Represents the number of tranches or structured financing of the debt agreement.

No definition available.

Name:	bpmc_DebtInstrumentNumberOfTranches
Namespace Prefix:	bpmc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The fee payable, expressed as a percent, on total loan advances on a credit facility.

+ References

No definition available.

+ Details

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

- Definition

The prepayment fee, expressed as a percent, on outstanding principal at the time prepayment on a credit facility, high end of range.

+ References

No definition available.

+ Details

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

- Definition

The prepayment fee, expressed as a percent, on outstanding principal at the time prepayment on a credit facility, low end of range.

+ References

No definition available.

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ 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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The cash inflow from bank borrowing during the year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bpmc_TermLoan2013Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_PrimeRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bpmc_TermLoan2014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Term Loan - General Information (Details) - Secured Debt $ in Millions	1 Months Ended					3 Months Ended
	Nov. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)	Jun. 30, 2013 USD ($)	May 31, 2013 USD ($) item	Mar. 31, 2017
Term Loan
Percentage fee payable on total loan advances at end of loan (as a percent)						4.00%
Percentage fee payable on outstanding principal in event of prepayment of loan advances, low end of range (as a percent)						1.00%
Percentage fee payable on outstanding principal in event of prepayment of loan advances, high end of range (as a percent)						2.00%
2013 Term Loan
Term Loan
Maximum borrowing capacity					$ 5.0
Number of tranches \| item					3
Proceeds from term loan		$ 2.0	$ 2.0	$ 1.0
2013 Term Loan \| Prime Rate
Term Loan
Fixed rate based on percentage points added to base rate (as a percent)					2.00%
2014 Term Loan
Term Loan
Maximum borrowing capacity	$ 5.0
Proceeds from term loan	$ 5.0