Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 03, 2019
Document and Entity Information
Entity Registrant Name	AMAG PHARMACEUTICALS INC.
Entity Central Index Key	0000792977
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding (in shares)		33,766,939