Represents the expected development period from the effective date of agreement.

No definition available.

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- Definition

Represents the cumulative amount of milestone payment received during the period under the terms of license and collaboration agreements.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Represents the cumulative amount of nonrefundable, noncreditable upfront license fee received during the period under the terms of license and collaboration agreements.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Revenue recognized during the period related to spending in excess of collaboration agreement budget for services performed

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Represents the maximum cumulative amount of milestone payments that can be received over the life of the license and collaboration agreements.

+ References

No definition available.

+ Details

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- Definition

Potential milestone payments receivable.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Spending in excess of a collaborations budget incurred during a period.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the date a license and collaboration agreement is scheduled to terminate.

+ References

No definition available.

+ Details

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Data Type:	xbrli:dateItemType
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- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19-26)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Balance Type:	credit
Period Type:	instant

- Definition

Revenue from multiple-deliverable arrangements that include licensing fees and services revenue. Licensing revenue is consideration received from another party for the right to use, but not own, certain of the entity's intangible assets. Licensing arrangements include, but are not limited to, rights to use a patent, copyright, technology, manufacturing process, software or trademark. Licensing fees are generally, but not always, fixed as to amount and not dependent upon the revenue generated by the licensing party. An entity may receive licensing fees for licenses that also generate royalty payments to the entity. Services revenue may be derived by providing other, nonspecified, services during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(d),(e))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_CounterpartyNameAxis=mack_IpsenSAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=mack_AssetPurchaseAndSaleAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DeferredRevenueArrangementTypeAxis=mack_DevelopmentAndCommercializationMilestonesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DeferredRevenueArrangementTypeAxis=mack_SaleMilestoneInMajorEuropeanCountriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DeferredRevenueArrangementTypeAxis=mack_SaleMilestoneInMajorNonEuropeanAndNonAsianCountryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DeferredRevenueArrangementTypeAxis=mack_ClinicalTrialsInLungCancerMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_CounterpartyNameAxis=mack_SanofiMember
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- Details

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License and Collaboration Agreements - Additional Information (Detail) - USD ($)			12 Months Ended
	Apr. 03, 2017	Nov. 10, 2009	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Agreement termination scheduled date			Dec. 17, 2014
Assets maintained related to Sanofi Agreement			$ 81,483,000	$ 234,880,000
Liabilities maintained related to Sanofi Agreement			334,142,000	418,569,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Development and Commercialization Milestones [Member] \| Subsequent Event [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum amount of milestone payments that can be received	$ 33,000,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Sale Milestones in Major European Countries [Member] \| Subsequent Event [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments receivable	18,000,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Sale Milestones in Major Non-European and Non-Asian Country [Member] \| Subsequent Event [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments receivable	5,000,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Clinical Trials in Lung Cancer [Member] \| Subsequent Event [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments receivable	$ 10,000,000
Sanofi [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront license fee received		$ 60,000,000
Milestone license fee received			25,000,000
Expected development period from the effective date of agreement		12 years
License and collaboration revenues			0	0
Assets maintained related to Sanofi Agreement			0	0
Liabilities maintained related to Sanofi Agreement			$ 0	$ 0
Sanofi [Member] \| License and Collaboration Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License and collaboration revenues					$ 92,296,000
Recognized revenue related to excess spending					$ 5,800,000
Spending in excess of budget						$ 10,100,000