Business Combination (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions		3 Months Ended	6 Months Ended
	Nov. 12, 2014	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01	$ 0.01
Future contingent payments, maximum	$ 350,000
Final settlement adjustment		$ 600
Lumara Health
Business Acquisition [Line Items]
Ownership percentage acquired	100.00%
Cash consideration	$ 600,000		$ 600,000
Shares of AMAG common stock issued in business combination	3.2
Fair value of 3.2 million shares of AMAG common stock			$ 111,964
Final settlement adjustment		$ 4,500
Lumara Health | Common Stock
Business Acquisition [Line Items]
Common stock, par value (in dollars per share)	$ 0.01