Additional cash received from collaborators to reimburse certain expenses.

No definition available.

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Namespace Prefix:	amag_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the product sales and royalty revenue recognized under the agreement.

+ References

No definition available.

+ Details

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

- Definition

Represents the potential milestone payments expected to be received by the entity under the collaboration agreement.

+ References

No definition available.

+ Details

Name:	amag_CollaborativeArrangementsPotentialMilestonePaymentsExpectedToBeReceived
Namespace Prefix:	amag_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Cummulated non-substantive milestone payments received from collaborative arrangement as of reporting time.

+ References

No definition available.

+ Details

Name:	amag_Nonsubstantivemilestonepaymentsreceived
Namespace Prefix:	amag_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The number of years over which the amount of previously reported deferred or unearned revenue is recognized as revenue.

+ References

No definition available.

+ Details

Name:	amag_RecognitionOfDeferredRevenueAmortizationPeriod
Namespace Prefix:	amag_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Cummulated upfront payments received from collaborators as of the reporting time.

+ References

No definition available.

+ Details

Name:	amag_UpfrontPaymentsReceivedFromCollaborators
Namespace Prefix:	amag_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Sum of the carrying amounts of deferred costs that are expected to be recognized as a charge against earnings in periods after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 17

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.10)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DeferredCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Sum of the carrying amounts as of the balance sheet date of deferred costs capitalized at the end of the reporting period that are expected to be charged against earnings within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.8)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DeferredCostsCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The carrying amount of deferred costs.

+ References

No definition available.

+ Details

Name:	us-gaap_DeferredCostsCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 13

-Section A

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 13.A.4(a).Q1 Response)

-URI http://asc.fasb.org/extlink&oid=27012821&loc=d3e214044-122780

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 13.A.4(a).Q1)

-URI http://asc.fasb.org/extlink&oid=27012821&loc=d3e214044-122780

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 8

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6935-107765

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 13

-Section A

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The noncurrent portion of deferred revenue amount as of balance sheet date. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized, and is not expected to be recognized in the next twelve months. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References

+ Details

Name:	us-gaap_DeferredRevenueNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of previously reported deferred or unearned revenue that was recognized as revenue during the period. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Cash received from collaborators during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Repayment received or receivable for expenses incurred on behalf of a client or customer, other than those reimbursements received by landlords from tenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 45

-Section 45

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=21915142&loc=d3e60722-111653

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Collaborative Agreements (Details) (USD $)			1 Months Ended		3 Months Ended	6 Months Ended	12 Months Ended				6 Months Ended	12 Months Ended
Collaborative Agreements (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Apr. 30, 2010 License Development And Commercialization Agreement With Takeda [Member]	Mar. 31, 2010 License Development And Commercialization Agreement With Takeda [Member]	Jun. 30, 2014 License Development And Commercialization Agreement With Takeda [Member]	Jun. 30, 2014 License Development And Commercialization Agreement With Takeda [Member]	Dec. 31, 2010 License Development And Commercialization Agreement With Takeda [Member]	Jun. 30, 2014 License Development And Commercialization Agreement With Takeda [Member] Maximum [Member]	Jun. 30, 2014 License Development And Commercialization Agreement With Takeda [Member] Upfront Payment And Non Substantive Milestone Payments Received [Member]	Jun. 30, 2014 License Development And Commercialization Agreement With Takeda [Member] Product Shipped But Not Yet Sold [Member]	Jun. 30, 2014 Collaboration And Exclusive License Agreement With3 S Bio Inc [Member]	Dec. 31, 2008 Collaboration And Exclusive License Agreement With3 S Bio Inc [Member]
Collaborative Agreements
Upfront payment received			$ 60,000,000									$ 1,000,000
Additional upfront payment							1,000,000
Period of recognition of deferred revenues				10 years
Milestone payments expected to be received under the agreement								186,000,000
Deferred revenue recognized in earnings related to upfront payments					2,000,000	3,900,000					1,000,000
Other reimbursement revenues					100,000	300,000
Product sales and royalty revenue recognized					200,000	400,000
Total upfront payments received									61,000,000
Total non-substantive milestone payments received									18,000,000
Deferred revenues									45,400,000	2,200,000
Deferred revenues, short-term	9,222,000	8,226,000							7,900,000	1,300,000
Deferred revenues, long-term	38,360,000	44,534,000							37,500,000	900,000
Deferred costs					2,000,000	2,000,000
Deferred costs, short-term					1,200,000	1,200,000
Deferred costs, long-term					$ 800,000	$ 800,000