Summary of Significant Accounting Policies (Details 2) (Minimum)	12 Months Ended
Dec. 31, 2012
Minimum
Marketable Securities
Expected average maturities period of marketable securities classified as available-for-sale	3 months

Represents the expected average maturity period of marketable securities classified as available-for-sale.

No definition available.

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