Name:	bpmc_AchievedMilestonePaymentReceivedToBeRecognizedOverPerformancePeriod
Namespace Prefix:	bpmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the cash inflow from achieved milestone payment received, which will be recognized as revenue upon achievement.

No definition available.

Name:	bpmc_AchievedMilestonePaymentReceivedToBeRecognizedUponAchievement
Namespace Prefix:	bpmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The number of deliverables determined per the collaborative agreement.

No definition available.

Name:	bpmc_CollaborativeAgreementNumberOfDeliverables
Namespace Prefix:	bpmc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the aggregate amount of eligible contingent option fees and milestone payments related to specified research, pre-clinical, clinical, regulatory and sales-based milestones.

No definition available.

Name:	bpmc_CollaborativeArrangementEligibleContingentOptionFeesAndMilestonePayments
Namespace Prefix:	bpmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the amount of option fees and milestone payments for research, pre-clinical and clinical development events prior to licensing across all five potential collaboration programs, including contingent milestone payments for initiation of each of the collaboration programs for which the parties will work together to select targets (pre-option exercise milestones).

No definition available.

Name:	bpmc_CollaborativeArrangementEligibleOptionFeesAndMilestonePaymentsPriorToLicensingAcrossAllPrograms
Namespace Prefix:	bpmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The period of time for which written notice is required to be received from the collaborative partner prior to termination of the collaborative agreement.

No definition available.

Name:	bpmc_CollaborativeArrangementPeriodOfPriorNoticeToTerminateAgreement
Namespace Prefix:	bpmc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The royalty term from first commercial sale, option 1.

No definition available.

Name:	bpmc_LicensedProductRoyaltyTermFromFirstCommercialSaleOption1
Namespace Prefix:	bpmc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The royalty term from first commercial sale, option 2.

No definition available.

Name:	bpmc_LicensedProductRoyaltyTermFromFirstCommercialSaleOption2
Namespace Prefix:	bpmc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the amount receivable by the reporting entity from the collaborative partner upon achievement of certain milestones.

No definition available.

Name:	bpmc_MilestoneAchievementPaymentsReceivable
Namespace Prefix:	bpmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Non-substantive milestone payment previously received.

No definition available.

Name:	bpmc_NonSubstantiveMilestonePaymentPreviouslyReceived
Namespace Prefix:	bpmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Non-refundable upfront payment received by the reporting entity from the collaborative partner.

No definition available.

Name:	bpmc_NonrefundableUpfrontPaymentReceived
Namespace Prefix:	bpmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the number of collaboration programs agreed to select targets.

No definition available.

Name:	bpmc_NumberOfAdditionalCollaborationProgramsToSelectTargets
Namespace Prefix:	bpmc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the number of collaboration programs.

No definition available.

Name:	bpmc_NumberOfCollaborationPrograms
Namespace Prefix:	bpmc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the number of collaboration programs with exclusive commercialization rights for licensed products.

No definition available.

Name:	bpmc_NumberOfCollaborationProgramsWithExclusiveCommercializationRights
Namespace Prefix:	bpmc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the number of collaboration programs with agreed upon targets, which are expected to begin in current fiscal year.

No definition available.

Name:	bpmc_NumberOfCollaborationProgramsWithSelectedTargets
Namespace Prefix:	bpmc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the number of collaboration programs in which the entity will retain commercialization rights in the United States for the licensed products, and counterparty will receive commercialization rights outside of the United States for the licensed products.

No definition available.

Name:	bpmc_NumberOfCollaborationProgramsWithSpecifiedCommercializationRights
Namespace Prefix:	bpmc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the number of license option rights to obtain an exclusive license to exploit products derived from the collaboration programs.

No definition available.

Name:	bpmc_NumberOfLicenseOptionRights
Namespace Prefix:	bpmc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the amount of refund provisions with in the collaboration agreement.

No definition available.

Name:	bpmc_RefundProvisionsWithinCollaborationAgreement
Namespace Prefix:	bpmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the amount of reimbursable research and development costs received during the period.

No definition available.

Name:	bpmc_ReimbursableResearchAndDevelopmentCosts
Namespace Prefix:	bpmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the reimbursable research and development costs recognized during the period.

No definition available.

Name:	bpmc_ReimbursableResearchAndDevelopmentCostsRecognized
Namespace Prefix:	bpmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Related to research and development costs incurred under the research plan, the percentage of funding for which the collaborative partner to the reporting entity is responsible per the collaborative agreement.

No definition available.

Name:	bpmc_ResearchAndDevelopmentCostsIncurredUnderResearchPlanCollaborativePartnerFundingPercentagePerAgreement
Namespace Prefix:	bpmc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the current amount of unbilled accounts receivable, including reimbursable research and development costs.

No definition available.

Name:	bpmc_UnbilledReceivablesIncludingReimbursableCostsCurrent
Namespace Prefix:	bpmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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

The amount of consideration recognized during the period for the milestone or milestones.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 28
-Section 50
-Paragraph 2
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=68058744&loc=SL6892177-166501

Name:	us-gaap_RevenueRecognitionMilestoneMethodRevenueRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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=63488584&loc=d3e20235-122688

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Name:	us-gaap_TypeOfArrangementAxis=bpmc_RocheCollaborationAndLicenseArrangementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis=bpmc_ExerciseOfLicenseRightOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_CounterpartyNameAxis=bpmc_RocheMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis=bpmc_PriorToExerciseLicenseRightOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis=bpmc_ExerciseOfLicenseOptionProductNotCommerciallySoldMember
Namespace Prefix:
Data Type:	na
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Name:	us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis=bpmc_ExerciseOfLicenseOptionProductCommerciallySoldMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_TypeOfArrangementAxis=bpmc_AlexionCollaborativeArrangementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	bpmc_MilestoneAxis=bpmc_PreclinicalMilestoneFirstLicensedProductMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	bpmc_MilestoneAxis=bpmc_DevelopmentMilestoneFirstLicensedProductMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	bpmc_MilestoneAxis=bpmc_DevelopmentMilestoneSecondLicensedProductMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: