Marketable Securities - Impairment (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Marketable Securities
Marketable debt securities, charges for credit-related impairments	$ 0	$ 0

Debt Securities, Available-for-sale, Credit-related Impairments, Charges

No definition available.

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