Product Revenue Reserves and Allowances - Summary of Product Revenue Reserve and Allowance Categories (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($)
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 540
Provisions related to sales in the current year	8,230
Adjustments related to sales in the prior year	(213)
Credits and payments made	(6,617)
Ending balance	1,940
Trade Allowances [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	138
Provisions related to sales in the current year	1,900
Credits and payments made	(1,507)
Ending balance	531
Rebates and Chargeback Discounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	362
Provisions related to sales in the current year	5,928
Adjustments related to sales in the prior year	(213)
Credits and payments made	(5,077)
Ending balance	1,000
Product Returns [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	32
Provisions related to sales in the current year	397
Credits and payments made	(26)
Ending balance	403
Other Incentives [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	8
Provisions related to sales in the current year	5
Credits and payments made	(7)
Ending balance	$ 6

Valuation allowances and reserves prior year adjustments.

No definition available.

Name:	mack_ValuationAllowancesAndReservesPriorYearAdjustments
Namespace Prefix:	mack_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

+ Details

Name:	us-gaap_ValuationAllowancesAndReservesBalance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, from charges to costs and expenses.

+ References

+ Details

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

- Definition

Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.

+ References

+ Details

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

- 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

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

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=us-gaap_AllowanceForTradeReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=mack_RebatesAndChargeBackDiscountsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=us-gaap_AllowanceForSalesReturnsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=mack_OtherIncentivesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: