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Equity-Based Compensation (Details) (USD $)
12 Months Ended 1 Months Ended 0 Months Ended 1 Months Ended
Dec. 31, 2014
item
Dec. 31, 2013
Dec. 31, 2012
Feb. 28, 2013
May 31, 2013
May 31, 2010
May 31, 2009
Nov. 12, 2014
Dec. 31, 2014
Aug. 31, 2014
Equity-Based Compensation                    
Number of equity compensation plans 3amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfEquityCompensationPlans                  
Equity compensation plans                    
Total equity-based compensation expense $ 8,625,000us-gaap_AllocatedShareBasedCompensationExpense $ 8,004,000us-gaap_AllocatedShareBasedCompensationExpense $ 7,024,000us-gaap_AllocatedShareBasedCompensationExpense              
Employee and Non Employee Stock Option [Member]                    
Equity compensation plans                    
Number of stock options outstanding (in shares) 2,996,383us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= amag_EmployeeAndNonEmployeeStockOptionMember
2,819,676us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= amag_EmployeeAndNonEmployeeStockOptionMember
            2,996,383us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= amag_EmployeeAndNonEmployeeStockOptionMember
 
Granted (in shares) 1,391,776us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= amag_EmployeeAndNonEmployeeStockOptionMember
                 
Forfeited (in shares) (720,493)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod
/ us-gaap_AwardTypeAxis
= amag_EmployeeAndNonEmployeeStockOptionMember
                 
Expense recognition period 2 years                  
Restricted Stock Units (RSUs) [Member]                    
Equity compensation plans                    
Number of restricted stock units outstanding (in shares) 541,226us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
465,394us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
            541,226us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Granted (in shares) 356,626us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
                 
Vested (in shares) (151,518)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
                 
Forfeited (in shares) (129,276)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
                 
Expense recognition period 2 years                  
Restricted Stock Units (RSUs) [Member] | Senior Management [Member]                    
Equity compensation plans                    
Award vesting period       3 years            
Granted (in shares)       82,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
           
Expense recognition period       3 years            
Restricted Stock Units (RSUs) [Member] | Senior Management [Member] | Maximum                    
Equity compensation plans                    
Fair value of awards issued       700,000amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
           
Equity Incentive Plan 2007 [Member]                    
Equity compensation plans                    
Shares authorized for issuance         1,100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
800,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
600,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
     
Number of options and restricted stock units granted since inception (in shares) 7,414,752amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitsGrantsInPeriodSincePlanInception
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
              7,414,752amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitsGrantsInPeriodSincePlanInception
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
 
Number of stock options expired or terminated since inception (in shares) 3,112,356amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsAndTerminationsSincePlanInception
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
              3,112,356amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsAndTerminationsSincePlanInception
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
 
Number of restricted stock units forfeited since inception (in shares) 703,124amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedSincePlanInception
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
              703,124amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedSincePlanInception
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
 
Stock options exercised since inception (in shares) 610,297amag_StockIssuedSinceInceptionSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
              610,297amag_StockIssuedSinceInceptionSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
 
Shares of common stock issued pursuant to vested restricted stock units since inception 577,132amag_StockIssuedSinceInceptionSharesRestrictedStockUnitsVested
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
                 
Number of stock options outstanding (in shares) 2,051,017us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
              2,051,017us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
 
Number of restricted stock units outstanding (in shares) 360,826us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
              360,826us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
 
Remaining number of shares available for future grants 1,707,989us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
              1,707,989us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
 
Equity Incentive Plan 2007 [Member] | Employee and Non Employee Stock Option [Member]                    
Equity compensation plans                    
Reduction in number of shares available for issuance             1amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardReductionInNumberOfSharesAvailableForIssuance
/ us-gaap_AwardTypeAxis
= amag_EmployeeAndNonEmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
     
Equity Incentive Plan 2007 [Member] | Employee and Non Employee Stock Option [Member] | Minimum [Member]                    
Equity compensation plans                    
Expiration term 7 years                  
Equity Incentive Plan 2007 [Member] | Employee and Non Employee Stock Option [Member] | Maximum                    
Equity compensation plans                    
Expiration term 10 years                  
Equity Incentive Plan 2007 [Member] | Restricted Stock Units (RSUs) [Member]                    
Equity compensation plans                    
Reduction in number of shares available for issuance             1.5amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardReductionInNumberOfSharesAvailableForIssuance
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= amag_EquityIncentivePlan2007Member
     
Award vesting period 4 years                  
Stock 2000 Plan                    
Equity compensation plans                    
Number of options and restricted stock units granted since inception (in shares) 2,182,700amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitsGrantsInPeriodSincePlanInception
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
              2,182,700amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitsGrantsInPeriodSincePlanInception
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
 
Number of stock options expired or terminated since inception (in shares) 1,049,339amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsAndTerminationsSincePlanInception
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
              1,049,339amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsAndTerminationsSincePlanInception
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
 
Number of restricted stock units forfeited since inception (in shares) 1,500amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedSincePlanInception
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
              1,500amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedSincePlanInception
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
 
Stock options exercised since inception (in shares) 1,054,095amag_StockIssuedSinceInceptionSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
              1,054,095amag_StockIssuedSinceInceptionSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
 
Shares of common stock issued pursuant to vested restricted stock units since inception 42,500amag_StockIssuedSinceInceptionSharesRestrictedStockUnitsVested
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
                 
Number of stock options outstanding (in shares) 35,266us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
              35,266us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
 
Number of restricted stock units outstanding (in shares) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
              0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
 
Remaining number of shares available for future grants 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
              0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= amag_StockPlan2000Member
 
Stock 2000 Plan | Employee and Non Employee Stock Option [Member]                    
Equity compensation plans                    
Expiration term 10 years                  
Lumara 2013 Plan                    
Equity compensation plans                    
Shares authorized for issuance               200,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= amag_LumaraHealth2013PlanMember
   
Number of options and restricted stock units granted since inception (in shares) 64,000amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitsGrantsInPeriodSincePlanInception
/ us-gaap_PlanNameAxis
= amag_LumaraHealth2013PlanMember
              64,000amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitsGrantsInPeriodSincePlanInception
/ us-gaap_PlanNameAxis
= amag_LumaraHealth2013PlanMember
 
Number of stock options outstanding (in shares) 44,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= amag_LumaraHealth2013PlanMember
              44,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= amag_LumaraHealth2013PlanMember
 
Number of restricted stock units outstanding (in shares) 20,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_PlanNameAxis
= amag_LumaraHealth2013PlanMember
              20,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_PlanNameAxis
= amag_LumaraHealth2013PlanMember
 
Remaining number of shares available for future grants 136,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= amag_LumaraHealth2013PlanMember
              136,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= amag_LumaraHealth2013PlanMember
 
Lumara 2013 Plan | Minimum [Member]                    
Equity compensation plans                    
Expiration term 7 years                  
Lumara 2013 Plan | Maximum                    
Equity compensation plans                    
Expiration term 10 years                  
Other Equity Compensation Grants [Member] | Employee and Non Employee Stock Option [Member] | Senior Management [Member]                    
Equity compensation plans                    
Award vesting period 4 years 4 years                
Granted (in shares) 165,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= amag_EmployeeAndNonEmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
270,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= amag_EmployeeAndNonEmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= amag_EmployeeAndNonEmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
             
Other Equity Compensation Grants [Member] | Employee and Non Employee Stock Option [Member] | Lumara Health Employees [Member]                    
Equity compensation plans                    
Granted (in shares)                 304,600us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= amag_EmployeeAndNonEmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_LumaraHealthEmployeesMember
 
Other Equity Compensation Grants [Member] | Restricted Stock Units (RSUs) [Member] | Senior Management [Member]                    
Equity compensation plans                    
Award vesting period 4 years 4 years                
Granted (in shares) 87,900us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
115,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
            195,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
Fair value of awards issued                   6,300,000amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
Total equity-based compensation expense $ 100,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
                 
Expense recognition period                   3 years
Other Equity Compensation Grants [Member] | Restricted Stock Units (RSUs) [Member] | Lumara Health Employees [Member]                    
Equity compensation plans                    
Granted (in shares)                 22,600us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_LumaraHealthEmployeesMember
 
Other Equity Compensation Grants [Member] | Share Based Compensation Award Vesting At Specific Date One Member | Restricted Stock Units (RSUs) [Member] | Senior Management [Member]                    
Equity compensation plans                    
Vesting rights percentage                   50.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
/ us-gaap_VestingAxis
= amag_ShareBasedCompensationAwardVestingAtSpecificDateOneMember
Other Equity Compensation Grants [Member] | Share Based Compensation Award Vesting At Specific Date Two Member | Restricted Stock Units (RSUs) [Member] | Senior Management [Member]                    
Equity compensation plans                    
Vesting rights percentage                   100.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationGrantsMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amag_SeniorManagementMember
/ us-gaap_VestingAxis
= amag_ShareBasedCompensationAwardVestingAtSpecificDateTwoMember
Other Equity Compensation Plan Outside The 2007 Plan [Member]                    
Equity compensation plans                    
Number of options and restricted stock units granted since inception (in shares) 1,344,000amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitsGrantsInPeriodSincePlanInception
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationPlanOutside2007PlanMember
              1,344,000amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitsGrantsInPeriodSincePlanInception
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationPlanOutside2007PlanMember
 
Number of stock options expired or terminated since inception (in shares) 146,250amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsAndTerminationsSincePlanInception
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationPlanOutside2007PlanMember
              146,250amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsAndTerminationsSincePlanInception
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationPlanOutside2007PlanMember
 
Number of restricted stock units forfeited since inception (in shares) 67,500amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedSincePlanInception
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationPlanOutside2007PlanMember
              67,500amag_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedSincePlanInception
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationPlanOutside2007PlanMember
 
Stock options exercised since inception (in shares) 28,750amag_StockIssuedSinceInceptionSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationPlanOutside2007PlanMember
              28,750amag_StockIssuedSinceInceptionSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationPlanOutside2007PlanMember
 
Shares of common stock issued pursuant to vested restricted stock units since inception 75,000amag_StockIssuedSinceInceptionSharesRestrictedStockUnitsVested
/ us-gaap_PlanNameAxis
= amag_OtherEquityCompensationPlanOutside2007PlanMember