	11,224,000
Amended And Restated March 1, 2016 Notes
Cash received				$ 8,500,000
Lender D \| Amended And Restated March 1, 2016 Notes
Conversion amount	$ 500,000