Amount of additional debt contingently available to the entity.

No definition available.

Name:	mack_DebtInstrumentAdditionalAdvanceAmount
Namespace Prefix:	mack_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the non-current portion of the discount recorded in accordance with the loan agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	mack_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt instrument extended maturity period.

+ References

No definition available.

+ Details

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Namespace Prefix:	mack_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the extension period for interest only payments as provided under the loan agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	mack_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

+ Details

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

- Definition

End date of debt instrument redemption period, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph e

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

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Balance Type:	na
Period Type:	duration

- Definition

Start date of debt instrument redemption period, in CCYY-MM-DD format.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

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-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

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

- Definition

Amount of the cost of borrowed funds accounted for as interest expense.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

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-Subparagraph (SX 210.9-04.9)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 9

-Article 9

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

- Details

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Borrowings - Loan Agreement - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended		0 Months Ended
	Nov. 06, 2014	Mar. 31, 2015	Mar. 31, 2014	Feb. 25, 2015	Nov. 30, 2012
Schedule Of Debt Instruments [Line Items]
Extension period for interest-only payment	4 months
Interest expense		$ 4,566,000us-gaap_InterestExpense	$ 4,511,000us-gaap_InterestExpense
Loan and Security Agreement [Member]
Schedule Of Debt Instruments [Line Items]
Discount on loan recorded as a non-current liability to be paid upon full repayment or maturity of the loans		1,200,000
Interest expense		1,200,000	1,200,000
Hercules [Member]
Schedule Of Debt Instruments [Line Items]
Less unamortized discount		1,600,000
Hercules [Member] \| Loan and Security Agreement [Member]
Schedule Of Debt Instruments [Line Items]
Aggregate principal amount of loans received				40,000,000	40,000,000
Outstanding principal balance repayment period				Jun. 01, 2016
Outstanding principal balance repayment period				Nov. 01, 2018
Extended maturity period on principal payment				6 months
Additional term loan advance by company				$ 15,000,000