Commitments and Contingencies (Details) (Letter of credit, USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended
Mar. 01, 2013	Mar. 31, 2013
Letter of credit
Commitments And Contingencies [Line Items]
Drawn by landlord from letter of credit		$ 0.38
Maximum liability under standby letter of credit		1.2
Common shares committed to be issued	$ 1.5

The maximum liability under standby letter of credit.

No definition available.

Name:	mrna_StandbyLetterOfCreditMaximumLiability
Namespace Prefix:	mrna_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant