Business Combination (Details 2) - USD ($) $ in Thousands		6 Months Ended
	Nov. 12, 2014	Jun. 30, 2015	Dec. 31, 2014
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Goodwill		$ 204,414	$ 205,824
Lumara Health
Business Acquisition [Line Items]
Cash consideration	$ 600,000	600,000
Fair value of 3.2 million shares of AMAG common stock		111,964
Fair value of contingent milestone payments		205,000
Estimated working capital and other adjustments		821
Purchase price paid at closing		917,785
Due from sellers		(562)
Cash acquired from Lumara Health		(5,219)
Total purchase price paid		912,004
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Accounts receivable		36,852
Inventories		30,300
Prepaid and other current assets		3,322
Deferred income tax assets		94,965
Property and equipment		60
Makena marketed product		797,100
IPR & D		79,100
Restricted cash		1,997
Other long-term assets		3,412
Accounts payable		(3,807)
Accrued expenses		(37,499)
Deferred income tax liabilities		(293,649)
Other long-term liabilities		(4,563)
Total estimated identifiable net assets		707,590
Goodwill		204,414	$ 205,800
Total		$ 912,004