Nature of the Business - Additional Information (Detail)	3 Months Ended
Mar. 31, 2015 Candidate
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of novel therapeutic oncology candidates	6

Represents the number of novel therapeutic oncology candidates in clinical development of the entity.

No definition available.

Name:	mack_NumberOfNovelTherapeuticOncologyCandidatesInClinicalDevelopment
Namespace Prefix:	mack_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration