Business Combinations - Total Acquisition Date Fair Value (Details) - USD ($) $ in Thousands			12 Months Ended
	Aug. 17, 2015	Nov. 12, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Fair value of AMAG common stock issued			$ 0	$ 0	$ 111,964
Total Acquisition Date Fair Value
Goodwill			$ 639,484	$ 639,188	$ 205,824
CBR
Business Acquisition [Line Items]
Cash consideration	$ 700,000
Estimated working capital, indebtedness and other adjustments	(17,837)
Purchase price paid at closing	682,163
Cash paid on finalization of the net working capital, indebtedness and other adjustments	193
Total purchase price	682,356
Total Acquisition Date Fair Value
Accounts receivable	8,660
Inventories	3,825
Prepaid and other current assets	8,480
Restricted cash - short-term	30,752
Property, plant and equipment	29,401
Deferred income tax assets	5,062
Other long-term assets	496
Accounts payable	(2,853)
Accrued expenses	(13,770)
Deferred revenues - short-term	(3,100)
Payable to former CBR shareholders	(37,947)
Deferred income tax liabilities	(149,873)
Other long-term liabilities	(506)
Total estimated identifiable net assets	240,985
Goodwill	441,371
Total	682,356
CBR | Customer relationships
Total Acquisition Date Fair Value
Finite-lived intangible assets	297,000
CBR | Favorable lease asset
Total Acquisition Date Fair Value
Finite-lived intangible assets	358
CBR | CBR Trade Names and Trademarks
Total Acquisition Date Fair Value
Indefinite-lived intangible assets	$ 65,000
Lumara Health
Business Acquisition [Line Items]
Cash consideration		$ 600,000
Fair value of AMAG common stock issued		111,964
Fair value of contingent milestone payments		205,000
Estimated working capital, indebtedness and other adjustments		821
Purchase price paid at closing		917,785
Cash received on finalization of the net working capital and other adjustments		(562)
Cash acquired from Lumara Health		(5,219)
Total purchase price		912,004
Total Acquisition Date Fair Value
Accounts receivable		36,852
Inventories		30,300
Prepaid and other current assets		3,322
Restricted cash - short-term		1,997
Property, plant and equipment		60
Deferred income tax assets		102,355
Other long-term assets		3,412
Accounts payable		(3,807)
Accrued expenses		(36,561)
Deferred income tax liabilities		(295,676)
Other long-term liabilities		(4,563)
Total estimated identifiable net assets		713,891
Goodwill		198,113
Total		912,004
Lumara Health | Makena base technology
Total Acquisition Date Fair Value
Finite-lived intangible assets		797,100
Lumara Health | IPR&D
Total Acquisition Date Fair Value
Indefinite-lived intangible assets		$ 79,100