Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013
Operating Leases
Aggregate rent due over amended term of lease	$ 2.6
Additional reimbursement for tenant improvements agreed by landlord per lease amendment	0.6
Aggregate landlord reimbursable tenant improvements outstanding under the existing lease and the lease amendment	$ 6.8

Represents the amount of required minimum rental payments for leases having an initial or remaining non-cancelable term in excess of one year related to the lease amendment.

No definition available.

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