Description of Business (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2012
Description of Business
Payment made to licensees	$ 1.6
Takeda Agreement
Description of Business
Milestone payments earned under the agreement	$ 15.0	$ 15.0

The total amount of contingent milestone payments earned to date pursuant to the collaboration agreement.

No definition available.

Name:	amag_CollaborativeArrangementMilestonePaymentsEarned
Namespace Prefix:	amag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration